Got a sagging wooden door or gate? Building a new one? Not sure how you should brace it? Confused about the conflicting advice you may have read elsewhere? Read on.
Wooden doors and gates come in many different shapes, sizes and styles. A very simple one would look something like this:
Unfortunately, if you build it that way, it will soon end up looking more like this:
The weight of the door/gate has transferred to a relatively small number of nails/screws that hold the wooden boards to the horizontal rails, crushed the adjacent wood fibres, and now the door/gate is sagging. Your door/gate may already look like that.
To repair or prevent sagging requires that the door/gate be braced. A brace is a diagonal piece of wood that takes a bit of the load off the nails/screws.
Tension Braces
Many doors/gates have tension braces. They look like this:
A tension brace works by transferring load from the outside end of the bottom rail to the inside (hinge) end of the top rail. It ‘pulls’ the weight of the gate up to the top hinge.
Compression Braces
The other — and now far more common — type of brace is the compression brace. They look like this:
A compression brace works by transferring the load from the outside end of the top rail to the inside (hinge) end of the bottom rail. The weight of the gate ‘rests’ more on the bottom hinge. Load is transferred something like this:
So, which is better? How should you brace your door/gate?
Tension vs Compression
Let’s kick off by just clarifying one thing: Any type of bracing is better than no bracing at all. Pretty-much all doors/gates require some form of bracing, but depending on size, shape and weight, you can sometimes get away with very little bracing and the type of bracing doesn’t really matter. Narrow and/or light doors/gates fall into the ‘it probably doesn’t matter’ category.
If your door is wide and/or heavy, however, then you are better off with a compression brace. A compression brace is easy for most DIYers to construct to a satisfactory standard, and is hard to screw up. Just remember:
- Compression braces are suitable for doors where the angle between the bottom rail and the brace is greater than 45°
- Make sure both ends of the brace have full contact with the rails
- Put (ideally two) nails/screws through each board into the brace
Note: It is entirely possible to tension brace a wide and heavy gate — if you have a decent amount of experience with different types of joints and you know what you are doing. The average person, however, doesn’t have that experience, and doesn’t have the required carpentry skills…
The biggest advantage that compression braces have over tension braces is the way that loads are transferred. In compression, loads are distributed over the end cross-section of the brace as well as the screws/nails — that greatly reduces the overall rate of fibre compression (which means it will sag less and last longer). Because the loads are transferred to the bottom hinge, and the bottom hinge is closer to the ground, the gate ends up more stable — it bounces up and down less. Gate posts supporting tension-braced gates also tend to bend/twist over time — because the load is transferred to the top hinge (higher from the ground, where it exerts more torque).
Why The Contradictions?
If compression braces have such a clear advantage, why do some sources still recommend tension braces?
Mainly due to historical reasons, but also because in a very limited number of scenarios tension is still better.
In the good old days, farmers and homesteaders would cut their own timber/lumber with axes and saws. The wood would be ‘green’. Green lumber (i.e. freshly cut or anything that hasn’t been kiln-dried or seasoned for a couple of years) contains a large amount of water. As it dries it shrinks. The shrinkage will occur in all of the lumber’s dimensions, but the dimension affecting sag the most is length. The lumber will get shorter. If you are using green lumber, a tension brace is ideal because the shrinking wood will help pull the bottom rail up.
Since nearly all lumber used nowadays is purchased from a store, and has been seasoned/kiln-dried, it contains very little water. If you live in a climate with a wet season, the lumber will absorb water and expand. It will get longer. If you build using dry lumber, a compression brace is ideal because the expanding wood will push the top rail up.
In the good old days, steel wasn’t used for gate posts. Timber posts were sunk into bare soil. Since most gates were outside and exposed to the elements, rain would hit the gate from both sides. A compression brace would channel water that hits the ‘back’ of the gate down towards the gate post — where it would saturate the soil, encourage rot, and result in the premature failure of the post. A tension brace would channel water away from the gate post — helping to keep the soil there dry and prolonging the life of the post.
Modern gate builders often use steel gate posts sunk into concrete, and don’t expect their gates to last a generation, so don’t care where the water goes when it runs off the gate. It’s not even a consideration. If the brace is out of the weather (e.g. the inside of a barn, shed or house door) then it’s also not an issue.
Summary
When would a tension brace be acceptable, or even advisable?
- Narrow doors/gates
- Light doors/gates
- When using green lumber, which includes:
- lumber you have sawn/milled yourself
- (store-bought or reclaimed) lumber that has been exposed to rain
- In exposed situations where the gate post is subject to rot
- If you intend to always keep the door/gate painted/oiled (the brace won’t lengthen during the wet season because water won’t get absorbed in any appreciable amount)
- If you want — or are prepared — to use a turnbuckle brace, then tension is the best/only way to go
In all other situations, the average DIYer would be better off installing a compression brace. If you’re not sure, install a compression brace.
Anyway, I hope you found some of that interesting or useful. Cheerio!
tp69 
I see a lot of modern looking horizontal cladded gates with out a brace. I’m planning on building one, but Curious if solid joinery will compensate for lack of bracing, or how these gates are designed to eliminate the need for a brace.
Many ‘modern’ products are designed with planned obsolescence in mind — they are designed to fail and thereby promote replacement and new sales. Products are not inherently ‘better’ by virtue of being ‘modern’. That said, good design, materials, manufacturing and assembly can — definitely — deliver a door/gate that doesn’t sag appreciably over time and thus does not need a dedicated bracing element. Expect to pay a pretty penny for one, though.
Compression and tension braces, as described above, are easy and cheap ways to keep low and medium-quality doors and gates — installed by the average Joe — functioning the way they are supposed to. Turnbuckle tension braces are also a relatively easy and discreet way to fix a gate that promised more than it delivered.
After trawling through the Internet trying to research which direction would be best to add a brace for a 3’7″ gate ( slightly wider than normal I suppose), this is the ONLY detailed explanation I have found to help me decide.
I will now be adding a compression brace .
Thank you for this information.
Glad I could help Ahmed.
A person built my gate with only a turnbuckle. Its already sagging. I will use the turnbuckle. But do I need a compression brace also?
Bobbie, turnbuckle-braced gates and fences usually sag a little in the first year as wood fibres compress and components settle in. The good thing about turnbuckles, though, is that they can be adjusted. If you haven’t already, just tighten the turnbuckle until the gate is back in the desired position, and then leave it for another year. It is not uncommon to have to turn the buckle quite a few times in the first year, a few more times in the second year, a small amount in the third year, and then very little (if any) after that.
If you have reached the limit of how far the turnbuckle can be tightened, you can always stick something under the free end of the gate to support it, loosen the turnbuckle as far as you can, then disconnect one of the cables, shorten it, reconnect it, then tighten up the turnbuckle again.
Without seeing the gate, it is impossible to know if it has a fundamental design flaw that is causing it to sag. If a “professional” installed the gate, however, then it’s probably not fundamentally flawed, and just needs some tightening. I don’t advise adding any more bracing until you’ve had the gate (and kept adjusting the turnbuckle) for a minimum of three years. If it still keeps sagging significantly after that, the reason it is sagging should have become obvious (e.g. wood tearing, plate slipping, post bending). Then you can either fix the problem or install more bracing.
I have more of a question than a comment.
I have a 10′ x 12′ shed in my back yard. It has a single door that measures 52″ x 72″. It has 3 horizontal braces on the outside. It’s pretty much a rectangle with one horizontal 2×4 in the middle. There are 3 large “T” hinges holding the door to the shed. The door has sagged about 3/4″. With the door being divided into two sections, what would be the best type of bracing to help prevent the door from sagging again ? Once I get the door square again, of course.
Thanks for your assistance.
Karl, your best bet is to install one compression brace in each section (from outer top corner down to inner bottom corner). Something like this:
Would have a compression as well as a tension brace, ie a cross brace with the intersection rebated and securely screwed together further strengthen the gate? Thanks
Wilson, if you are suggesting a cross-brace for Karl’s situation, then I don’t think that would be a good idea at all. He describes his door as being a rectangle with a horizontal 2×4 through the middle. If you tried to add a cross-brace to that then you would have three pieces of wood all crossing at the same point and they would need to be cut very thinly indeed (very deep rebates). Since the strength of a brace is proportional to cross-sectional area, any reduction in thickness (i.e. any form of rebating) reduces the strength of a brace.
If you weren’t talking about Karl’s situation, and are talking about cross-braces in general (no horizontal framing in the middle), then the same logic applies, but you end up with 50% depth rebates, and lose half of your bracing strength, instead of two-thirds. Not quite as bad, but still bad.
Although I (personally) like the look of cross-braces, the reality is that they don’t (mechanically) work as well, which is why I don’t use them.
A tension brace is good if your lumber is green/wet, so that when it dries it pulls tighter. If you make both parts of a cross brace out of the same lumber, or planks from the same stack of lumber, then they will have similar moisture levels. If the moisture level is ‘high’ then your compression brace will shrink and weaken the door. If the moisture level is ‘low’ then the tension brace will expand and weaken the door. So, no matter what the moisture level, some part of the bracing system is going to malfunction. A lose-lose situation.
Because I don’t want any part of my doors or gates undermining the rest, I like to keep their designs simple. Stick with one type of bracing if at all possible. If the visual appearance of double compression bracing on a door is a problem, I’d rather add a thin veneer of some sort to the sheltered inside. Something like a 3mm sheet of plywood wouldn’t add much weight, but would make it look nicer (IMHO) — and might even help stiffen the door up a bit.
Note: All of the above refers to wooden cross-braces. If you have metal bracing then a welded cross-brace is perfectly fine. Metal is not affected by moisture levels in the same way that wood is.
What Ahmed said.
I (a physics major in college) had convinced myself that t didn’t matter which way the brace ran, but Maine Cabin Masters said to have it run to the bottom hinge. So I searched the internet for an explanation, found several not-very-helpful or not-very-convincing how-to’s, and then found this. Excellent explanation. So my *next* z-back door will have a compression brace, unlike my first one.Thank you!
Eromer, I’m glad it helped clear things up. Good luck with your next door!
I’m building a small wooden gate which will be wider than it is tall. Should I use a compression brace, but keep the angle 45 degrees such that the brace will not span the entire width?
Zach, if you are going to make the effort to brace a gate then you may as well brace the full width. In the case of gates that are twice as wide as they are high, the best approach is to switch from one gate to two. For gates that are not quite that wide, or when two gates aren’t a viable option, the simplest approach is to use two compression braces side-by-side instead.
The first brace extends from the bottom rail near the bottom hinge up and out diagonally until it meets the top rail. Drop straight down from that to the bottom rail and start your second brace there. The second brace then goes up and out until it meets the top rail near the outside (free) edge of the gate. Basically, a saw-tooth pattern — and essentially the same pattern that gives trusses their great strength.
Assuming your gate is symmetrical, the top of the first brace and the bottom of the second brace should contact their respective rails near the mid-point of your gate. That should make both brace angles identical — something most folk prefer the look of.
Gates that are three times as wide as they are high should really have steel bracing, or a turnbuckle tension brace. Gates four (or more) times as wide as they are high should be made entirely of steel, not wood, with saw-tooth bracing all the way — basically they become trusses at that point. You can make quite wide gates entirely out of wood, but only if you design and build them like commercial and industrial trusses. That’s a non-trivial task beyond the capability of most DIY folks.
Thanks a lot Tim. After some other research I was leaning towards the 2 parallel braces as well.
Hi Tim,
Thanks for this useful article. I love that you are still answering questions on it after 2 years. I am planning to make a hidden gate out of featheredge fencing so that it is indistinguishable from the rest of the fence on the public side similar to the example at http://www.greenshave.co.uk/gardengalleryfancyafence.html
The hinges and bolts will be fixed to a small section of rail cantilevered from posts 8″ either side of the gate with a 1:4 cantilever backspan. I was planning to use a double-z compression brace to reinforce the gate as there are three horizontal rails and no vertical framing. However, the person who installs these hidden gates suggested I run the diagonals from the top and bottom of the hinged side of the gate, meeting at the middle on the bolt side of the gate. After searching online it seems this is called a ‘British brace’ although I have also seen it with the hinges and bolts on the opposite side to what is described above. I wondered if you could explain what are the advantages of this system, if there is any particular benefit to me for my specific usage and what side the hinges and bolts should go on?
Kind Regards,
Greg
Greg, there are precisely zero technical advantages to the “British Brace”. Indeed, assuming that all the braces start with the same moisture level, regardless of whether the weather is wet or dry, one brace will always always be undermining¹ the integrity of the gate. A “Double-Z” (double-compression) brace, made from seasoned/dried timber, does not do this — so is technically superior.
The reason the British Brace exists is nationalism. The shape of a British Brace forms one half of the Union Jack (the flag of the UK). If you have two gates, with the same design on both, you get a full Union Jack. That’s it. That’s why the design exists. No other reason.
As has been the case throughout all of human history, when design is driven by nationalism instead of functionality, you end up with an inferior product. The British Brace is no exception.
The farmers of old recognised the liability, which is why back in the day you would usually only see the design on barn doors — sliding doors — that were hung from a top rail, not hinged from the side. Sliding doors barely need bracing at all, so a cosmetic brace design isn’t a liability in such a use-case.
Physics recommends that a side-hinged gate with three horizontal rails should be supported by two compression braces. Go Double-Z.
¹ Assuming you start with dry timber, in the wet season the timber will expand and lengthen. The top brace of a British Brace — extending from the inner side of the top rail to the outer side of the middle rail — will try to push the gate down towards the ground. This is the exact opposite of what you want bracing to actually do. All bracing should work to counter the effects of gravity, and should either pull or push the outer side of the gate upwards. The rule-of thumb for side-hinged gates: ‘Up and in’ is good; ‘Down and out’ is bad.
Thanks Tim,
I really appreciate it. I wish there were more forums like this as helpful as yours. Now to try and persuade them to do it the proper way, I know ‘professionals’ don’t like being told what to do!
Regards,
Greg
Brilliantly useful article. Thank you.
May I ask your opinion please. When using a Z brace (compression) is it functionality important that the angle of both braces is the same? The situation is where the middle horizontal rail is not centered i.e. it’s nearer the top or bottom rail. The angle of both braces will be kept greater than 45 degrees so that rule won’t be broken. Cosmetically it’s not important to me as the back of the door will be skinned with 3mm ply.
Thanks in advance
Dave
Dave,
Each section (top and bottom) of a Double-Z brace design is, effectively, independent.
Load transferred by the top brace should be directed through the middle hinge into the post. Load transferred by the bottom brace should be directed through the bottom hinge into the post. This holds true provided that the bottom/inner end of each brace rests on the part of a rail that is also directly attached to a hinge — which is almost always the case.
Brace angle symmetry is not required when sections are independent.
PS: A Double-Z design with three horizontal rails but only two hinges (i.e. the middle rail is not hinged) is sub-optimal design that should be corrected. Hopefully this does not apply to you, and all three of your rails are hinged. If only two hinges support three rails, then the top and bottom sections are not truly independent and… well… the physics becomes surprisingly complicated at that point.
Thanks Tim,
Yes sorry that’s exactly what I meant, a Double-Z design with three horizontal rails 🙂 You make a good point about the need to hinge the middle rail!
I didn’t mention it but I’ll be using stiles. I assume the addition of stiles (so becoming a framed, ledged and braced door) would lessen the need for three hinges because the load from the top brace would transfer down the stile to the bottom hinge? Or could the same load, unsupported by a middle hinge bow the stile over time and cause its own problems!?
Thanks
Dave
Hello Tim, I hope this note finds you in good health.
I have a gate that is 36″ by 36″. That is, the rails are 36″ long and the slats are 36″ long.
The difference between the bottom of the top rail and the top of the bottom rail is18 3\4 “. When I cut my brace on a mock up using old lumber for the rails and the brace in order to make my mistakes there instead of when I use the pressure treated lumber, I noticed that the angle from the bottom hinge to the top latch was quite a bit less than 45 degrees, which would make the transfer of power quite weak.
I decided to make two braces and attach them equidistant from each other. In this way, the angle was greater than 45 degrees. I haven’t put it together yet because I wanted your opinion on whether it was a good idea to use two braces instead of one long brace.
Thanks Tim
James in Ottawa, Canada.
James, apologies for the delayed response — was out of town and offline for the good part of a week.
If what you are planning is something like the following image, then you’ll be fine:
Note that the top of the inner brace and the bottom of the outer brace are connected to the same vertical board/slat. While this is optimal from a load transfer point of view, some folks prefer them to align with adjacent boards — usually because they have an even number of boards, not an odd number. Adjacent boards are acceptable if this is the case.
David, stiles (vertical timbers on the inside and outside edge of a door or gate) do not have the positive effect that most folks think they do. If the stiles are in addition to the normal boards — which is typical, and appears to be the case by your use of the word ‘framed’ — then your gate will sag slightly more than a gate with no stiles at all. The reason is simple: Weight. You are adding mass to the outer edge (the worst possible place as mass there generates the most torque). The inner stile accomplishes nothing, as it is directly connected to all of your hinges. Load can’t be preferentially transferred down to lower hinges because, to do so, it would have to bend the hinges higher up. Since metal beats wood, that doesn’t happen — load just distributes over all hinges evenly.
From a structural point of view, constructing a frame that looks like the number 8 on a calculator’s segmented display, and then cladding one side with planks will stiffen the gate. This makes it more resistant to things like wind and mechanical forces like animals trying to slip out, or trespassers trying to force the gate open. If you want added security, it’s not a bad idea. It makes a gate more secure at the expense of added weight.
To offset the additional weight, folks sometimes add small braces to the outer corners. Do an image search for ‘gate corner brace’ to see what I mean.
At this point complexity has gone up a few notches, and we’ve strayed from the original intent of this post: Guidance for DIYers with average carpentry skills on how to make simple and functional gates that won’t sag.
‘Bowing’ is not something you should be concerned about. That (unfortunately) happens when folks don’t pay attention to the grain of their boards, and too many boards end up with the same, non-parallel side grain. If your boards have parallel side grain your gate won’t bow. If your boards have non-parallel side grain, and you alternate their direction, then warping forces will cancel out and your gate won’t bow. ‘Randomly’ selected and assembled boards (which is what typically happens when folks aren’t even aware of the bowing issue) rarely end up in a configuration that bows the gate.
Thanks Tim: Excellent explanation.
I never thought about that i.e. “Note that the top of the inner brace and the bottom of the outer brace are connected to the same vertical board/slat. I did, however, upon reviewing your responses, see the explanation for Zach.
BTW, How to add an image? Copying and pasting don’t work.
James in Ottawa, Canada
James, WordPress comments are limited to text. You can’t paste images into a comment. What you can do, however, is upload an image to your own website, or some image-hosting site, and then include the URL for that image in your comment. Put the URL on a line by itself and it will render without a hitch.
Hi Tim, I require three three horizontal rails on my gate to attach the featheredge rails to. However if I were to use a double-Z configuration the angle would be less than 45 degrees. What are your thoughts on a diagonal brace that runs from the outer top corner to the inner (hinge side) bottom corner ‘through’ the horizontal rail in the middle (when I say through I don’t mean this literally as the brace would be constructed of two separate pieces of wood and screwed into the middle rail). Also in this scenario would a third hinge have any benefit?
Greg, if the middle rail of a 3-rail gate is unhinged, it is basically cosmetic — it contributes very little to the structural integrity of the gate and is of little value in preventing sag. What is much, much more useful (as in, nearly an order of magnitude more useful) is a single, unbroken, diagonal brace that runs between the top and bottom (hinged) rails.
Consider the option of fabricating a single (top to bottom) brace, then dry fitting it, marking the sides of the point where it crosses over the middle rail, and then carefully cutting a diagonal slot out of the middle rail so that the brace can slot into the cut-out section. Cutting a primarily cosmetic unhinged middle rail has virtually no down-side. Adding a full-length brace has a huge up-side.
If you do the above, then the length of middle rail that can be hinged has been roughly halved, so there is little point in adding a hinge for it (many/most of the boards an additional hinge would support are already directly connected to two steel hinges, and thus aren’t going anywhere anyway).
If (for whatever reason) you want/need to keep the middle rail intact, and are going to cut the brace instead, then cut the two small braces as carefully as you can, so that you end up with full cross-sectional contact with all rails, and add a hinge to the middle rail. That won’t make your gate as sag-resistant as a single, unbroken brace would, but it will be better than what you have now.
I believe you have an error in your post. Wood mostly shrinks in width as it dries, hardly at all in length.
Great post otherwise.
Ron, whilst the statement “wood mostly shrinks in width as it dries, hardly at all in length” is correct, “hardly at all in length” is actually something and, indeed, enough to matter when bracing doors and gates. There is no error.
The longitudinal shrinkage rate of wood tends to be between 0.1% and 0.3% with hardwoods on the upper end and softwoods on the lower end. If we take the middle (0.2%) and apply it to a small, square (2x2m) barn door, then the difference between dried/wet wood used correctly/incorrectly as a brace is an end sag of roughly 16–17mm. That’s about 11/16ths of an inch in the old measure.
So, whilst longitudinal shrinkage is (relatively) small, even small rates matter when building doors and gates. The bigger the door or gate, the more it matters. In my neck of the woods, 16–17mm gaps can let in four of the Top-10 most venomous snakes in the world… and I’ve already lost too many good dogs.
The amount of acceptable sag is ultimately up to the individual to decide based on their unique circumstances. I figure that most people end up here because their door/gate sags too much. Appreciating how drying and wetting impacts performance will let some of those folk build/brace their door/gate to sag less. The physics is sound.
PS: In the article the sentence that probably prompted your comment was this one: “The shrinkage will occur in all dimensions, but most noticeably along its length.” That sentence wasn’t trying to assert that the most shrinkage would occur over the lumber’s length. It was trying to say that the dimension whose shrinkage would produce the most noticeable effect was the lumber’s length. In other words, tangential and radial effects are not as noticeable as longitudinal effects. I think I will edit the article and phrase that better to avoid future confusion. My apologies for the ambiguous/misleading wording.
Hi Tim,
Thank you for such a thorough explanation. I want to make sure I understand correctly: I will be building a gate that is approximately 3 feet by 8 feet high (deer fence) made out of 1x4s or 1x6s. I was planning on using a horizontal crossbar right in the middle of the gate. Then I was planning on running 2 z-braces, one going from the top outside corner to the middle inside hinge and another running from the middle outside corner to the bottom hinge. I was going to get regular wood from home depot and treat it with green stuff so it doesn’t rot. Three questions: 1). Would this type of design help it from sagging? 2). Is 1×6 ok to use structurally or should I use 2×4 for the whole thing? These are going to be outside. They are garden gates. 3) Do I even need a horizontal bar? Can I simply run 2 Zs without the horizontal bar? Thank you in advance!
Lara,
1) Yes, a double-z bracing pattern transferring load through three hinged horizontal rails is a very good bracing option for a 3×8′ gate.
2) Either 1×6 or 2×4 will be sufficient as long as you don’t put cladding on it that is too heavy. If you want to err on the side of caution, use 2×4 braces as they are about a third stronger under compression. We have a small amount of deer in our neck of the woods. Never seen one inside the fence though. They do not strike me as the sort of animal that will challenge any sort of gate they can’t see through or peek around. So if deer are you only concern, focus on making a gate with no ‘peekable’ holes in it.
3) Tall narrow gates are served really well by compression braces, so purely from a bracing point of view, you do not really need a middle rail. That said, a middle rail does stiffen things up a bit (which is nice for reasons mentioned in earlier comments) and it gives you a great place to mount a sturdy latch or bolt. If you want this gate to pose any sort of obstacle at all to human intruders, have (and hinge) a middle rail.
Tim, thank you for your reply! I really appreciate it! I wish I could post pictures here after I build it.
Lara, you could always upload an image to your WordPress site, then in the Media section select the image, click on Edit, and on the right hand side (might have to scroll down) you will have the option to Copy the URL. Do that and then paste the URL into a comment here — on a line by itself — and your image will will be visible in your comment.
If you do this, try to keep image dimensions (and thus file size) reasonable — doesn’t need to be more than about 600px wide.
Alternatively, make a post on your own site then just post a link to it in a comment here.
Good luck!
We live in a converted stable in Buckinghamshire England on a farm with buildings over 300 years old. My son today (17) noticed that some of the old wooden doors had braces going one way, others in another way and new and old gates (wood and steel) a mix of cross directions. Thanks to your incredibly insightful article we can now make sense of it all. The rain on gates and the use of green wood considerations really made sense. Although why the wooden garden gate (20 years old) has both tension and compression braces is a mystery to me! Great article. Thanks!
Kevin & Finn, I’m glad I could help you ‘read’ your property better. The old-timers generally had a very good understanding of the fundamentals — something I feel we lost as society moved off the land and into cities. Ah well. Enjoy the stable!
PS: The garden gate with both compression and tension braces was either a) designed/built by someone who didn’t understand how bracing works, b) designed by someone who appreciated cosmetics (i.e. the look of crosses) more than functionality, or c) originally only had one brace, sagged, and then had the other brace added to (hopefully) correct the problem.
Hi Tim.
Just great that you continue to reply to comments on this page.
The brace on the garden gate is like this:
Although in our case the braces meet at the latch side not the hinge side.
I’m assuming it’s an aesthetic choice rather than structural
Kevin
Kevin, if your gate has hinges similar to the linked image then I wouldn’t worry about the bracing being sub-optimal/aesthetic. A 3×6′ gate with steel hinges that extend half the length of the rails shouldn’t sag much at all. Bit too much (shiny) metal for my taste, but each to their own. Otherwise a tidy-looking gate. Thanks for sharing!
Hi Tim, how do you recommend to attach the brace to the rails? Screw and glue? How many? And from what direction? Also, if I used the design here https://www.secrets-of-shed-building.com/building_a_shed_door.html could I do away with screws altogether?
Greg, the simplest way is to put a long screw diagonally through the tip of the brace and into the rail. (A drill bit extension helps — especially if your boards are thin.)
All you are trying to do is prevent horizontal slippage — which is minimal if you keep the rail-brace angle above 45° anyway. The vertical forces are what make compression braces work, so you don’t need to do anything in the vertical plane.
Most glues tend not to last too long outdoors, so I don’t personally bother. Add some if you like — won’t hurt.
If you are willing to chisel out a notch as per the link you provided, sure, you can do away with screws and glue entirely. Or combine the two approaches, if you like!
I would advise against excessively-complicated (‘fancy’) joints or removing too much material from the rail. A single screw, or a 5mm notch, will get you over 90% of the way to ‘optimal’.
Okay, thanks. I was planning a double-z brace but I’ve run into a problem in that the angle would be less than 45°. I’ve just measured the gate rails which are 38mm x 88mm and they are 612mm apart. There’s nothing much I can do about this because I am cutting the gate out of a fence and then hinging it onto the rails (they are cantilevered on the fence posts with a greater than 1:4 backspan). I have three rails and three hinges (I don’t have to use the third hinge if it is not necessary) and I don’t want the width of the gate to be less than 800mm. Now I’m scratching my head about what to do. I could do a top to bottom brace but this would involve cutting the middle rail so the middle hinge would be pointless and would weaken the structural integrity of the gate as it is just ledged and braced (there is no frame). I could do a top to bottom brace, cut at the middle rail but this would be less effective. Another two options I considered were to decrease the horizontal span of the double-z braces so that they are 45° or use the notch method above so that the angle would not matter so much. What are your thoughts?
Hello:
“Put (ideally two) nails/screws through each board into the brace.”
If you are saying that EACH vertical board/slat, which attaches to the rails, should have two nails/screws put into the brace, wouldn’t that be unsightly? Or, are you saying that nails/screws, should be angled into the top and bottom of the brace where the brace meets the rails in order to secure the brace from shifting. I hope this makes sense.
James, if you look at my response to Greg a little bit earlier, you will see that I suggest an angled screw (not a nail) and/or a small notch to fix braces to rails. That should prevent the vast majority of any horizontal slippage that may happen to the brace.
The main reason to use nails/screws to bond the boards to the brace is to stiffen the gate. (It does improve slip resistance a tiny bit, but the amount is almost inconsequential compared to a screw+notch combo.) If your gate is in an environment where kids may swing on it, where intruders may climb over it, where animals may challenge it, where branches may fall on it, where vines may grow on it, or where strong winds may buffet it, then the stiffer your gate, the better.
Every nail/screw you add between boards and brace improves stiffness — up to a maximum of two nails/screws per board. You enter the realm of seriously diminished returns beyond two, so it’s not recommended to exceed that amount.
“Unsightly” is a matter of personal preference, and cannot be judged by physics or maths. I, personally, love the look and feel of sturdy gates. I die a little inside when a flimsily-built gate flexes when I open or close it. Each to their own. If your environment is relatively tame, and doesn’t justify a particularly stiff gate, you could definitely reduce the number of nails/screws between boards and brace. How much by is up to you.
NB: If you don’t have any at all, your brace has (basically) a 50% chance of bowing out (determined by grain orientation) and if it does, then your gate will sag.
Hello Tim:
I took a look at my gate and I see what you mean about grain and bowing. I put two deck screws into each spot where the brace meets the vertical boards basically shortening the brace length and, subsequently the grain length : about 8 screws. Good call!
James (and anyone else who may be interested down the track), if you have a 2-rail gate with a compression brace, and that brace bows, then the bowing will occur either along the plane of the gate (assuming your gate is hinged on the left that would be left and up, or right and down) or out (away from the boards). While the actual length of the brace doesn’t necessarily change in any of those scenarios, the straight-line distance between the ends of the brace will be smaller. So assuming the brace has been fixed to the rails with screws, it will be pulling the two rails together. Since the brace should be fixed to the bottom rail near a steel/iron hinge, that end should not budge. What will move is the other end — the outer end of the top rail will be pulled down… and with it the free end of the gate. That’s why not screwing boards to braces can result in sagging.
If the grain orientation of the brace would have it bow into the gate (i.e. towards the boards) then the boards themselves obstruct and reduce the bowing. No gap appears between the brace and the boards, and the actual amount of bowing tends to be negligible. Unless you know what to look for, you’d barely even notice it’s happened. In most cases the this type of brace bowing does not result in noticeable amounts of sag.
To mitigate the whole bowing effect, nails/screws should be used to fix boards to the brace at the time of initial construction.
If the brace was not fixed to the boards during construction, and months/years have passed, and the brace has bowed, then what you should do to fix the problem depends on the direction of the bowing: If bowing was outward (away from the boards) then just screw the boards to the brace and the brace will straighten right out. Easy. If, however, the bowing was along the plane of the gate, then simply screwing the boards to the brace will prevent further bowing and sagging, but will not undo the bowing and sagging that has already occurred. To undo that you would need to straighten the brace before you screw the boards to it. In some cases, this might not be possible. Using a ratchet strap is perhaps the easiest way, but be careful not to over-tension it and rip one end of your brace out of the rail it is screwed into.
Hopefully this extra level of detail will be useful to… someone. 🙂
Wow, how thorough can you get?
I think I caught mine in time. I don’t see any bowing along the plane/grain of the gate/brace and the gate locking mechanism is not out of whack. It closes very easily.
Tim, thank you for your time. Great stuff man.
Can anyone help with the geometry? If I know the distance between the rails, the length of the horizontal rails and the breadth of the brace timber, how do I calculate the angle of the mitre? I could lay the gate flat and then lay the brace timber across the rails in order to mark it up in position for my cuts but it would be more convenient to calculate the solution.
Steve, assuming no offset for a notch (i.e. you want the tips of the brace to line up with the ends of the rails), let:
rL = rail Length
dBR = distance Between Rails
bW = brace Width
Back-of-envelope math would suggest:
bL (brace Length) = sqrt( rL^2 + dBR^2 – bW^2 )
mA (mitre Angle (in degrees)) = 180/pi * ( pi/2 – arctan( dBR / rL ) – arcsin( bW / sqrt( rL^2 + dBR^2 ) ) )
Cut brace to length bL. Mitre back opposite corners by mA.
Let me know how you go. 🙂
NB: The mA equation above assumes that you are operating in “radians mode”. Spreadsheets do this by default. If you are using a calculator, switch it from DEGrees mode to RADians mode. The result of the equation will be in degrees (thanks to the 180/pi multiplier).
Greg, sorry for the late reply but your second comment slipped through the cracks. Mea culpa. Although it is probably too late to be of any use, here are my thoughts anyway:
Notches should be considered to have but a single function: Stop horizontal slippage of the brace. Unless the notches are extraordinarily deep and tight, they do little to offset the problems caused by small brace angles. As such notches introduce new complexities and problems of their own, I would not advise pursuing that line of thought. “Here be dragons.”
“Hinging it to the [cantilevered] rails” also really concerns me. It sounds like the part of the hinge on the fence side will be bolted into sections of exiting fence rail, as opposed to a post. If that’s the case, then red flags go up instantly. Without a post to directly hinge to, a gate is fundamentally structurally compromised. Unless you address that situation you are guaranteed to have problems down the line. Problems that will make the issue of bracing pale into insignificance.
If I were you — and assuming I have correctly interpreted your situation — I would add another post to the fence to act as a gate post. With that post in place discussion of bracing can proceed and actually be meaningful.
I got the feeling that wanting to keep and make use of the middle rail/hinge was an opinion influenced by the ‘fragility’ of the proposed hinge system. Deep down you knew (or suspected) that hinging to fence rails (instead of a post) was a bad idea, so to avoid making a bad situation even worse you wanted to attach the gate to as many points as possible, and thus devalued options that would compromise the third (middle) rail. No need!
With a new gate post in place, and a secure place to fix hinges to, your first idea is the better one: Cut a slot in the middle rail and run a fully-intact brace between the top and bottom rails. Sure, that makes the middle rail mainly cosmetic, and pretty-much eliminates any need to have a third hinge, but you’ll end up with less sag.
The geometry of your fence is in a tricky grey zone with no good and clear solution. If you want to keep the ‘look’ of the gate as similar as possible to the fence, then it’s the best you can do.
PS: If you have a bit of aesthetic wriggle-room, you could consider adding two more rails — one above the top rail, and one below the bottom rail. If there is physical room to do this, and the brace angles between these new rails and the middle rail would be greater than 45°, then you could hinge 1 (new top), 3 (middle) and 5 (new bottom), cut 2 (old top) and 4 (old bottom), and double-Z brace 1-3 and 3-5. Because you keep all the old rails, it would maintain visual continuity with the old fence. The new additional rails would just make it stand out a little (which, under most circumstances, is OK to do with a gate anyway).