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.
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.
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.
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!