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I built a shed door last summer and have had a few problems with it since.

Using pressure treated outdoor timber I made a fairly simple shed door. I wood glued the long planks together and then used four straight braces across the back that I glued and screwed into the long front planks. I then painted the door with standard shed type paint (Ronseal)

All seemed fine at first until winter hit where the front planks in the middle started to come away from the braces, but also to push out at the top so it was deformed and the door would no longer close properly. It made quite a gap between the second and third long planks when it was perfectly flat together before. I would say it moves anywhere from 1/2 an inch to 2 inches (1 to 5 cm)!

This year it started to go back to normal and the gap disappeared, but as it's got cold again recently it's re-appeared again.

Is there anything I can do to fix the problem? Or should I start again with a new door? What can I do in the future to avoid this issue?

Enter image description here

Enter image description here

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    Welcome to humidity. Or given what looks like very little roof overhang to protect the door, liquid water adding to the effect of humidity. Wood moves as it gets wet and dries again. – Ecnerwal May 13 at 11:38
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    What @Ecnerwal said. In addition - when you do whatever you do, add some diagonal bracing as well, otherwise you'll have a very saggy door before too long. – SiHa May 13 at 11:57
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    Love the door. Bravo! – psaxton May 18 at 13:50
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    Seconding @SiHa... maybe take out the two center braces, and put a piece diagonally across (so you have a "Z" pattern); you could also take the two out and put one dead center, then do a double "Z". – Doktor J May 18 at 14:27
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Welcome to the joys of working with a natural product!

Before I address your construction techniques, I've got to say that is a quite handsome looking door you've made. Well done!

Wood moves. It expands and contracts as temperature and humidity change. It's a "feature" of wood that you cannot and will not be able to change. It's so critical, common and expected that you must plan for it when you're working with wood. As a matter of fact, if you have a dining room table with a solid wood top (not a particle board/press board/chip board IKEA style table top), you can take a look at the underside to see that your table top is not firmly attached to the legs or skirt boards. It's attached loosely so that the top can move with the wood expansion without destroying the table. Usually, a metal clip (though there may be a wooden clip) is slipped into a slot in the skirt board, then screwed firmly into the top. This holds the top firmly down, but allows the clip to slide in the slot. You'll note that there is no glue in sight when it comes to attaching the top to the skirt boards! Now, consider that the kitchen table is inside the house where the temperature and humidity are reasonably stable year round, as opposed to your poor shed door that's exposed to the elements and the full extremes of temperature and humidity swings that your neighborhood experiences. You're going to have to do something similar for your shed door.

You said you built your door in the summer. What's happening is that as the temperature gets colder and the humidity drops during the winder, the wood is shrinking. Since you've very firmly glued those horizontal braces across the back and the strap hinges across the front, the wood has no freedom to move as it shrinks, so the individual pieces start twisting and bowing. It's their only option, and it means your door won't fit anymore. The good news, as you noticed, is that when the temperature and humidity return to near build conditions, the wood returns to its original size and the door fits again.

Wood moves across it's width significantly more than along its length. That is, for your door, it wants to get wider, not taller. Since the horizontal pieces across the back are holding the vertical boards tightly together, there's no way for the wood to adjust itself, so it's warping on you.

The horizontal bracing pieces across the back will want to grow taller (in this orientation), not longer. Since they're glued to the vertical boards that aren't moving in that direction, they'll causing warping of the whole door as they expand.

Fortunately, the fix MIGHT BE fairly simple and doesn't involve any additional purchases (like fancy clips):

  • Take the door off the hinges
  • Remove the horizontal pieces from the back (I'd suggest doing them 1 at a time).
    • This involves not just undoing the screws, but prying them off of the glue.
    • You may end up destroying your horizontal pieces, and may remove chunks from the vertical pieces.
    • When you're done with this process, you'll have full confidence in the strength of wood glue. If you did a good job of gluing (and it sounds like you did), it's gonna be tough!!
  • Modify the holes that the screw goes through the horizontal piece from a hole to a slot.
    • It doesn't have to be a very big slot, maybe 1/4" (4-5mm).
    • You can do this by putting a bit in your drill; putting the bit through the hole; then, while the drill is running, rocking the drill side-to-side in the hole to elongate it into a bit of an oval. The bit used should provide clearance for the attaching screws. That is, it should be just larger than the diameter of the threads. It is the screw head that should hold the bracing on the back, not the threads.
    • Note that you want the slots to be horizontal when the horizontal bracing goes back on. That means the the slots should run along the length of the back bracing, not across its width.
    • This isn't rocket surgery, so don't worry if your slots aren't exactly 1/4" and if they don't match each other in size exactly, or if they're not exactly along the long dimension of the horizontal brace.
  • Reattach the horizontal board to the verticals. You'll want it to be snug enough not to wobble, but not so tight that you're pulling the screw head down into the wood. You may consider putting a washer under the screw head if they were previously countersunk or if your widening also made the slots a bit taller.

Once you've finished this process for all your horizontal boards, rehang the door. It should still feel nice and solid - you did get the screws tight, after all. However, as the wood shrinks come winter, the screws, solidly anchored in the vertical boards that make up the door, will have room to move in the slots in the horizontal backer pieces, thus allowing the wood room to move without forcing things to warp.

An additional consideration

You may will want to put a diagonal on the back of the door, instead of just the horizontal boards. If there is a single screw running through each of those horizontal boards, over time the handle side will want to sag and the boards will be allowed to pivot around that single screw. Since you glued the horizontal bracing on, you probably won't experience sag, but you'll have the warp you already experienced. When you properly rebuild the door without glue, it'll sag. If you attach a board on a diagonal, it will prevent this sagging. In order to avoid rebuilding the entire door (if possible), you could add diagonals in the top and bottom thirds. Just be sure to create slots for the screws going through the new diagonals, not holes, or you'll just shift the problem.


Unfortunately, the fix MIGHT end up destroying the wood (to the point where you'd not be happy reusing it) as you try to break up the glue joints. Glue between the vertical pieces of the front is excellent - it's exactly what you want. The glue holding the horizontal boards cross-grain on the back is probably causing 90% of your problem. If you determine that the wood is no longer suitable to purpose, you're going to have to start from scratch. If that happens, my suggestions are:

  • Build the main door door slab exactly as you did before - edge glue the vertical boards together.
  • Install one horizontal board across the back at the top with screws only (no glue), and make expansion slots through this board as described above.
    • Note that this does not need to be at the very top of the door. You can move it down some for nice visual balance of the brace on the back and the strap hinge on the front.
  • Install one horizontal board across the back at the bottom, the same as above.
    • Note that this does not need to be at the very bottom of the door. You can move it up some for nice visual balance of the brace on the back and the strap hinge on the front.
  • Install one diagonal board between your two horizontals. Again, no glue, and slotted holes (the holes should be slotted horizontally when the diagonal is installed).
  • Reinstall the top strap hinge into the top horizontal back brace.
  • Relocate the lower strap hinge to the bottom of the door so it goes into the bottom horizontal back brace.

If you build in the summer, the wood should be at its maximum width. If the door fits, it will still fit in the winter. It's possible that the slab will shrink enough to allow the bracing on the back to show and may allow water/wind around the door and into the shed. If it's important that the shed remain dry inside, install weather stripping to protect it.

If you build in the winter, the wood will be near its minimum width. If the door just fits now, it will not fit when the wood expands in the summer. Make the door a bit smaller to allow for this expansion. There are a variety of references available online that will offer ranges of expansion for different types of wood (it's a natural product - each tree may expand a different amount). Use these tables to estimate the expansion you should expect and adjust your sizing accordingly.

A thought on those hinges:

They look really nice and I like them - a lot! However, since they're metal, and the metal won't move as much as the wood will, they're going to have the same binding effect on the expansion of the door that the glued on horizontal boards did. Metal will heat and expand during the day and shrink back down at night, so it will move some, but it is very unlikely that it will move as much as the seasonal changes you're seeing in the wood.

You may want to consider using a slightly smaller bolt when attaching the hinges than was originally called for. This will give the bolt room to move in the metal hole as the wood shrinks/expands during the year and you'd end up with the same effect as your slotted holes in the backside bracing.

Optionally, if you can securely clamp the hinge without damaging it, you might drill out the holes to make them slightly larger, then use the original bolts. This would be the way to go if you're able to reuse the door panel after disassembly of the bracing on the back. Smaller bolts won't hold in the old holes from the larger ones. It would also save on the purchase of new bolts, even if you do have to rebuild the entire thing.

A thought on Pressure Treated lumber

PT lumber is always a good choice for outdoor wood work. Bear in mind, though, that when you buy it, it's going to be pretty wet. Sometimes so wet that it will leave some dampness on your hands as you're working with it. Wet wood is big wood and it will shrink over time. If at all possible, buy your PT lumber ahead of time and let it dry out for a couple of months prior to starting construction. That will help reduce the amount of shrinking you'll get in your project.

I realize that this isn't always possible nor practical, but it's something to consider when you're building something somewhat size critical like a door.

One more time:

NEVER glue boards cross-grain. It will prevent the wood from moving and will cause warping.

Well, almost never. One board, glued cross-grain to another board is generally OK up to a certain width. Two 2x4s are going to be OK, two 2x6s are probably good. Beyond that you're going to start asking for trouble. Check those resources for expansion for the species you're working with.

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    Thankyou for the very thorough and detailed answer! I really appreciate that. To ask a question when you say drill a slot instead am i to assume i would use a drill bit a fair bit smaller than the screws and make the slot on the horizontal/diagonal braces. Wouldnt this cause the screws to not hold the wood together becuase the hole is now wider than the screws ? Or am i missing something ? Thanks in advance! – GamerGypps May 13 at 12:58
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    @GamerGypps Actually, you want a clearance hole in the piece of wood being attached. Because this hole is just big enough for the threads to not bite into it, it relies on the screw head to act as a clamp (screws are designed for this). That way, the screw can pull the two pieces of wood together. If you've ever driven a screw through one piece of wood (making its own hole), then into a second piece and had the top piece push up, it's because the threads take a few revolutions to bite into the 2nd piece, but continue to work through the 1st piece. This drives them apart. ... – FreeMan May 13 at 13:26
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    ...The clearance hole means you really start "attaching" (i.e. the threads bite into the wood), in the lower piece. This allows the top piece to "float" until the screw head clamps them together. All that to say, no, you want to use a bit that's a fraction larger than the diameter as the threads of the screws holding this together. You don't really want them biting into the bracing, only the door panel. The goal is to allow the braces to float a bit so that as the panel expands/contracts the screws are free to move across the braces to prevent warping. – FreeMan May 13 at 13:30
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    I see thankyou! Another question, if the screws movealong with the front panels of wood, wouldnt that mean that the brace piece at the back could move left to right and stick out the edge and overhang and potentially get caught on the door jam ? – GamerGypps May 13 at 13:35
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    @GamerGypps If the horizontal bracing is short enough to clear the frame in the heat and humidity of the summer, then it will clear when it shrinks in the winter. Wood does expand in length, but very minimally - it's the width that's the main concern. If you're building in the cold of winter, you'll want to leave a bit of gap to allow for summer expansion. There are resources available online that will give you expected expansion amounts for different types of wood. They're ranges/reasonable guesses because wood is natural and varies from tree to tree. – FreeMan May 13 at 13:40
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In addition to the accepted answer, it would help to add some weather protection. A small rain shield or canopy will help divert weather from the upper part of the door.

Essentially a small verandah to divert both rain and sun from the door without impeding access, and gives you shelter when opening the door in the weather. Awning, canopy, door shelter, are all words to describe this, and probably other regional words too.

enter image description here

If that's too big, a simple flashing or "drip cap" will reduce the ingress of moisture to your door.

enter image description here
from https://www.buildeazy.com/shed-door/


Finally - that's a moderately dark coloured door. Darker colours increase Insolation, which is just fancy-talk for "gets hotter in sun." You should see decreased warping by making the door a lighter colour, though its probably too late given is already stained.

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  • There is an accepted answer? ;) In other news, great additional suggestion. – FreeMan May 14 at 10:37
  • @Moyli Oops, didn't notice the top answer wasn't accepted /: – Redwolf Programs May 14 at 16:31
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Both answers are great, but I wanted to note that you really should be adding a water-proofing solution to the door on a regular basis. As Criggie noted, covering the door would naturally limit how much water and it's exposed to, but the door will still get some water on it.

Water is your enemy in wood because wood absorbs it like a sponge (go to a lumber yard and marvel at how wet their pressure-treated wood is). As it absorbs and evaporates, your wood will expand and contract (far worse than mere thermal expansion) and it will eventually warp and break. Water-proofing adds oils to the pores in the wood that would absorb the water. This limits how much gets in. Most water-proofing also adds UV resistance. Regardless of what you do, a regular regimen of adding it will prolong the life of your outdoor wood.

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wood shed door with diagonal

I think the question of a diagonal is imperative, as is already pointed out in the earlier answers, that I decided to add an image of a wood shed built in the 1950s with a door that still doesn't sag, even after decades of beating from the elements (the hinges have been renewed, though).

It is clear that there are cracks between the individual planks which is the leeway you will need to have for the wood to shrink'n'expand.

In the image you can also see how 4" nails have been used to fasten the planks to one another by turning the nail inward before hitting it home. This technique, in Finnish is called "kotkaaminen", in English it's called clenching, and is a really fool proof method of making an inexpensive and long lasting fastening. The nail hooks into the wood on the back. Using nails gives your wood the clearance to move through the seasonal changes in humidity.

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