Wood Expansion Question

[brianhabby]

I have been asked to make a pair of garden gates for a friend and am not sure how much to allow for expansion of the wood.

The gates will have a field of T&G. I am making them from softwood bought from my local builders yard. After making the gates they will be disassembled and sent back for pressure treatment. Then I will store them for a couple of weeks before re-assembly.

The T&G timbers will be about 5" x ¾".

I've seen what can happen in these situations when no allowance is made for timber expansion so my question is - How much is the wood likely to expand?

I don't want to have gaps appear between the boards in the summer any more than I want the gates to seize up in the winter :?

regards

Brian

 

[mailee]

Hi Brian, I usually leave round 1/4" at each end to allow for this on softwood gates. I use one brad top and bottom in each board and space the ends 1/4" in. So far I have had no complaints about my gates. :wink:

 

[9fingers]

My garden shed door which has no provision in its design to cope with expansion and contraction is about 3 foot wide and 'grows' in winter by about 1/4" so that is a bit under 1%.

Bear in mid that when your boards come back from pressure treating they are likely to be wringing wet so depending on how long you can afford to let them dry, you will be assembling with components at maximum size.

hth

Bob

PS making a decently designed shed door is one of my round to it projects!

 

[SBJ]

What you have to realise is that timber movement occurs across the crain and not (well not significantly) along the grain.

If the stiles on your gates are the same width as the stiles on Bobs door then you could reasonably expect that Bobs experience might well be the same as yours irrespective of the overall width of the gate. You also have to consider the prevalent conditions when you assemble the gates, if the timber is still quite wet then you might expect that you dont get considerable expansion, but in the heat of the summer you end up with large gaps where there used to be timber! For the panel, as mailee says, if you put a pin in the centre of each board you should be Ok.

 

[brianhabby]

Thanks guys,

I will be making them with dry timber and will have to try to make the correct allowance for when they are wet. I was told by the suppliers to wait about two weeks for the timbers to dry but I suspect that may be a little optimistic.

I'll leave them indoors with a de-humidifier on for as long as possible when they come back from being treated.

regards

Brian