Expansion on t&g boards


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Established Member
13 Apr 2012
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Hope someone can help with this. I’m half way through making some sapele gates for the side of my house. Frames are all put together and now it’s time to board them up with v-notched t&g boards (in sapele). Boards are to run vertically and there will be ten on each gate, approx. 85mm wide. The sapele has been air dried to around 15-20%. I’m just wondering how much gap would be advisable to allow for expansion on each side of the board?
Leave about 2mm between each board,the old way I was taught was to place a spacer between each one of about that thickness,I will say though that sapele is fairly stable and contraction and expansion rates are not that high in my experience.Of course if the gates/ doors are very exposed increase the gap to3 mm,hope this helps.Dont forget to finish the tongues before assembly or when shrinkage occurs they will look awful.Regards Kevin.
Remember that this is the wet time of year. Expansion occurs as they get wetter, but they are not super dry now and I doubt they will expand much more but they will contract in summer sun.

I have never used sapele for this kind of thing (just instrument stringing) as I made my gates from Iroko. They were made and hung in summer with wood at approx 12% in my barn and I used a 2mm gap in quite thick t&6 boards. In this biblically wet weather the gaps are almost closed and they will not get wetter than this. Each gate is about 2.6 metres wide from memory.
Thank you both for your responses. I had figured for about a 2mm gap, but nice to have it confirmed.

That’s a good tip regarding pre-finishing the tongues Kevin. I probably wouldn’t have thought of that.

Thanks again.

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