I'm using 135mm treated T&G wood to panel a gate. The wood is dry so to avoid it buckling in winter I need to leave a gap. I have left an offcut submerged in water for 3 days and it's expanded 2mm and seems to have stopped. Is this a true guide to its max expansion?
Wood expansion for outside use
- Thread starter Deansplit
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if your offcut has only expanded 2mm when saturated it wasnt dry to start with
the outside may be dry but the moisture content is likly to be around 15% to 20%
try putting an"dry" offcut somwhere continuously warm like under the lagging on the hot water tank for a week
the outside may be dry but the moisture content is likly to be around 15% to 20%
try putting an"dry" offcut somwhere continuously warm like under the lagging on the hot water tank for a week
the trouble is if you assemble now and the wind vertical slope and solar power find another 5mm shrinkage and you have nailed in the tounge rather than the face you will have a rather flappy bit off wood secured at one edge
if you do go ahead secure by one[central] or 2 1/3 and 2/3 fixings through into the back then you wont get loose planks if they seperate
if you do go ahead secure by one[central] or 2 1/3 and 2/3 fixings through into the back then you wont get loose planks if they seperate
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Get a moisture meter if you want to do it properly.
2mm within the tounge and groove, providing the tounge is 8mm, should be fine. If the tounge is smaller than that, then there could be a risk of them disengating in dry weather.
2mm within the tounge and groove, providing the tounge is 8mm, should be fine. If the tounge is smaller than that, then there could be a risk of them disengating in dry weather.
Thx guys - 1st answer - I'm fixing with 1x coach bolt in ea centre, or will that make it curl?
2nd answer - yes, 8mm tongues, but I'm now worried that the 4mm gap I'm planning on leaving will be 2mm too much seeing as the submerged pce has only expanded 2mm. If they 'aren't' totally dry, that extra 2mm should be helping the tongue stay intact when they shrink even more. Wondering if I should take a happy medium - allow 3mm???
2nd answer - yes, 8mm tongues, but I'm now worried that the 4mm gap I'm planning on leaving will be 2mm too much seeing as the submerged pce has only expanded 2mm. If they 'aren't' totally dry, that extra 2mm should be helping the tongue stay intact when they shrink even more. Wondering if I should take a happy medium - allow 3mm???
...actually, I 'do' have a moisture metre - not sure what the readings should be tho - I thought anything over 20% 'inside' a home is classed as damp, but below that is usual moisture content? If I test both the dry pce and the wet pce, what figures am I looking for?
What is the moisture content?
Timber will go from around 10-12% in a dry period, to 20-22% in a wet period, but will spend most of its time in between that (the surface may go up to 25% directly after wetting).
A 4% moisture change will give you a 1% dimension change approx.
If you get the moisture content of what it is now, hopefully the above will tell you how much it will shrink or expand approximatly (A 2mm gap is the norm).
Timber will go from around 10-12% in a dry period, to 20-22% in a wet period, but will spend most of its time in between that (the surface may go up to 25% directly after wetting).
A 4% moisture change will give you a 1% dimension change approx.
If you get the moisture content of what it is now, hopefully the above will tell you how much it will shrink or expand approximatly (A 2mm gap is the norm).
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