Warping Decking Boards

[AlGBarker]

Hi guys,

I've just finished my decking ready for the summer, but now the sun has come out I've noticed the boards are starting to arch and warp in the heat. My decking design also includes some planters that are constructed using horizontal decking boards for the sides which are skew screwed from the back onto a frame and the warping is pulling the screws out!

Has anyone got any nifty tricks how I can stop this warping from happening? I wanna get a least one BBQ out of it before my decking pulls itself apart!!

Thanks all,

Alan

 

[pantsmachine]

Unlucky mate, sounds like you were sold unseasoned decking. If its not too big a deck i'd unscrew the lot and stack it for a month or 2 then relay it. What sort of support structure is underneath it and how is it spaced?

 

[Thermo]

you wont stop it doing it. where did you get it from?

 

[regsmyth]

I think I agree with pants.
If it isn't properly dried out before you fix it, it will move. But once it's properly dry, it should remain fairly stable and not cup excessively.

 

[AlGBarker]

Thanks for your comments.

Firstly, if anything, I have over engineered the support frames under the decking. All support joists are no more than 400mm apart and are mounted on a sub frame with concreted support posts every 800mm. You could probably park a car on it and it wouldn't budge!

Secondly the board themselves were from a decent timber merchant. As I wanted the decking to last I avoided the kind of decking you get from B&Q and such like. The odd thing is that the wood was all delivered last August 2009 so plenty of time to weather the boards.

The main floor area of the decking was actually completely at the end of September 2009 but it's only been the last couple of weeks since the sun has come out that this 'cupping' has occurred

It's all very annoying!

 

[Thermo]

boards will move and cup as they dry out in warm weather, but they shouldnt really move that much. what length and type of fixings did you use?

 

[pantsmachine]

Where on the boards did you fix, not one screw in the centre?

 

[AlGBarker]

the length of the longest boards are 4000mm end to end. They are 28mm thick so used 60mm long decking screws and screwed two per joints about 20mm or so from the edge of the boards.

I did notice that they had flattened slightly yesterday evening after they had been rained on a bit and cooled so had the opportunity to re-tighten the screws I'd put in.

I think part of the problem was that I didn't want to over tighten the screws in the first place. I tightened them level with just under the surface of the boards which may have allowed them more movement.

I'm still a bit nervous that when the sun pops out again it'll do the same and pull the screws through even deeper.

 

[bathjobby]

What size gap did you leave between each row of boards ? The deck needs plenty of room to breath and allow for expansion (without the boards touching) and contraction as they go though the cycles of getting wet and then drying out.

 

[Thermo]

yes they will move again unless they are fixed down tightly. they will always expand and contract with teh humidity and temperature, thats why you need to screw them down!