Thread: Flattening a bowed / warped kauri pine benchtop

Have you tried flipping it over and see if the sun will bring it back. Seems it wasn't sealed as well as you think.

4 hours in direct summer sunlight would have don't it no favors
Good chance it will settle back into its original shape...BUT it may not!
Pretty amazing the way in which timber moves and adjusts to changes in humidity and heat levels...MM

I would put it back out in the sun with a moisture barrier beneath it, such as a sheet of plastic. Convex side up. Check it every 10 minutes or so, and leave it until the top show surface is slightly convex. That way when it comes to installing the benchtop onto the base cabinets, it will seat nicely around the perimeter instead of rocking on the midpoint.

No I haven't attempted anything yet, I didn't want to make it worse by rushing into it. I did think to start with just flipping it over and exposing the convex side to the sun and watching it very closely, but what is the reason for the moisture barrier as you suggest? Interesting point about trying to make it slightly convex on the surface, though ... I hadn't thought of that

I need to take the sealer off it anyway, so I was thinking to do this before exposing to sun again to make sure it is breathing well all round.

The moisture barrier is probably overkill, but since i have plastic lying around here most of the time its easy for me to do. I figure if i was to lay the concave side (drier side) down against concrete, the concrete will wick away moisture from the already dry side. Can lay the board on grass too and that will probably inject moisture into the dry concave side. I dont have grass at my place, just a choice of dusty weeds or heavy mulch.

Ah OK. The first time around it was sitting on trestles, so I assumed I'd just do that again, but I have plastic and a grass area, so I guess there's options there.

Is the mechanism at work here dehydration of the wood? Is there any chance that these attempts will make things worse?

I have had to deal with a lot of this but in Pine and much thinner sizes. What I do is spray it with water from a hand pump bottle and lay it on a wood floor concave side down. The concave side was directly in the sun wasn't it?

Yes the top side was in the sun and curved upwards on the edges.

You spray it all over or just one side?

Give it a light spray all over then lay it down. In 19mm pine I can stand there and watch it straighten out and it will be flat in 30 minutes but in some cases it takes all night or even another spray. I have had it go to far so rinse and repeat on the other side.

Thanks Chris. It's really encouraging to hear that it might be pretty straightforward to resolve!

So just to clarify ... you're NOT suggesting to put it back out in the sun?

Make sure that the concrete floor is as level as possible. Whilst most floors are essentially flat, you would be surprised at how out of level some floors can be.

Sun is one of timber's biggest enemy. When building I always make sure it's covered or shaded at all times. Just a few minutes on a hot day can ruin a piece. what everyone else says are all good ways of trying to remedy it. Hope you get it back straight again.
Tim

Good news is that I took it out yesterday evening around 2 hours before sunset in the shade and placed it on some tarps on my flat concrete driveway, sprayed the concave side and placed it concave side down. Over about 90 mins it shifted about half the distance back to flat, at which point I lifted it up, dried it off and put it back inside to settle. It hasn't moved any further, so I'll do it again tomorrow evening.

The bench is in 3 panels and I noticed one of the panels a bit more bowed than the others, so I might concentrate the water spray there for the next run.

Originally Posted by simmo35

Thanks Chris. It's really encouraging to hear that it might be pretty straightforward to resolve!

So just to clarify ... you're NOT suggesting to put it back out in the sun?

I don't think that would be a wise move. I do it on my workshop floor which is sheet flooring. I have seen a board go right past flat and bend the other way, apart from swearing it just needs to be repeated on the other side which is no problem. When applying finish do it evenly both sides to minimise the problem. I have removed a finish, wet it to straighten and applied the finish afterwards, all part of the fun of wet weather, hot weather etc.