Solid Wood Worktop Installation when bowed

We have a 40mm solid wood beech worktop fitted in our U-shaped kitchen. Two lengths and a third breakfast bar.

The kitchen and wooden worktops were bought and delivered a year ago. Due to various reasons (including my own slow DIY skills) we have only now got to the point of fitting the worktops.

The worktops were stored in the garage originally but only for around a month before they were bought inside. On unpacking they was varying bowing / twisting / cupping on all three. Not overly severe but enough to mean the butt joints would not be exactly level in place.

Due to not having the right tools (and also not having fitted solid worktops before) we employed someone to cut and fit the worktops. He has cut all the worktops to length and also the cut-outs for the sink and hob. He initially did this a week ago and agreed he would come back yesterday to tighten up the butt joints after the worktops had had chance to settle and to see if the bowing / cupping would settle. I also weighted down the high points of the worktops over the last week to see if this would allow the wood to relax back to being level.

After a week it is now evident that the worktops have improved and are not as bowed as they were initially. Yesterday our fitter came back and has siliconed the butt joints and bolted them together (should they have been PVA'd?). As there is still some twisting and bowing he used some packers under some cupboards to allow the butt joints to be bolted together. He has not screwed down any of the worktops to the cabinets as I can do that (I have the right brackets with the slots running perpendicular to the grain). Though when I do this I will be either having to put more packers in so the brackets meet the worktop or screwing in and pulling the worktop further away from where it should be.

The butt joints are sort of OK but not as tight as they could be and are slightly raised in places. The fitter suggested they could be lightly sanded to bring them level.

Whilst I sort of understood the reasoning at the time I am now not convinced that this was the best course of action. In one of the worst areas near a butt joint there is a 4mm packer. For one, the worktops are now no longer level as they are packed out differently across the level worktops. Two, surely over time the worktop will potentially move more but because the packers are in place it will mean the worktop moves further away from true not closer.

I would have thought that it would have been better to try and get the worktops back to being level again. So no packers, release the butt joints, weight down the areas that are bowing upwards and potentially where the worktops are cupping upwards screw them down at the back and then clamp the front and slowly tighten them over a few weeks to bring them true.

Is this a good course of action and if so how easy will it be to separate the already siliconed butt joints? Or has the fitter taken the best course of action with the packers and we have the best outcome we are going to get?

I have included a few photos.

I appreciate any advice! Thanks in advance!!

Daz

 

I could take months for the tops to stabilise now they are out of a damp environment, no point doing anything with them until then.Possible ruined by the time in the garage.Should have been stored in the house a month or two before installing.

 

As detailed in the original post they were stored in the house. They were in the garage for about a month and the last 11 months they have been inside. So they are not from a damp environment.

 

A month in a garage is enough to ruin them.

 

Thanks for all your constructive help.

 

Wood will shrink and swell with changes in moisture. It will only develop stresses if the drying is too fast, or if movement is restrained. Otherwise if it is dried back the original manufactuered moisture content where it was flat, it will recover. Basically the tops should have been re-conditioned before fitting, as otherwise you get what you have.

So whatever you do going forward, you want to make sure the tops have reached equilibrium so that whatever you do is final, don't bother mucking about until then.

What you suggest is reasonable and silicon won't act as any kind of bond.

If you do have to clamp them flat, fixing must still allow for in-service movement or the tops will split.

If you sand the joint flat, you must make sure they are now fully re-conditioned, or they will 'unbow' and you will have dips where you sanded away.

 

its heat and damp that move wood. I've seen 18" wide solid table tops with a 12mm bow (straight edge across the face gives 12mm gap beneath in the middle of the leaf) that when you place 24" away from a hot radiator on edge with the face thats bulging toward the rad - the leaf goes flat within 2 hours. If your tops have curled upwards (bulge underneath) try creating some heat inside the cabinets (fan heater on low) and see if they pull back. But do it carefully and keep checking every 15 mins.

 

That is terrible advice.

Excessive fast drying can cause stresses in the timber, which is what you want to avoid.

Timber is hygroscopic and will shrink and swell with changes in moisture content.

Heat introduced in such a manner will cause an unbalanced moisture content between faces, let it acclimatize properly and don't entertain such a bodge of a method.

 

the guy is looking for clues as to what will solve the problem, if it can be established that heat will pull the top back a bit then leaving them in a room with typical warm temperatures may achieve just that except that it will, as said, take months to find this out. Doing as I suggested will tell you how likely waiting months will give a successful result. I am guessing the OP would like to know now what is the likely result of any fix rather than wait 3 months for the answer. In the same way as I described the table leaf - you wouldnt work on that leaf straight away once flat but you would know what acclimatising it could achieve. Another thing, no one knows the environment of the OPs kitchen - old property with units up against cold outside walls?

PS
looking at the pics, If there is fresh plastering around the walls adjacent to the units this will give out alot of moisture into the underneath of the tops potentially causing them to expand on that reverse face thus making them curl up on the top.

 

Forced harsh drying like that is a bodge, not going to say otherwise.

Drying should be done with care to avoid stress, not a blow heater.

Air movement yes/

 

ok, I'm not gonna argue over this, lifes too short. Just a quick question - my comparison with the table leaf - heating the leaf up in this way enables one to see whether a warp can be made straight with a change of temperature and you can see the results of this within an hour not 6 weeks so why not apply same theory to the guys worktop or are you saying such treatment to a table leaf is a bodge?

edit
sorry I wrote an earlier post and cancelled it but it posted here as a draft

 

Timber shrinks and swells with changes in moisture content.

If you rapidly dry one face, you will cause that face to shrink, potentially pulling the whole piece flat or causing a reverse of existing bow. However, this could cause stress and damage in the process, a risk of splits, and give you a false impression of how it will stabilise when the total thickness has acclimatized (rather than the surface fibres).

The other reason timber bows is due to the difference in tangential and radial shrinkage in the cross section causing unequal stresses, if the timber is through sawn and was planed flat at a particular moisture content, then it will recover to flat if dried to that same moisture content (unless you introduce new stresses through poor drying).

The whole thickness needs to be dried to equilibrium before remedial work, your method will cause uneven moisture contents.

Your advice is bad and you don't know what you are talking about, this is basic stuff covered in any timber drying manual.

 

dont you mean would ?

seems to me the top is buggered and the OP is one step away from replacing therefore any option worth a try......

I notice no mention of the potentially damp plaster kicking out moisture into the cabinets

how is the OP doing with this now I wonder??

 

No could, nothing is certain.

Very proffesional opinion.

 

I think the technical term is that it has 'Failed Under Continuous Testing.'