How to fasten kitchen countertop to allow for expansion

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Forum topic by Jake posted 02-10-2014 09:23 AM 1307 views 0 times favorited 11 replies Add to Favorites Watch
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850 posts in 1655 days

02-10-2014 09:23 AM

Hey all. Quick question about fixing a slab of wood as a kitchen countertop.

I am working on my kitchen remodel and I will be attaching my countertop to my cabinets within a week or so, but I am worried about the seasonal movement, because I have not done such a huge slab before. I already made a few mistakes by glueing certain parts on there, which are bound to crack, but whatever, I will deal with that when it happens. :)

Anyhow, I got a 24” x 9’ x 2” Slab of Iroko Mahogany (African Teak) that I have as a countertop and I am worried that at that width it will be expanding quite a bit, so how do I fix it on there to allow for movement?

I was thinking of fastening it in the back and front with screws, like 2 screws per cabinet, so in total I would be looking at 10 screws. I think it will be more than enough since the slab is very heavy, at least 120 pounds. You can see it in my blog here So I think it will be held in place by the weight itself already.

But how does one allow the movement, do I just make an elongated oval with movement of like 1” from front to back and fasten the screw in the middle? I really need to allow for the movement, because with the sink hole in the top I am afraid that if it doesn’t move as a unit, it will break somewhere.

-- Measure twice, cut once, cut again for good measure.

11 replies so far

View jinkyjock's profile


488 posts in 1598 days

#1 posted 02-10-2014 11:11 AM

Hi Jake, have fitted large worktops before and any longitudinal expansion, even over a 9ft. length, is so minimal that it shouldn’t really be of much concern. However across the width is where you need to concentrate. First thing is to ensure is your worktop is well sealed on BOTH sides to stabilize before fitting. You can buy expansion plates fit for purpose, or just cut slots as you thought and use a washer under the screw. DONT take the top straight from a cold workshop into your kitchen, and if you can cut the sink hole before final fitting to allow you to seal it, particularly the end-grain cut. Good luck, I am sure you will be fine ‘cos you’re asking all the right questions.

View Jake's profile


850 posts in 1655 days

#2 posted 02-10-2014 12:00 PM

Thank you for the tips jinkyjock!! yeah, the longitude expansion doesn’t bother me one bit.

Quick questions in regards to what you suggested:
1. By well sealed, what do you mean? I was thinking of going with 3-4 coats of BLO, don’t really want to use a varnish of any kind.

2. In terms of the cut out, can I still cut it in my workshop and then bring it up and leave the whole thing for a few days and then seal it, or should I bring it up to warm up, and then cut and seal it after it has warmed up?

3. Should I cut the holes for the sink and stove a bit oversized? If so, how much would you reccomend? The last thing I want to do is have my granite sink to be broken by the expansion, those damn things aint cheap.

-- Measure twice, cut once, cut again for good measure.

View Monte Pittman's profile

Monte Pittman

29386 posts in 2362 days

#3 posted 02-10-2014 12:07 PM

That’s how I do table tops also. I call it “floating” because it isn’t fastened tight. Helps avoid splitting and if you’re gluing pieces together it won’t let them tear each other apart.

Good luck on your project and be sure to post.

-- Nature created it, I just assemble it.

View Fred Hargis's profile

Fred Hargis

4999 posts in 2517 days

#4 posted 02-10-2014 12:09 PM

Consider using these for you elongated holes, they really work well.

-- Our village hasn't lost it's idiot, he was elected to congress.

View jinkyjock's profile


488 posts in 1598 days

#5 posted 02-10-2014 12:48 PM

Hi Jake, by sealing I mean applying whichever finish you choose. You may leave final coat till after installation if you are using oils. I usually apply finish then cut holes, sometimes cuts have to be made in-situ ‘cos you may weaken top & then handling becomes an issue. You should have some sort of template for hole cuts which allow for movement, unless it’s something like a Belfast sink which has no lip to cover cutout. You should try to acclimatize the top as much as possible & apply “extra” finish to any exposed end-grain. Sorry I can’t be more specific but it’s very much play it by ear.

View Jake's profile


850 posts in 1655 days

#6 posted 02-10-2014 01:04 PM

Awesome, thanks for all the additional information, you guys rock.

I understand what you mean by now. I will have to see with the hole cutting. With the weight of the top I am very much worried about weakening it before transport as well, but I am also worried that if I cut the holes after all the sanding to 1500 I will make marks on the finished top. And the Iroko dust is a PITA, my fiancee coughs like crazy whenever she comes into the shop and I have some of that dust flying about.

I coughed as well, but I am getting used to it now, but I think cutting it upstairs in the kitchen is out of the question. So I probably will have to make the cuts in my mancave, make them like 3/16 larger to allow for movement up to 6/16 altogether.

Then I will sand that sucker down to 1500, apply generaous amounts of BLO to endgrain, like 3 coats on the top itself, clamp some boards on it to help with the transport, take it upstairs and then leave it to acclimate for a few days. After final assembly I will put on another coat and hope it works.

Could I also apply the BLO while sanding it or does that just clog up my dry sandpaper? What about when i go to handsanding with wet/dry, could I be applying BLO while sanding, or is there even any point to do that?

-- Measure twice, cut once, cut again for good measure.

View jinkyjock's profile


488 posts in 1598 days

#7 posted 02-10-2014 01:15 PM

Hi Jake, am on my lunch at the minute, couple of Q’s. By BLO do you mean linseed oil, do you have ANY extraction for when you’re sanding?

View chrisstef's profile (online now)


17423 posts in 3030 days

#8 posted 02-10-2014 02:12 PM

I sued figure 8 fasteners in a 3/4” hole to attach the countertops I just recently finished. The 3/4” hole is slightly oversized in comparison to the fasteners which should allow it to move around a little bit. The BLO on a countertop kind of scares me though. You’re not really providing a film finish to protect the countertops from spills and stray water. I went back and forth between Waterlox and Arm-R-Seal and chose the latter. General Finishes also make a water based top coat, Enduro Var or High Performance I believe.

-- Its not a crack, its a casting imperfection.

View BentheViking's profile


1782 posts in 2588 days

#9 posted 02-10-2014 02:19 PM

I’d see if you can track down a type of L-bracket made for this. It will have an vertically elongated hole to fasten to the sides of the cabinets and a front to back elongated hole to fasten to the countertop. screw it in, but not too tight or it won’t allow for movement.

-- It's made of wood. Real sturdy.--Chubbs Peterson

View dhazelton's profile


2771 posts in 2321 days

#10 posted 02-10-2014 03:04 PM

That would be heavy enough to just screw along the back of the length and put silicone along the front. It’ll never go anywhere.

View Jake's profile


850 posts in 1655 days

#11 posted 02-10-2014 03:07 PM

Alright, I’ll see about those l brackets. Yea I intended to use linseed oil. I am in Europe so most of the brands you guys recommend are usually not available for me. As an added bonus I am also in a small country with limited options and most importantly – limited knowledge. :)

But generally speaking what should i use as the top coat then. Because i was under the impression that BLO would be good as it is food safe and very easy to apply and if something awful happens I can just re sand and apply.

Any recommendations are highly appreciated!

-- Measure twice, cut once, cut again for good measure.

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