warped luan help

[Bob Riefer]

When I rebuilt the kitchen, we decided to carry the flooring into the entry way for consistency sake. The subfloor in the kitchen was taller then the entry way floor by exactly the thickness of a piece of luan.

The kitchen subfloor is plywood over floor joists.

The entry way is concrete slab with ceramic tiles on top.

My method was to use some liquid nails and glue the luan down in the entry way over top of the ceramic tiles.

Well... the glue didn't hold and the luan has warped badly. Now, every time I walk into my beautiful new kitchen, it pops when I step there. There's at least an inch of space under the warped sheet now. GRRRRRRRRRR.

Now, luckily, we had a vinyl floating floor put in, so I can easily roll it back to fix the problem.

My question is... When I recut my fresh luan to install it, is there a specific glue you'd suggest? Do you recommend that I additionally use tapcons to mechanically fasten into the slab? Any other tips?

Thanks!!

[Bob Riefer]

I win a door prize if I stump the creek right?

[charlie knighton]

Bob, you might try Staybond, RTV silicone sealant, SRTV,Mil-A-46106A Type 1
remains tough and flexible
bonds to wood, glass, metals and plastics

i do not know where to buy large quanties, John Lucas on AAW board uses it to bond mirrows to wood, the wood will move with mositure changes but the mirrow will not move

[Jim Creech]

Bob,
From what you have said I suspect your problem is due to the luan expanding due to moisture in the slab area. Because the wood is popping up tells me there is no room for it to expand laterally. When replacing the luan you might want to consider cutting a series of kerfs about 2" apart to allow room for the wood to expand laterally as it absorbs moisture. Make certain to allow a gap around the edges also. As an alternative you may just cut a bunch of strips and space them about 1/8" apart. Either should solve the problem. My son lives in a slab built house with parquet floors and has had a similar experience. We tried the method described in affected areas .We also used Liquid Nails as an adhesive. So far , no problems.
Hope this helps.

[Mark Major]

Bob, just a suggestion, but I'd consider ditching the sheet goods entirely and look into floating that area of the floor with a polymer modified self-leveling cement.


Regards, Mark

[Craig Matheny]

I am not sure of the name but there is a polymer adhesive / chalking that is used on cement tilt up buildings to fill the gaps and it works on wood also White Lightning® 3006TM Ultra All Purpose Elastomeric Sealant is one choice it allows for expansion from the wood and the concrete

[Bob Riefer]

Thanks guys!

I had considered that the luan might be in there too tight... but then I thought back to luan I've seen over the years. It's always butted up tight to the next sheet in all directions, isn't it? Else it wouldn't provide a good surface for linoleum/vinyl flooring (bc the gaps would telegraph through).

I think it's possible there's a slight moisture difference between the slab and tiles as compared to the wood floor area.

I will try those more flexible adhesives that were suggested, and use mechancial fasteners as well. I'll use some thinset as "mud" to hide the screw heads before I lay the vinyl back down. Sound reasonable?

[Jeremy Brant]

A sheet of luan should be the same thickness as the thin hardiboard. The hardiboard would not be affected by moisture through the slab the same way as the luan. I would consider using a modified thinset with a v-notch trowel and laying in the hardiboard.

[Bob Riefer]

That's a great idea, thank you! I will definitely check that out. I am not looking forward to trying to drill into 70 year old concrete, and this would get me around that issue.

edit: Can I cut the thin hardi board with standard tools or do I need a specialty blade?

[Ron Conlon]

I used to work with a woman named LuAnn, and the title of this post just made me laugh.

[Peter Stahl]

The way you can check for moisture is lay a piece of plastic where the Luan was and if there is moisture under it then you have a moisture problem. Using concrete backer board like someone suggest but the thinset might not stick to the existing tile. Go to a real tile store and ask them what they would suggest.

[Jeremy Brant]

That's a great idea, thank you! I will definitely check that out. I am not looking forward to trying to drill into 70 year old concrete, and this would get me around that issue.

edit: Can I cut the thin hardi board with standard tools or do I need a specialty blade?

Sorry, just got back to the post, so you probably already tackled this. You can cut the thin hardi with just about anything. A deep score and snap like with drywall will work. I've also used a cheap circular saw blade, a diamond blade, a jigsaw, an angle grinder with a masonry blade, and probably a couple other "this is what I have, let's make it work" methods. If you go with a circular saw or angle grinder, I'd advise using a dust mask or respirator as it will produce bigtime airborne dust.