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[Shop-talk] Oak floors on a concrete slab - LONG

Subject: [Shop-talk] Oak floors on a concrete slab - LONG
From: kvacek at ameritech.net (Karl Vacek)
Date: Tue, 18 Oct 2011 17:37:33 -0500
>From: Scott Hall

>Subject: Re: [Shop-talk] Appliance rollers  <snip> I'd love to hear 

>more about the hardwood floors on a concrete slab.  Did you glue them?

I researched quite a bit before doing the floors, and what we did worked out
well.  The final installation technique was pretty unique, but it began with
recommendations from the several wood flooring trade groups.

 

I first ground any notable high spots in the slab.  Then I installed a layer
of WR Grace ice and water shield - a roofing product.  It's a sandwich of
interleaved layers of bituminous and polyethylene.  Very tough, sticks in
place and to itself along seams, and when nailed through (on a roof or
shooting concrete nails to secure a floor) it seals to the nails.  I believe
that this far better than a typical layer of plastic sheeting - it's really
impervious and won't tear through or shred as old plastic will.  And I ran
it up the walls a couple inches to cover the gaps where drafts used to blow
in.

 

Then I cross-laid two layers of 1/2" CDX plywood.  The initial plan was to
glue and screw the two layers together and let the whole floor float.  The
guy I hired to lay the first couple of rooms agreed to do as I planned until
he started the job, then he ragged on me till I agreed to let him nail the
subfloor to the concrete slab.  We still glued the two layers together, with
Titebond.  I don't think anchoring it to the slab was a bad thing, since the
floors are completely silent to walk on with no springiness or creaking, but
I do think that a floating floor would have expanded and contracted as one
unit better.

 

After that it was a straightforward installation - nailing into nearly 1" of
plywood gives a good anchor.

 

Regrets:

- I was sold on the Swedish finishes, and we used Synteko.  Never again.
It's hard and scratchproof, but rather than soak into the floor like a layer
of urethane, it forms a hard film on top of the wood.  Then it cracks over
the grain and in joints.  Urethane after we resand (soon) - I want flexible
protection that bonds into the wood.

 

- I tried to anticipate all the sub-slab work we'd need, but I didn't think
of running a few conduits under strategic areas, for later electrical or
plumbing additions.  Too late now.

 

- Much of the floor is quarter-sawn.  Though quarter-sawn wood expands and
contracts less width-wise than plain-sawn, we have significant end-gaps in
the quarter-sawn areas, even though everyone knows that wood shrinks very
little length-wise.  The plain-sawn areas don't have an end-gap problem.
Might be because I wanted the oak in really long lengths.  I couldn't get
over 4' in the plain-sawn wood, but the quarter-sawn runs up to 7 and 8
feet.

 

Karl

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