I've got a slab (concrete) floor.  Nice and solid, but with just tile on it
it is cold in the winter, and wet (from condensation) in the summer.  I've
heard that carpeting doesn't really help the moisture, either.

What I'd like to do is put down some kind of wood or insulation (up to 1/2"?)
so that the floor surface tends to be more in line with ambient inside
temperature, rather than acting as a very effective heatsink by conduction
to the earth underneath.

Any ideas or recommendations?  

19 responses total.

Tough problem, with the condensation concern.  I have a large walkout basement
with doorwalls and windows.  We have glued on 1/2" oak parquet flooring and
it has been down for many years - probably close to 20 yrs.  The glue was
applied to the entire floor with a toothed trowel and the tile was just set
in place and pressed down.  This way, no concrete floor is directly exposed
to the atmosphere and we do not have any moisture problem in the summer.  We
do tend to keep the lower doors and windows closed and the back of basement
(non walk-out portion) is dehumidified)  

This floor is quite comfortable summer and winter.  we have forced air heat
coming up through the floor with a separate furnace for the basement.  

I've been thinking about wood flooring anyway.

The original asphalt tile and my replacement vinyl tile both seem to conduct
heat quite well, so I suspect that even 1/4" of plywood would make a big
difference.  More than 1/2" and I have to muck about with outside doorframes.

I just got some lit. from and outfit out in Mason that makes and sells 3/8"
hardwood flooring.  They also sent me a sq. ft. worth or samples.  Looks
like good stuff.  You may want to give Launstein Hardwoods a call at
517-676-1133 and talk to them about your situation and their product.
Their prices are pretty reasonable too.

Slab floors I've had responded to vapor barrier (tar or plastic), some
insulation barrier, and surface covering.  There are some nice almost
berber type indoor outdoor carpetings that are very durable.  Noe's
floor coverings gave me good advise (and prices) on one floor.

OK, tomorrows project is to put down a new floor in the 2nd bedroom.  What
I am going to do is 1/2" of plywood, with vinyl tile on top.  I'm actually
going to use 2 layers of 1/4" plywood, so that I can overlap the pieces,
gluing them together, and not have to connect to the concrete at all.  

Wood-type coverings were going to cost about $4/foot, way out of my range.
This will cost about $1.50/foot (commercial tile), last a couple decades, and
look fine.  Bonus:  I can have a lot of fun mixing colors and making patterns.

Carpet would also be possible, affordable, and work on this base, but as long
as I have my cat "Pukey Dave", I'd just as soon have rugs I can pick up and
clean or replace.

<<smile>> My cat has been dubbed "The Yak-Meister", and I feel the same way
about rugs.

You could also skip the plywood and vinyl.  Get real, ceramic, tile for $2.50
/ sq. ft. and lay it right on top of the concrete.

I need insulation, though.  Otherwise it is cold in the winter and wet in the
summer.

Researching possible toppings for the drywall we have laid down in the attic
as a floor.  US Gypsum did not like several of Jim's ideas.
1.  Do not put portland cement over drywall, it will react with the gypsum
and degrade it to some other chemical form.
2.  Do not paint over the drywall to prevent this reaction.  The latex paint
will rehydrate and peel off the drywall under the portland cement.
3.  Do not plaster directly over drywall, the paper will swell and then shrink
and the plaster will then come off.  Use rocklath under ordinary plaster
(thick coat) or blueboard under veneer.  Or plaster bond.
We do not want to use veneer as it is too hard to work with, but he suggested
a retarder to slow it down.

Suggestions (other than plywood) were Gypcrete (the company will call back,
apparently you can buy the dry mix and mix it in pails and pour it out) or
Durabond 90 joint compound (over bonding agent?) or lime plaster.  Nobody
likes lime plaster because it hardens so slowly, which sounds ideal for us
as we are in no hurry and would prefer something to harden slowly.  There is
also Keene's cement which may have some lime in it added to the gypsum.

Has anyone on grex practice or experience with plaster?  Klaus, do you know
anything about the readymix Gypcrete, and can you pour just a thin coat over
drywall substrate?  You said it was durable stuff.

Jim has only a couple days of drywall cutting and pasting left.
Klaus, can you drop off that piece of gypcrete from the driveway?

Gypcrete is always mixed on site.  It is mixed with sand much the same
way as concrete.  I do not think that it comes in a ready-mix form. (It
would be mostly sand.)  It has the consistancy of pea soup and sets up
in about an hour.  It is not as tough as contrete but a little tougher
than drywall.

I got the same impression when the company called back and left me
a number to call for an installer, not a place to buy the stuff.
Progressive Building Materials said you can plaster over drywall with
structolite (the stuff with perlite aggregate) and go over with a finish coat
of Diamond.  Or gauging plaster with lime added.  The book talks about lime
putty with gauging plaster added, 2:1.  The plaster keeps the lime from
cracking as it dries, and helps it set faster.  Gypsum plaster is harder than
lime plaster.  We are about to run an experiment with old woodfiber gypsum
plaster over:  plain drywall, painted (latex) drywall, and drywall with pink
bonding agent (designed for brick and concrete to help it bond to plaster).
Nobody seemed to know quite how to approach horizontal walls and kept talking
about make sure it set fast enough not to slip off the wall.  I think we could
probably get by with a ratio of more than 2:1 lime to gypsum plaster.
One 100 pound bag per layer should do it easily (the books talks about square
yards per ton).  Wish us luck.  If this works we may plaster the walls too.

We are running an experiment with old wood fiber plaster and old imperial
finish plaster over painted and unpainted drywall, with and without sand in
the wood fiber plaster.  Supposedly you need two coats, maybe the top coat
is something less likely to crack?  It is whiter, may have more lime.
The latex paint was dry to the touch very quickly.  Jim is finishing up the
last two drywall boards tonight and we have to order plaster soon.
Maybe the lime plaster cracks in thicker coats (the base coat is thicker) but
cracks less in thinner coats?  It has no sand in it, perhaps that makes it
more likely to crack but easier to paint and wash?  If so we don't need a
finish coat for an attic floor.  Nobody can tell us reasons.
Jim comments that there do not seem to be any books on do it yourself
plastering, this takes a lot of practice to get right.  I am considering
paying for the wall plastering if we ever get that far.

CBM says it could take up to month to get us two bags of wood-fiber plaster,
which the guy I talked to had never even heard of, nor had Progressive
Building Materials.  Jim just did a sample patch of latex paint mixed with
sand as a protective coating.  It could always be plastered over later, say
next summer.  We cannot plaster in cold weather.  We know the paint will stick
to the drywall and sand is dirt cheap.

Results of our tests:
Painting the board first with latex paint helps with adhesion, particularly
when the base coat contains sand, which sticks better to paint than to paper.
The base coat, wood-fiber and gypsum, brownish-grey, plaster is much harder
and more resistant to denting than is the white, lime, topcoat.
The topcoat is less hard but more flexible and is more resistant to scratches,
which explains why you first put on a thick coat of sanded gypsum plaster to
prevent dents, covered with a smooth coat of lime plaster which resists
scratching.
Our latex paint mixed with sand crumbles, but resists dents.  It will do under
a coat of scratch-resistant lime finish plaster.

We will experiment with walls.  USGypsum claims you have to buy their special
rocklath wallboard in 2x4' sheets, expensive, because it has paper that does
not absorb moisture and swell.  We may be able to just use regular wallboard
and coat it with latex paint first, but they said something about the paint
getting rehydrated and losing adhesion.  Worth a try, anyway.  Our sample with
paint-gypsum plaster-finish lime plaster is adhering okay.

The paint and sand mixture was not very hard at first but is getting much more
durable, in fact it feels like portland cement already.  If you break off a
piece, the outside crust is very hard and the inside still soft, but Jim is
plastering over it now anyway since we need the warm weather to plaster in.
It takes about one gallon paint, mixed with lots of sand, to do 30 ft sq.,
but the paint is all free, people thank us for taking it from them.

I did something similar once.  I mixed some sand into paint to apply to steps,
so that there would be some traction.  Never heard any complaints, although
it has been a few years and maybe what I did has long since failed and been
reviled.  ;)

Would oil paint also work with sand?  And would this work horizontally?
We are considering doing the interior walls the same way, obviating the need
to buy plaster and rocklath or blueboard.  Except for the finish plaster. 
It seems as dentproof as gypsum plaster already, the sand is what gives it
this quality I think.  No visible cracks yet.  We will see next spring.
Paint would be much more expensive if purchased new, but not if free.

How did your walls and unusual floor work out?

The attic floor is holding up okay except the paint is peeling in the area
over the porch, where the ceiling is not insulated and is therefore colder
than the porch (which is glazed and heats up in the sun).  Moisture must be
getting through the drywall and getting trapped under the paint.

We have not done the walls.

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