I am trying to fasten some wooden planks to the concrete
floor in our third storey apartment. The 3 storey building is
built of two by fours in the usual way. Between the storeys
is a layer of featherlite concrete. I have tried #8 concrete
screws and also sheetrock self-tapping screws. Sometimes
these hold but more often the concrete crumbles and will
not hold the fastener securely.
I am writing to ask if there are other ways of securing a
fastener to featherlite concrete. Perhaps some kind of
anchor which will stay in place and hold a fastener.
Thank you in advance for your suggestions.
I'd try either a single expansion or double expansion anchor:
That lightweight concrete is only there for soundproofing and fire
resistance. It is only about 2" thick. Get some screws long enough to
go all the way through to the plywood underneath.
Question: Should you be doing this in an apartment? Are you renting?
The reason that I ask is that those floors are very crumbly to begin
with and any penetrations make them crack even more. I have replaced
thousands of square feet of this stuff. When we are remodeling (in
condos that are built the same way), we usually use an epoxy application
to bond everything together, then glue and attach new wall plate both to
the lightweight (with construction adhesive) and to the plywood
substrate (with screws, mostly to hold in place until the glues dries).
The lightweight cannot be trusted to hold anything, or even to hold
together, without help.
We own the apartment. Of course I don't want to go through the ceiling
of the apartment downstairs so I don't think I should try to reach the
plywood above the downstairs apartment's ceiling.
I should explain further what the project is. I mean to install a
manufactured wood pergo type floor over the wall-to-wall carpet and
subpad which is to be left in place. I want to leave it in place to
decrease any noise transmission to the apt below caused by us walking
around (with our shoes off). I want to secure the pergo floor to the
cement so it wont float up and down when walked on. I know that the
pergo will expand and contract so I have made prevision for some
movement by setting a 1 1/4 flat washer into some of the pergo strakes
with a half inch hole drilled through the strake underneath the flat
washer. A 1" o.d.fender washer rides on the flat washer and through
the fender washer
a flat head fastener secures to the cement. This permits the strake to
move a bit underneath the fender washer and fastener. The fender
washer and fastener slides on the flat washer. I would like to try the
some kind of expanding anchor to see if that would hold. The flathead
fastener is countersunk so only the 1/16" thickness of the fender
washer is proud of the strake. The carpet nap is the springy type. The
fastener just has to be tight enough to compress the carpet. Perhaps a
single expansion or double expansion anchor would work with a flathead
machine screw to expand it. Or one of the many other anchors available
from the Concrete Fasteners company which was referenced in Jack
I might mention that the lightweight has held together for 40 years.
Thanks for your useful comments.
That seems to me like you are asking for major trouble down the road! Does
the manufacturer of the flooring permit installation over carpet??
I would remove the carpet and pad, and start from there. Surely the
manufacturer has a underlayment of some sort for this purpose!
What is the possible trouble? The manufacturer of this product,
Harmonics, does advise removing carpet and underpad and they
do sell a plastic pad to put under the floor. Not to do so voids
their 25 year "guarantee." This might make some sense if one
was installing on a cement slab at ground level where the
hydroscopic nature of cement would buckle the floor in a wet
season. But I am 3 storeys up and there would be a pad and
a carpet between the floor and the concrete.
The moisture is NOT the prime reason for your idea voiding the warranty,
it's the flexing of the "planks" on the current carpet. The pad that they
make for underlayment is just think enough to allow some give and flex, but
not so much as to actually allow the plank to snap.
But what the hell, if you know the product better than the folks that made
it, have fun.
The instruction warn against moisture problems if pad is not
used. Yes, the manufacturers know more about the product
than I do, but I sure as hell know the product better than you do.
What I love the most about things like this is when the guy...yes, I'm
comfortable with that generalization in this newsgroup...ignores the parts
that HE said about the warranty being voided, but I'm the a$$hole that
doesn't know the product.
Oh, well...it's good for a laugh on a monday
Since this guy is in Austin, he may be the same guy that did one of the
weirdest floors I have seen. I was requested to come and replace some
vinyl that had developed holes.
I figured to find some old vinyl that had worn through, but noooooo! I
found a pantry that had been carpeted and the guy had just lain vinyl
over the carpet and used roofing nails to attach it. The nails were
placed on the corners of the pattern and were nearly hidden by the
pattern except that the vinyl was pulled down tight at those points.
Walking on the floor had caused tears and holes (I guess from high
heels). I explained that this was not proper and that I would have to
remove both the vinyl and the carpet if he wanted me to reinstall new
vinyl. He thought that I was trying to rip him off by doing more work
than was needed!
I didn't do that job.
Took me a while to figure out what the hell the floor was in the first
place. It was kind of cool in a way. Real soft vinyl!
The amount of gratuituous abuse from strangers on
news groups is staggering.
2" sheetrock screws are holding tight into the featherlite
concrete. I will tighten the strakes down later when the
flooring is monolithic. The cheap high pile floor-to-floor
carpet just needs enough force to hold its high pile down.
These are Harmonic brand manufactured wood
strakes. Costco sells them real cheap.
I soaked a piece of this stuff in water
for a week. No apparent difference. The
grain is actually a photograph of random
maple pieces. The photograph is
embedded in a very thin plastic ply over
the wood product (that's what Harmonics calls it).
Maybe. Maybe not.
However, Swingman put it very well. You
asked for feedback and got it. It wasn't
what you wanted to hear. And you swung
You think the Wreck is abusive? Try just
about any other group. And to tell you
the truth, calling a spade a spade is
far from abusive. Most who responded
said it was a bad idea.
Think about what you just did. You came
in here, thinking (rightly) that you
were consulting with some
professionals. And you got professional
advice. Not a single supporting post for
your idea. Even the manufacturer advises
So, you're bucking conventional wisdom,
manufacturer's specs and good common
sense and whining that people think your
idea is idiotic.
Good thing this stuff is cheap at Costco.
Good for you! That should last at least a week. Although I have been
in the construction business for almost 40 years, you are obviously more
of an expert on this stuff than I am.
Never heard of Harmonic. But then I have only installed about 150-200
thousand square feet of flooring. I obviously still have a lot to learn.
And why would you be worried about water?
Good luck on installing your floor! There is no way it will hold up with all
the flexing it will deal with because of the "cushion" of the carpet and
pad. Trust me, you are asking for certain failure!!
Moisture is far from the problems you will see. The plastic pad they sell is
there to also deal with noise transmission, not just moisture.
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