Preparing for h/w flooring : had a brainwave...

[radhak]

I wanna lay my floating hardwood flooring this weekend.

Today, after I ripped out the carpet and swept the floor, the concrete floor looks decently level and plane, but for splotches of dried up mortar here-and-there. Obviously whoever laid the floor was in a hurry or generally messy : they could have easily cleaned up rightaway, but because they were to lay a carpet they did not bother .

Anyway, I was able to use a throwaway chisel to knock most of the worst spots, but not all. So even while the floor is pretty much good, there are a handful of areas that could pose a problem.

So, my questions :
(a) The instructions with the hardwood (trafficmaster engineered hardwood) says the floor should be "smooth/flat within 1/8" in a 6' span". How do I measure this? If I lay a straight edge on the floor, I should not see any 'daylight' under it higher than 1/8", right? Or is there more to it?

(b) For underlayment I got the 3-in-1 Quiet-Walk. But what if I also re-use the foam that I found under the old carpet? IOW, lay the foam on the concrete, then lay the QuietWalk, and finally the wood? It would even out some of the unevenness better than if I use just the QW, I am guessing.

[Greg.B]

I don't think there is anything wrong with you laying down the foam. One thing to consider the moisture barrier. Since you have a 3-1 should that go down first to pervent any moisture come up ?

It would help a lot where there are unlevel spots. I did my basement as well, and only used the 3-1 and there is a spot I know about now, that has some give to it, becuase there must be a small "gull" in the concrete.

[mschrank]

I think you're on the right track as far as checking flatness.

But I'm not so sure about laying down the old pad under the 3-in-1 and the wood. I'm not familiar with the flooring you're using....how does it attach to adjacent planks? If it's a "clic" type system, I'd worry about too much flexing at the joints with all that padding under there.

Don't know for sure, just my .02 to think about.

[jhart]

An ice chopper is a great tool to clean up the motar spots on the floor, but it may not be something you would readily have in Florida.
I would not use the old carpet foam. Most of the floating floors have a prescribed amount of padding that should be used.
I would lay out some plastic over the concrete first, then the padding anf then the flooring. You are on the right track as far as using a straight edge to see how level it is. For low spots, more than the 1/8th inch, you need to fill in or you will feel it give some as you walk on that spot. I've used a product called "water putty" that's easy to use to fill in spots.

[dkerfoot]

I'd use a grinder for anything that won't come off with a chisel. Lumps are worse than divots because the whole board will "teeter".

I would not use the foam for the reasons mentioned.

There are several concrete fill products for evening out the floor. I'd try to resist the temptation to lay the floor until you have it right. A spongy feeling wood floor will haunt you.

[Alex Franke]

For our recent bamboo-over-concrete installation (posted on this thread), we spent the whole first day just preparing the concrete. It seemed to take forever because there was so much gunk on the floor. No mortar, though, fortunately. We were able to get everything up with with painters tools and wire brushes with scrapers. We used the flat back of a broom and shopvac hose attachment to check for high spots - you could feel if there was a high spot when running the flat edge across the floor.

[Jan]

The carpet foam will let the floor flex enough to break the tongues off the floor boards.

[Alex from Sac.]

Some people use 3 tab roofing shingles to leve lout underneathe floating floors. Try the DIY channel website at diynet.com for installation tips and help. Carpet foam is definitely not a good idea under hardwood.

[radhak]

Thanks everybody for your comments and advice. I managed to complete the floor installation during the weekend (and spilled over to Monday). and yes, the foam would have proved to be difficult to manage - ended up using just the QuietWalk.

I did have various problems with the floor, but ultimately conquered them all. Mid-way thru I found this nice little hill in the middle of the room that had evaded my inspection before ('decently level and plane' - ha!). Had to resort to emergency repair - could not find the water putty that Joe (hart) recommended, but a readymade mortar mix was useful.

I shall post pictures a bit later.