Floor underlayment questions

I have a kitchen floor that is on a concrete slab. Above the slab is old asbestos tile, and above that is a vinyl sheet floor. Now that hardwood has been installed around the kitchen, I want to bring up the level of the kitchen floor to at/near the hardwood (about 1/2" higher), and put down new vinyl too. I plan on putting down 3/8" underlay- ment, then vinyl, then some threshold molding to join it with the hardwood.
Questions:
1. What type of material should I use for the underlayment?
2. What fasteners should I use to anchor it through the vinyl, asbestos, and into the concrete?
3. How much space should I leave at the seams between sheets?
4. How much space should I leave at the wall edges?
Thanks, Joe
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Plywood. (NOT any kind of OSB, chipboard, or particlae board.) Get the best that plywood you can afford, so far as surface quality is concerned. At a minimum, you should be getting "B/C sanded one side". A/C is even better.

There's lots of things that you could use. I'd probably opt for Tapcon screws. The biggest problem that you will have is that you MUST countersink the heads of whatever you use -- but you got to do that without drilling the countersink all the way through the ply.
Make sure you cover the countersunk screwheads/nailheads with a hardening putty or floor-leveling compound.

Absolutely none. In fact, if you can find a tongue and groov plywood in that thickness/grade, go for it. After all of the ply is in place, you'll need to "mud" the seams with a floor-leveling compound. For vinyl flooring, it is rather important that there be NO voids in the substrate.

Plywood doesn't move very much at all -- that's one of its big advantages. leave about 1/4 inch, just so that you can work with the edges some.
DT
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
"YesMaam27577" wrote ...

Thanks very much for the help. I have one more question:
How far apart should I put the screws?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
YesMaam27577 wrote:

That's complete nonsense. professional installers nationwide use particle-board underlayment for vinyl..
IMHO the rest of your advice is moot. With the real possibility of sheet underlayments of any kind coming loose when installed over a slab it's best not to do so in the first place and use transitions to deal with the elevational differences.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
"the_plumber" wrote ...

OK, if I take your advice, can I put the new vinyl over the old vinyl without pulling it up first? It is glued 100%, not just the edges.
If I can put it over the top, what adhesive should I use that will fill in the slight pattern (very shallow indentations in the design)?
Thanks.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Jorabi wrote:

You prep it with an embossing leveler first. Then use vinyl adhesive. Lotsa info on google about embossing leveler.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.