In your May/June issue you showed gluing down 1/4 inch underlay in order to avoid telescoping of joints and fasteners through the finished vinyl flooring. That is well and good, except that the wood parquet adhesive you recommend will cause staining of the vinyl, and your customers will be even more unsatisfied.
Good Point. The On-Site Innovation series comes from construction tips that were published by the CMHC and sometimes solving one problem can cause another that is not obvious at first sight. So we ran this tip by associations and manufacturers and got more than we expected, both supporting and opposing this "working tip". We have asked Jon Eakes to give us a complete picture on vinyl underlays.
It seems that we have all had problems with resilient floor coverings at one point or another so it is interesting to see that large flooring companies like Congoleum have put together very detailed professional installation guides that include all the underlay problems. They are careful to state that they are offering recommendations only and that problems caused by underlayments are not their problem.
I don't want to reproduce pages of information, but here are some of the recommendations that are often poorly understood. There are basically two objectives trying to be met here: avoid dimensional changes that can cause telescoping; and avoid staining caused by chemical migration from below.
Double-layer floor construction a minimum of 1" thick.
Stager all joints in flooring panels.
Provide 18" of well-ventilated air space below joists when close to the ground. Note that this precludes vinyl on a plywood floor over slab on grade or basement floors, even with sleepers. Proceed only if you know you have found your own way to prevent dimensional changes in the panels due to moisture.
Minimal thickness for underlayment panels is 1/4 inch. Although Lauan can be thinner, more and more Lauan is showing staining problems.
Here is an interesting one -- fasteners for underlayment should not penetrate any framing such as joists, but only nail to the subfloor.
Any adhesives used to install underlayments must be known to not stain resilient floor coverings. Yes solvents can go right through 1/4 underlayments. If you are gluing anything below the underlay, use high-quality, nonstaining, solvent-free, construction-grade adhesive, or light-colored PVA woodworking-type adhesive. This definitely precludes using standard parquet adhesives but opens up to polyurethanes like PL Premium.
The list of what else can cause stains is impressive: edge sealers, patching materials, marking inks, solvents, adhesives, dyes, paints, surface voids filled with factory-applied synthetic patching compounds, pieces of bark or other wood chips, or strands that will stain which may, or may not, be readily visible!
With all that said, there are actually some panels that fit the bill and they are mostly indicated with a clear "APA Underlayment" notation, which means you want a stamp assuring you that you have the right stuff.
Just to clarify, here is the NOT-RECOMMENDED list:
-- Chipboard, Waferboard, OSB (except for some specialized underlayment products), Tempered hardboard, most Particleboard, and Wood Veneer and other composition panels not recommended for underlayment use such as treated and fire-retardant plywood.
**Originally published as an article by Jon Eakes in Home Builder Magazine, the magazine of the Canadian Home Builder's Association.