Here is a question that my father and I where pondering the other day and we really could not find a justifiable answer to the issue. The question was with the price of urethane glue and possibly MVP for a glue down installation and the price of cork and poly for a floating installation vs. the price of poly / plywood / roofing paper, why would you recommend any other installation?

I really though about it and at around $300 per 200sq ft. For glue and MVP it becomes a huge additional cost, even glue alone will run the customer $150 and even if you vend the product margins are slim on it, so there is no great incentive to sell it. I broke it down to .75 to 1.50 per sq. ft. to add glue.

Floating really does not get any better at nearly $150 for 200 sq. ft. it weighs in at right around $0.75 per sq ft as well. Adding poly which is around $20 for 200 sq ft brings it up to $0.85.

Conversely if we look at installing a wood sub-floor. The plywood is around $18 for 32 sq ft. or 1 sheet this equates to $0.56 adding poly brings it to $0.66 and felt paper brings it to right at $0.70.

Granted there is more labor cost involved with laying a sub-floor, but it strikes me as peculiar that what I consider to be the most stable, secure and authentic flooring installation comes in 5 cents cheaper than floating install. Further with most engineered manufacturers now recommending the use of the LHF gun to do staple installs on their products, I can’t really see any advantages to do a glue down install. If you incorporate MVP the cost will actually come out higher for the total install given the cost difference in the instillation methods. I still see the cost benefits in floating installs due to the reduced labor costs, but I feel that it is an inferior installation method to glue or staple. To me it seems that glue is pretty much obsolete. Someone else may have a different perspective, but I cannot see a valid reason to recommend a glue install, other than a client insisting that they do not want the height profile.

IMO, that is the major difference, the height issue. Since many concrete slab homes were built with thin floor coverings in mind (carpet, vinyl, ceramic tile) to raise things up 1" to 1&1/2" causes multiple problems with exterior thresholds, appliances, cabinetry and doors. But I agree that a nailed down floor over plywood is a much nicer floor to walk on. I don't think I agree with your numbers though. Here, 3/4" CDX is more like $25.00 a sheet and I never have felt nailing the plywood down only was sufficient. I always glue and nail, and since I'm full spread gluing, the cost goes way up because of that. I suppose one could use a cold bond mastic where available but often it isn't and it is slow curing and drying. So for moisture control, I prefer to use a low cost sheet vinyl glued to the slab with the plywood glued and nailed to that. Then install your wood flooring over that. This works when the customer wants a 3/4" solid finished in place and they're on concrete. But in reality, you could skip the plywood and glue down a quality engineered and it would cost less, not more. And would take less time. The MVP is expensive and I think that Bostick's looked at what they could charge and get away with rather than what the product actually cost them to make and market. Hopefully, other manufacturer's will jump on the band wagon and the competition will force the price lower. Taylor and Franklin already have. I still think a floater is your least costly. You can get a roll of 6 mil poly film for $.33 a ft and your Volara foam for around $.30 a ft. Or use the 2in1 or 3in1 foam for even greater savings. Gluing directly to concrete with Bostick's will cost about $.60 a ft. If you add the MVP you can add about anothr $.75 to that number for a total of approx. $1.35 a ft. for moisture control and adhesive. Gluing down cheap vinyl as moisture control costs similar to MVP; less money for material (.$50 a ft. ) but more labor whereas MVP is more money for material but less labor. Anyway, that's how I see it.

Yikes, $25 a sheet must be those impact fees in Cali. I can get ¾ here in FL for about $18 a sheet but $25 would defiantly change my numbers. As well, I think you are getting Bostik products at a better rate than I am able to here. I nail to the slab with a powder load and it has worked well for me, I shoot about 1 nail per sq ft. We have a grid system that we use where we nail in the cross sections of the grid. As well we apply asphalt tar from a caulk gun and shoot through the asphalt tar to seal the hole, it holds really well and save a lot of time and money over spreading cut-back or glue. Once down the plywood has to be busted out to remove it. I did not include foam or 3in1 because we do not use it. If we float a floor, we only use cork and a moisture barrier. We tend to shy away from floating installs, but yes I guess you have a point that 3in1 can save a boat load over installing a sub-floor. Even with cork floating comes out cheaper when you factor in labor but my main revelation was that it seemed to me that glue was more expensive when you factor in materials and labor. I know I charge quite a bit more for glue installs than I do for a nail down.

For the sake of argument, let's say you (or any installer/contractor) charges a $1.00 per ft. more to glue a wood floor down over nailing one down. So on that 500 ft job, it's $500.00 more in labor right of the bat, not to mention the $1.35 for MVP and BEST. So now you're $2.35 over nailing but to nail you need a subfloor. Even with your system of installing ply, when you factor the materials (plywood, asphalt tar stuff, powder activated fasteners,etc.) and the labor, that plywood subfloor is got to cost about the same or more. As I see it, from a cost point of view, it's a wash.

That is the conclusion that we came to, as well. I know that it is just me, and there is probably someone out there that is the exact opposite, but I can lay a sub-floor almost twice as fast as I can glue. We make more money from glue installs but if we factor in time we make about the same per days work. Sub-floors and stapling allow us to schedule more jobs and quite frankly I prefer the work of a nail down install, I hate cleaning glue off of the boards and worse yet myself. After pondering the subject for a while the only advantage that I could find for glue installations was height issues but we have developed a lot of workarounds to overcome those issues. Other than height profile what can you see that is a clear advantage for glue installations?

The ONLY advantage I can see is IF you use a manufacturer's moisture barrier (like MVP) and their adhesive, you get a warranty of sorts (good luck getting them to stand behind it). With the plywood over slab install method, you, the contractor, are the warranty. So you lessen your liability with a direct gluedown. Also, after 25 yrs in the biz, I've seen plenty of plywood over concrete subfloors fail. They were probably done wrong but with a more complex system, there is more to go wrong. The advantage of plywood over concrete as opposed to direct glue down is no annoying hollow spots and popping sounds, unless one does a poor job of attaching the plywood. PLUS, as you mentioned, glue removal. My least favorite job is scrubbing/cleaning urethane adhesive from a glued down floor.

I have become pretty good at keeping glue off the face of the boards. I keep a rag with minerals spirits on it close by at all times. I'm constantly wiping my fingers with it, and anything smudged on the floor. I have got in the habit of palming the board to keep my fingers away from the glue.

Thick wide plank, I can keep clean as a whistle, without having to wipe anything up or off. But the ¼", 2¼ is a challenge to keep clean.