Screws or 22-caliber nails

[Marianne Halevi]

So I'm back with a question about my T&G wood floor in the converte

garage. I was going to put 3/4 inch plywood down on the cement floo first, on top of a vapor barrier. How do I make sure the plywood stay down? One person says shoot 22-caliber nails, 6 or 8 per 4x8 sheet o plywood (he would lend me the gun), another says drill through th plywood into the cement and put in screws with those plastic anchors because shooting in the nails might explode the cement. I'd be totall grateful to anyone sharing their experience with this.

Mariann

-- Marianne Halevi

[russellseaton1]

If you have a ROTARY HAMMER drill, not a hammer drill, then Tapcon screws will work very well. Not the plastic anchor things you mention. Tapcon screws bite into the concrete itself and hold well enough for anything that is not subject to extreme forces. You don't have to use lots and lots of Tapcon screws to hold the plywood down since gravity will help considerably. Use the correct undersized drill bit. Something like 5/32" drill for 3/16" screws I think. Hammer drills are so slow and stop when hitting aggregate I cannot stand to use them with Tapcon screws. I hate hammer drills. For attaching electrical boxes to concrete walls, use the Tapcons with a rotary hammer drill.

The powder actuated nails work very well and are very quick. Every now and then you get blowout of the concrete. But not too often really. You minimize this occassional problem considerably by firmly pressing down on the wood being fastened to the concrete. For attaching framing to floors and walls in basements, this is the method to use. And any blowout is going to be underneath and hidden so you will never see it or even know.

[Charley]

I would use the Tapcon screws. I think it's the most reasonably priced method and it works really well. Rent a good rotary hammer drill if you don't have one, buy the specified diameter bit for the size Tapcon screw that you will be using (maybe a spare or two) and it will be an easy installation. A good standard driver/drill will easily drive the screws in once the holes have been drilled. Make sure that you drill the holes deeper than the screws are long to allow for a debris pocket under the screw.

[Lew Hodgett]

Marianne Halevi wrote: > So I'm back with a question about my T&G wood floor in the converted > garage. I was going to put 3/4 inch plywood down on the cement floor > first, on top of a vapor barrier. How do I make sure the plywood stays > down? One person says shoot 22-caliber nails, 6 or 8 per 4x8 sheet of > plywood (he would lend me the gun), another says drill through the > plywood into the cement and put in screws with those plastic anchors, > because shooting in the nails might explode the cement. I'd be totally > grateful to anyone sharing their experience with this.

I'll play the devil's advocate for a moment.

Yes, you could shoot Hilti nails, yes you could drill for concrete anchors, but WHY?

Assuming this is a typical garage of about 10 x 20, accurately fitting and installing plywood cut from 4 x 8 sheets is NBD.

(BTW, a typical sht of 3/4 ply weighs in around 60-65 lbs)

A layer of 3/4 T&G on top of the plywood will insure minimum movement of the plywood sheets relative to one another.

It will also add another 50-60 lbs/4x8 section.

On top of this construction, equipment, benches, etc, will be placed.

Assuming the floor is kept dry, nothing is going to move or warp.

BTW, I'd use adhesive rather than nails to install the T&G.

Lew

[Thom]

Some interesting ideas already expressed.... I'd be thinking of something a little different... I think framing the concrete floor with 2x4's first then plywood then tongue and groove. I would tend to leave the 2x4's floating to allow for seasonal changes. I don't know where you live but here in southern Illinois it will be hot as blazes with high humidity one day and cold as snot the next. Also by floating your 2x4's you get a chance to level up the floor so your tongue and groove will install nicely and not be as subject to peaks and valleys casued by uneven concrete.

entrance into the garage could be an interesting challenge but I'm sure could be overcome very gracefully....maybe even allow for a small ramp to roll your heavy equipment.

Just some thoughts.

good Luck. Thom

[RicodJour]

Your concrete slab is not flat. It looks flat, but it's not. Very possibly it also has a slight pitch towards the doors, or if there is a floor drain in the middle of the garage, the pitch will be towards the drain. The little 1/8" (or less) pitch per foot can wreak havoc when you're trying to put in a flat, level and stable floor.

Six or eight fasteners per sheet of plywood will keep it from sliding around and will keep the corners pinned down, but it will do nothing to keep the plywood from warping. The plywood's bottom side will be sitting on a vapor barrier in your scenario and the top side will be under the T&G - these are two very different conditions and the plywood will curl away from whichever side is the wettest or experiencing the highest humidity. Not a good situation.

A better solution would be to use a sleeper system - wood fastened or glued to the slab with construction adhesive. The sleepers should be shimmed level. If you use 2x sleepers they should be shimmed every foot or so. A plastic vapor barrier is draped over the sleepers and rigid insulation is then installed between the sleepers (you didn't say where you are located - if you're in the South you can omit the insulation). The plywood subfloor is screwed to the sleepers, building felt laid on top of the subfloor, then the T&G is installed.

As an alternative, you could use one of those easy to handle panelized subflor systems, such as Subflor. There is no need to add an additional vapor barrier or attach the panels to the slab as they're designed to be a floating floor system.

A big box store should carry them.

R

[dadiOH]

Exploding concrete isn't the problem with the powder ones. True, a smallish area may chip off at the point of impact but that doesn't effect the holding power.

The problem is that they come in different loads and you have to know the concrete density to select the proper load...too weak and they won't go in all the way and you'll have to hammer in manually; too strong and they may well go clean through the plywood. Even if you know the concrete density you'll probably find areas that are harder or softer. And 6-8 nails is not nearly enough.

Screws into plastic anchors are a lousy solution. The anchors, not the screws. Lead anchors are much better. Or tapcons as others suggested. And more than 6-8.

[B A R R Y]

I've used lots of Hilti (and generic copy) 22 ca. nails, and find that testing easily determines the proper force load. A few may still screw up, but you'll be in the ballpark.

The real issue I've seen is concrete that's too fresh and concrete with too much aggregate. The fresh stuff falls apart, and the aggregate is rocks!

[Marianne Halevi]

Wow, what a bunch of good and useful information! I thank you all s much. - Floor not level? O-oh! I never thought about that. Insulation? I was kind of trusting that I wouldn?t need that, since live in Southern Cal. - Sleepers with shims? Sounds very good, but think the level of the floor would then turn out higher than th thresholds (I already have two doors installed with red brick step outside). It seems that those Tapcon screws you talk about is what will use for the plywood (I?ll remeber the rotary hammer!) Maybe I ca use shims to make the plywood subfloor as level as possible? Maybe us glue as well to keep it down? Building felt under the T&G also sound good, and I?ll look into that too. But why use adhesive rather tha nails?

Mariann

-- Marianne Halevi

[Lew Hodgett]

The man has been to the movie.

SoCal or not, insulation is a good thing to minimize sweating problems.

BTW, what part of SoCal?

- Sleepers with shims? Sounds very good, but I

It probably will, but you work around it.

Nails are metal, metal rusts, especially in a converted garage.

Lew

[Marianne Halevi]

Aha! Rust! I guess that would go together with the sweating. The onl thing is, I am kind of paranoid about fumes. All this chemical stuf that exudes potentially toxic vapors, but I think it's worthwhile t check out where different adhesives fall in that respect.

Otherwise: Tapcon screws it will be (with lead anchors!), becaus definitely my concrete is of a rather low quality - I have already see it disintegrating in some places and had to patch it.

Gosh, I've learned such a lot. Thanks again to all! - It's L.A. area BTW, San Fernando Valley.

Mariann

-- Marianne Halevi

[dadiOH]

Tapcons don't need/use anchors of any sort...all that is needed is a hole of the correct diameter and depth.

[Lew Hodgett]

Don't sweat it.

SCAQMD has so many restrictions concerning products with VOC's that you will be lucky to find a good adhesive to do the job.

Just curious, have you ever had any flooding problems with this garage space?

Didn't happen this year, but 2"-3" of rain in 24 hours can have some interesting results.

Unlike the beach, you definitely can get some large variations in temperature in the valley. Plan on addressing insulation issues to minimize possible sweating problems.

Lew

[Father Haskell]

I'd worry a LOT more about having to redo the whole job from the ground up because of adhesive failure than fumes in the garage for 24 hours, assuming you can actually buy solvent-based glues anywhere in CA. I've had Liquid Nails water-based subfloor glue fail between concrete and pressure- treated plates (you'll want CDX ply, essentially pressure-treated subfloor plywood, in that garage) and I'll neither use nor recommend it.

As for solvents, they're tested on white mice of a certain strain in an effort to see how much is needed to make half of them sick or die. Unless you're a mouse of a susceptible strain, don't worry. Limit your exposure and crack the windows until the fumes are gone. Or pay someone else to lay the subfloor.

These, I love and do recommend. Big, coarse, cement-eating threads. No anchors needed.

What are your seismic codes? Would a floating subfloor be preferable?

[Lew Hodgett]

Liquid Nails would definitely NOT be my adhesive of choice.

Much prefer SikaFlex or even 3M, 5200.

SikaFlex is a major player in both the marine and industrial/construction adhesive markets.

Lots of industrial distributors.

Tech service has an 800#, are in Detroit, and a savvy bunch.

Lew

[Mike O.]

As someone pointed out, Tapcons don't require lead anchors or anything in the hole. If your wood floor will be directly over the plywood, the thing you may need to watch for is that the heads of the Tapcon screws end up flush with the top of the plywood. We install the Tapcons with a hex socket loaded in a drill but using this method getting the head sunk into the plywood can be a problem. You may want to counter sink the hole before installing the screw.

Mike O.

[Marianne Halevi]

Hold it ! - I am starting to be a little bit confused, almos starting to see white mice running around in circles, not fume-induce either. Maybe this is what I think I should do after absorbing all you smar people?s advice: First on the cement goes tar-paper against moisture then the plywood with the Tapcon screws (3/16 - coarse, cement-eatin threads - with a 5/32 drill bit - rotary hammer drill), no anchors No adhesive failure either. Drilling the hole a little deeper than th screw (I remember that part). Then a layer of building felt for little give (I like that idea). Then, how can I use glue for the T&G o top of that? I can?t. So I use the nails, sweat or not. The garage ha never flooded in the past 10 years that I have lived here. Earthquake Well, everything is still standing, so maybe I am o.k. (I am not i Northridge). So, do you think that is good procedure? Any concerns o objections or better ideas? As always, grateful, Marianne

-- Marianne Halevi

[Marianne Halevi]

Ah yes, and countersinking too

-- Marianne Halevi

[dadiOH]

Yeah. ___________

1. Get ply made for the purpose...it has T & G edges
2. Stagger the ply joints.

[Marianne Halevi]

again a million.

Marianne

(Hail to early risers!

-- Marianne Halevi