Pouring Concrete and Shooting Nails

28 days.

Well I suppose you could shoot nails into still fresh concrete if you like. 28 days is the industry standard for concrete cure time for testing purposes. Have you looked up building codes for your area?

RVZ has it right about the 28 days 'till optimal set has occurred. It's OK to shoot into REALLY fresh concrete, when the forms are still in place and the mix can still be worked. Just make sure to rap the plate to settle the aggregate. Too soon after initial hardening you run the risk of disrupting the weak chemical bonding that needs to finish. You'll wind up with an area of weakened concrete around the nail. After 28 days the bond will be strong enough to resist the shock. I advise using pressure treated lumber for any pieces in contact with the concrete, especially below grade.

I think you could do it safely in a couple of days, but to be conservative, wait for seven days.

What #3 said, and a GA to him.

Actually, "no intention of stepping on anyone elses' post," concrete lugs are generally broken/compression tested at 7 days for the first test. If they have reached the required strength, no further testing is generally required. However the standard requires the concrete to reach specified strength generally at 28 days, and again will be tested if it did not reach the specified strength, at the 7 day test. The next break specification is at 52 days, and if the concrete has not reached the specified strength by 52 days, there will be financial sanctions against the provider or contractor.

If said concrete as is placed is expected to have a reasonable lifespan for 20 years, this is based on the mix as specified by the engineer, on behalf of the owner. The owner may determine that it is in his best interest to accept said concrete now as replacing it will delay his grand opening or something like that. So the engineering standards will be used to estimate the projected usful life of the concrete that was late reaching the prescribed strength. Maybe the standard will determine that this particular designed mix can only be expected to last for 10 years before replacment.

Should this occur, the owner is entitled to a substantial reduction in the cost of that concrete, and the labor to place and finish it, as he can expect to have to pay to remove and replace said concrete again at 10 years.

As for the answer to your question, nailing should be ok after 7 days, but not near the edges. In todays construction world, the use of "tapcons" is generally a better way to go. Simply drill a hole in this fresh concrete and incert the screw through the pressure treated bottom plate. "Tapcons" is a registered trade name for a brand of screw that is designed to be screwed directly into concrete varieties. I hope this answers your question and provides knowledge for any future projects you undertake to perform as a do it yourself endeavor.

TooMuchFun

I am in agreement with TMF, having often done this. Specifically what you do is use a hammerdrill to drill through the plate, into the concrete, and then screw in the tapcon.

Actually I would not recommend using "nails", to attach the bottom wall plate to the concrete, tapcons are the way to go.

As was mentioned in the thread, you should definitely use pressure treated wood. Nailing the SPF studs for the walls to the pressure treated wood, calls for ACQ nails now, though you could use ceramic coated screws instead.

Transcendian,

Do you think the pressure treated wood should be separated from the concrete by a layer of 6 mil polythene? Our building inspectors seem to call for that consistently, but I am not sure that it's necessary.

can't see how that is of particular hurt, but also don't see it of particular benefit.

Of course you have to do what the inspectors tell you to do, though they get on jags that can over time be proven to be stupid.

For instance plastic sheeting was long demanded, but proved to trap moisture and degrade the overall integrity of the structure.

About the best uses of plastic sheeting I know of are as a layer between compacted gravel, and the concrete.

I have also used it on greenhouse frames, but told people that the plastic will degrade in sunlight within a couple or few years, at the best.

Hi,

Plenty of good advice about the method of fixing. I've found that green concrete is not one of the best media to get reliable fixings into; but trial and error will suffice.

My comment will be about the suitability of an unventilated void between the face of the concrete and the finished surface,plaster board? The suggestion of a vapour barrier is a step in the right direction also the application of a 'tanking compound', to seal the surface, (before fixing the battens,this especially important if there is any chance of moisture migration from the surrounding soil, as a build-up of dampness behind the scenes is guaranteed to cause problems (even dry rot etc) in time.

Be aware also that the concrete surface will be cold in relation to the internal space and being a bathroom you will no doubt have a shower etc. Again any tendency for this humidity to gain access to the wall is a potential trouble spot. Therefore pay attention to sealing the finishes properly to avoid this problem, A good extract system helps!

Its always a good idea to allow the concrete to cure for at least 7 days before loading the slab, you can nail down your plates 3 days after placement though. I prefer to drill through my plates into the concrete at least 3" with a 3/16" masonry bit and then double (2) - 16 cc framing nails at 24" on center. By drilling you will be less likely to POP the concrete from either nailing or shooting down your anchors.

Good Luck

Mark

yupe2be@hotmail.com