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Garage floor of wood - building permit problem

I want to build a post and beam 2 car garage with a wood plank floor. This will be better for the cars than concrete - will avoid the moisture from when concrete sweats like a beer on a hot humid day. The state building code in NY and most other states requires a noncombustible surface. Does anyone know how to convince the permit officer that wood is ok, or does anyone have a good alternative material?

Forget about trying to convince the building inspectors…if build code says wood is NOT ok then I don’t use wood.

Alternative…How about this…

Dirt! No really, I can see why they want a non-combustible material. When I was a kid, the first house we moved into had a garage with a wood floor. One night it caught fire. And with the years of gas and oil absorbed into the wood the thing went up like a match box full of matches. Dad’s Jeep burned up in the garage. The fire was so hot that the headlights melted and the Jeep’s frame was a twisted mass of steel. The only things we found after the fire besides the Jeep were an asortment of hammer, axe, shovel, etc…heads. Nothing else was left.

Go with concrete.


Go with concrete. Your reasons for shunning concrete are lightweight indeed. So concrete can sweat? Where do you think the water comes from? It comes from humid air and your car is exposed to this same air regardless of the floor material. Run a controlled experiment for twenty years and you will see the cars’ conditions are not affected by the floor.

Why don’t you use either a flooring cover like MikeInNH suggested or have the concrete floor coated with one of the epoxy sealants? Wood floored garage = fire.

The last house I had had a attached garage with a concrete floor.

After hearing about numerous house fires that start in vehicles parked in garages I took the advice of a fire prevention officer (my son), and installed a sprinkler system.

It cost very little for the extra peace of mind.

epoxy sealants?


I cannot think of a better fire than one fed with oil and gas soaked wood. Don’t do this.

As someone else said, building materials don’t sweat. Only living things sweat. So called “sweat” on nonliving surfaces is actually moisture from the air deposited on the cooler surfaces.

If you really want a nice floor, there are tiles and decorative surfaces that you can put over the concrete. Just remember that some of these can be real slippery when wet, so be careful on your choice.

“will avoid the moisture from when concrete sweats like a beer on a hot humid day”

Where do you live?

In NJ, where I live, the summer humidity can get pretty brutal, yet I have never had any instance of the concrete floor in my garage “sweating”. My garage floor is always dry, except after I drive into the garage when the car is wet from the rain.

If your garage floors in the past had a “sweating” problem, I think that the builder failed to put in any kind of moisture barrier. And, I agree with Mike in that this is not something that is discretionary for the building inspector. The building code is the building code, with no wiggle room.

Well not only are they right about the fire hazard, think oil soaked wood, but it is not going to reduce the humidity. Likely the “sweat” you see on the floor is from the air as the concrete is going to be cooler than the air. In that case it is making the air less humid by removing that moisture from the air just like a dehumidifier.

You can put a few coats of a masonary sealer on the concrete. If you keep the garage closed during the summer,
you can use an on demand dehumidifier and have the moisture it removes go down a floor drain.

aside from the comments about the moisture is already IN the garage, and the cold concrete is letting it condense being true, there are alternatives.

how much do you want to spend?

they make prestressed concrete panels you can use on the floor. they span around 9.5 ft. so they willmake a garage floor nicely. this is assuming you are thinking a second floor garage.

if it is a first floor garage i think it is pretty hard to beat concrete. both for safety and economy.

on second thought, if you are thinking of the first floor being wood plank, think how the joists underneath are going to rot out in 15 0r 20 years! no PT or vapor barrier is perfect, and in close proximity to the dirt it will be wet always.

N.Y.–hot & humid summers. Cold and humid winters. Go with a concrete floor. After the concrete is set properly, use an epoxy concrete coating/sealer. A manufacturer or two offer non-slip coatings. Google, Yahoo!, or etc., “Garage floor coatings” or “concrete floor coatings”. You can also try,, or any number of other search engines.
The coating will not allow petroleum products or fuel to sink in and will greatly reduce the “sweating” that you’re concerned with. A dirt floor, on the other hand, will absorb these petro products. What if some dumb-a$$ shows up and decides to chuck a lit cigarette or cigar onto that petro-soaked dirt floor? How about that hot oxy-acetylene torch or etc.? Just food for thought.
Have floor drains installed with the pitch towards the center of each bay. You can probably get away with 3" PVC DWV (polyvinyl chloride/ drain, waste and vent) piped to the outside of your building. The usual way is the concrete contractors pitch the whole slab towards the doors. Surer than he77, that melted snow and ice from your vehicle will run towards the door(s) and freeze. Uh-oh! My door is frozen shut! That might tear off the weather proofing gasketing on the bottom of the door and could possibly offer enough resistance to lifting that it burns up an electric door opener. A little pre-planning will help you greatly in the long run.

“N.Y.–hot & humid summers. Cold and humid winters.”

Only on the costal plain. In the central and North parts of state the weather is much nicer.

For the OP’s problem, appropriate climate control is the partial answer. You want to ventilate when it is dry outside and seal the garage up when temperature of the slab is below the dew point.

This comment-

when concrete sweats like a beer on a hot humid day

is leading some to say that condensate is the only means for floor moisture to occur. That just isn’t true. Unfortunately, I know that first hand.

Concrete will pass moisture and there is a critical test that should be done before finishing basements with concrete floors where the right conditions exist. If there is high moisture in the soil for any reason, you can get it coming up through the concrete. The test involves taping a sheet of plastic to the floor so that all edges are sealed. It’s left overnight and checked the next day for the presence of moisture trapped under the plastic.

I had a garage slab and basement floor that passed moisture in this way and I had to install a special underlayment prior to finishing the basement floor. The garage almost always had a humid atmosphere except on those days where the low relative humidity outside allowed the moisture to fully dissipate.

I think you need to look into fireproof coatings. I love wood floor garages(aka barns).

Happy fishing:

This is nut.

First of all, it would take a heap of convincing to me that a car sitting on concrete is any sort of problem at all. If I had a car that couldn’t sit on concrete without damaging itself, I believe I need another car.

Second, It would take lumber that they don’t sell anymore to make a wood joisted floor strong enough to hold what’s sitting in my garage. I believe my tool box would go slap through a wood floor.

Third, if you’ve got a moisture problem, it’s not going to get any better with wood. In fact it’s going to be a lot worse as the wood will deteriorate faster resulting in you one day having to ask, “How do I jack my car up that fell through my wood floored garage and is now sitting on the floor joists.”


If you go to a real mill yard you can get joists from barns as salvage or even milled new to create this type of structure. Remember people still create barns and animals have a significantly larger point load(one foot) than a vehicle tire does.

Still won’t pass inspection.

For the most part, barns either have a dirt floor, gravel floor, or cement. I don’t ever recall seeing a wood floored livestock barn. The termites and rodents would make quick work out of such a thing.