Basement under garage, Part II

[Zone_V]

First of all, thanks to everyone who took time to give their input.
All the responses got me thinking (uh-oh) that if it's not an essential idea to slope the floor to a drain....would the floor necessarily have to be concrete? Keep in mind this is a one-car garage, probably sixteen foot wide span. How about just using the appropriate sized laminated veneer lumber beams or engineered wood "I-beams", covering these with glued and nailed 3/4" t&g plywood, and then some sort of water-resistant flooring material, such as vinyl? When the vinyl started to deteriorate from road salt, water, wear, etc, just replace it.
Your ideas on this possibillity would be much appreciated!
John

 

[Bob_Skurka]

Engineered lumber is capable of taking amazing loads, but I think you will find that a simple layer of 3/4" t&g plywood flooring won't be up to the task. Maybe if you double up the plywood and make sure the seams are staggered. A structural engineer needs to take a look at that issue. Plywood is capable of deflecting loads and has some amazing shear strenght to weight ratios, but we are talking about a vehicle that weighs several thousand pounds resting on 4 tires, each of which will have a contact surface area of perhaps 7" by 4" and so each of those little 7" by 4" areas will be holding roughly 1000# of weight (assuming 50-50 weight distribution of the car which is actually highly unlikely so it is reasonable to assume that 2 wheels will hold 800# while 2 will support 1200 for our theoretical car).

The plywood might be rated to hold 1200#, but what you will have to deal with, in the case of the plywood floor is that it will have to support that load over a couple of decades and with humidity changes. I suspect you will very quickly develop 4 low spots.

You will probably be looking at placing the engineered lumber below the floor on 12" centers as well.

This is not insurmountable. It is an engineering issue. Also, I like the idea of the sheet vinyl floor, but I would make sure that it was seamless so there was no place for water to seep down to the plywood. You might want to pony up the added cost of using "marine grade" plywood as the epoxies used on marine grade are more resistant to water and humidity.

 

[Junkman]

Garages must be fireproofed.... all exposed lumber must be covered with non combustable material... this all applies if the garage is in or attached to the home. If it is unattached, then it doesn't have to meet this requirement. Since a lot of people here want to fight over generalized statements, check with your building department to assertain the specifics of the code in the jurisdiction that you are building. There might just be a couple that don't follow the NFPA codes and allow unsafe building practices.. /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif

 

[Inspector507]

Our local building code only requires that the portion that connects to the house be covered with ½" gypsum (drywall). The rest of the garage can be exposed.
BTW, ½" gysum is not fire rated.

 

[Bob_Skurka]

Our code requires the common wall(s) be covered with fire code approved drywall on any connected garage.

 

[jim_wilson]

This is very possible. Look at the Weyerhauser site for the TrusJoist products. They have tables detailing the load carrying capabilities of the different types of I Joists they manufacture. A properly designed floor would more than support even a heavy car. Think about how much a bunch of people standing in the same area as a car or a heavy waterbed is going to weigh and a car is right in there at the same weight. Instead of using plywood I would use Advantech - it is semi waterproof and they make it in a 1 1/8 thick version that would probably work better for a garage floor. Also keep in mind that you could still pour a concrete floor over this setup - it is very common to do this in cases where people install the radiant floor heating setups.

 

[Junkman]

water beds don't put much of a load on a floor, because the load is spread out over a large area. Most floors are designed for a load minimum of 60 pounds per square foot.

 

[boustany]

The problem would not be the loading (which can be engineered around) but other safety related issues such as (noted by Junkman) fire (drywall may be ok - provided there are no other paths for the fire), oil/gas/exhaust leaks, and so forth.

Remember a car is a heavy thing full of all kinds of * very * flamable and/or toxic chemicals and bits. Ever seen a tire burn? /forums/images/graemlins/shocked.gif

I doubt if you could get a wood floor garage past any building inspector, let alon insurance company.

 

[Dave___in___CT]

Hi...


Using all rough sawn lumber may fit the bill too...

Plenty of barns with wooden support beams and flooring with tractor's in 'em...


Dave...

 

[boustany]

The tricky bit is that this is a house, not a barn, residential building codes tend to protect peoplem, and are picky about these things.