Thread: Garage Floor Clearance Issue

Since code requires a step up into the house from a garage, why do gas water heaters need to be elevated 18" as opposed to being against the floor?

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Have you ever seen the warning label on water heaters with the little fire breaking out due to the ignition at the water heater?
Flammable vapors tend to have higher concentrations along the floor and testing indicates that elevating ignition sources (not just water heaters) a minimum of 18" reduces the risk of ignition since the vapors tend to dissipate as you go up.

The CPSC estimates that about 800 residential fires are caused by gas water heater incidents related to flammable vapors each year, resulting in about five deaths and 130 injuries.

http://www.aga.org/NR/rdonlyres/58EC...ABLEVAPORS.pdf

Thanks for the response. Glad to have an answer.

Maybe I'm reading your question differently than Jim.
The 18" requirement is for units installed in the garage - not the house - unless flammable storage areas.
Most common gas/paint vapors are heavier than air and settle toward the lowest point and are therefore more susceptable to ignition sources. Thus the 18" clearance lowers the risk. Apologies if I misunderstood your question.

What code are you referring to that requires a step-up from the garage?

Actually I read it in a Dearborn book entitled "Systems and Standards, The Principles of Home Inspection" p 117, requiring a 6" step-up. Is this not true? Would certainle like to know.

Originally Posted by Darren Miller

What code are you referring to that requires a step-up from the garage?

Funny, I had the same reaction last night when I first read this but was too tired to dispute it. If there is such a requirement, it's something new because I can think of several subdivisions of newer houses where you walk straight in. Granted, it's rare and usually registers in my mind as uncommon but I've never known it to be wrong.

I do not believe there is a code requirement to step up from the garage to the house. It has been a standard practice to put a step up in case of spills etc.

It's one of those "basic construction knowledge and common sense" items not addressed by code.

Many years ago when I first started inspecting I inspected several new homes for some clients, the builder built the living space and the garage at the same level, no step up to the living space. I wrote it up and he said "prove I have to do that", I responded with "*I* don't have to prove are you are not required to do that, simple common sense knows better, after all you have to raise ignition sources up above the garage level, so why would you want those fumes to spill into the house along the floor?" - my clients were present and started reconsidering their purchase of those homes.

That was in Boca Raton in Palm Beach County, the city building official I asked looked and said there was nothing in the code which required the step up, but common sense and basic construction knowledge did.

I advised my clients that it was not the safest way to build, and that it seemed that EVERY OTHER BUILDER knew better too. Then I started looking around more closely for other reasons which my client could use to get out of their contracts and found many: The top of the slab was at garage level, not because they had raised the garage level, but because they had lowered the living level to the garage level, which put the living level too low, there was leakage all around (upon very close examination you could see it was starting to happen) and then there was the issue of the elevation not being above BFE/DFE, then, and then, and then, ...

Several of my clients got out of their contracts, a few choose to buy (the houses were in a great location) but a few years later regretted it.

The builder had built several with the flat slabs, about 6-8 of maybe 20 or so planned homes, after those first few, he started raising the living slab and putting in the step up.

Any idiot builder who wants to build the living space level with the garage slab needs to live in those houses.

Originally Posted by Stephen G Sheldon

Since code requires a step up into the house from a garage, why do gas water heaters need to be elevated 18" as opposed to being against the floor?

The original post stated "since code requires..."

As far as I know, the 2000, 2003 & 2006 IRC do NOT require a step-up from the garage to the house.

The 1999 BOCA had the following-

407.5 Door sills- The sills of all door openings between private garages and adjacent interior spaces shall be raised not less than 4 inches above the garage floor.

So, if you are using the IRC, a step-up is not REQUIRED.