Shop floor slope code

[mdbuilder]

I've been involved in code development since 1987, both NFPA and ICC, and the legacy codes prior to ICC. I'm on 4 committees responsible for 6 model codes or standards now. The substantiation of the change proposals and action on them is extensive and published and free. There's no mystery or secrecy to the model codes in this country.

I did Google "garage explosions" and looked at a dozen and find no support for fumes and slope. Fireworks, EV batteries, and shop work. Mostly no cause cited.

Garage floors use to have to be 4 or more inches below the house floor for both liquids and gases, but that went away. Cars use to routinely leak fluids, but that is no longer the case.

Plus how does slope to a drain alleviate explosion risk?

We will have to agree to disagree on this.

 

[mdbuilder]

Bill, I happened across this post of yours in investigating the code for a challenge I currently have where we are doing an elevated slab and the engineer does not want to add the dead load of a 3.5” rise (@ 1/8, 7” at 1/4).

In case you are on one of those committees and can influence the future code my opinion as builder is this requirement needs to go away as it serves no purpose in modern times.

a. Cars don’t leak anymore

b. My garages, as is becoming increasingly typical, have door seals so tight that not much would move past them anyway.

IMO while I generally prefer passive approaches that don’t fail, in this case the life safety should focus on burn time until evacuation and sensors to sound the alarm early (which are so cheap there is no good reason not to have them).

regards,

Marc

 

[wssix99]

a. Cars don’t leak anymore

Are you saying this because cars are going electric or because you haven't owned a car with Chinese parts in it?

 

[billconner]

md - I think we agree but alas I'm not involved with the residential codes. And since that post I've realized it's become a little more difficult for a person on their own to make a code change no matter how simple and innocuous. And I'm older and beginning to feel it.

 

[duneslider]

Bill, I happened across this post of yours in investigating the code for a challenge I currently have where we are doing an elevated slab and the engineer does not want to add the dead load of a 3.5” rise (@ 1/8, 7” at 1/4).

In case you are on one of those committees and can influence the future code my opinion as builder is this requirement needs to go away as it serves no purpose in modern times.

a. Cars don’t leak anymore

b. My garages, as is becoming increasingly typical, have door seals so tight that not much would move past them anyway.

IMO while I generally prefer passive approaches that don’t fail, in this case the life safety should focus on burn time until evacuation and sensors to sound the alarm early (which are so cheap there is no good reason not to have them).

regards,

Marc

This isn't because cars leak...this is because people drive cars that come in out of the weather. If your car comes into the garage with a couple inches of snow and slush what happens to all that moisture in your flat garage with tight door seals?

In my sloped garage it all rolls down towards the garage door. My door is fairly well sealed so it pools there until I open the door and squeegee it out. I wish I had a trench drain right at the door to catch it all even if I had to **** it out occasionally.

Any talk of fumes rolling out at 1/8-1/4" slope is silly.

 

[LopezBart]

In CA where we enjoyed mild weather 99% of the time, foundation-style vents screened w/ 1/4" hardware cloth are commonplace just above the garage sill.

 

[nadogail]

When I built my 24x24 detached garage I had no issues making the floor level. I knew I was going to be building a couple of race cars and wanted it level. Not even sure if they asked me anything about it. Just say its a workshop and go with it.

My 22x22 attached garage has the floor sloped and it is annoying. Its about 3 inches from front to back which means when I built a workbench along one wall I had to cut all of the supports different lengths. And yes the cars will move if you have them in neutral with the parking brake off. I deal with it on the attached garage but there is no way I would have a "workshop" with a sloped floor. If you are woodworking and want to build a cabinet you cant just do it on the floor. Etc etc etc

I leveled my Workbench, Garage Refrigerator and Cabinets to compensate for the pitch of the floor slab. Because the car drips from the AC or rain, the floor slopes to the big door.

 

[bb29510]

that only apply for parking of running vehicle, not projects

 

[billconner]

that only apply for parking of running vehicle, not projects

iirc it applies to garages in the irc. You might call it a shop but I think most building officials would say it's a garage.

 

[racecougar]

a. Cars don’t leak anymore

By what sorcery do cars no longer leak? If you have some of said sorcery, please come visit my shop and apply it to the vehicles there.

 

[billconner]

Here is 2021 IRC

SECTION R309
GARAGES AND CARPORTS​

R309.1 Floor surface.​

Garage floor surfaces shall be of approved noncombustible material.
The area of floor used for parking of automobiles or other vehicles shall be sloped to facilitate the movement of liquids to a drain or toward the main vehicle entry doorway.

I think most would interpret this to mean if you can pull a car into it and park it there, it's sloped - either to the door or a drain. There may be local amendments or interpretations that modify this. Here, for whatever reason, does not apply to detached buildings.

It does in my mind go beyond intended purpose of the code. I think today it's reasonably safe to not be sloped.

R101.3 Purpose.​

The purpose of this code is to establish minimum requirements to provide a reasonable level of safety, health and general welfare through affordability, structural strength, means of egress, stability, sanitation, light and ventilation, energy conservation and safety to life and property from fire and other hazards and to provide a reasonable level of safety to fire fighters and emergency responders during emergency operations.

 

[larry4406]

Bill, I happened across this post of yours in investigating the code for a challenge I currently have where we are doing an elevated slab and the engineer does not want to add the dead load of a 3.5” rise (@ 1/8, 7” at 1/4).

In case you are on one of those committees and can influence the future code my opinion as builder is this requirement needs to go away as it serves no purpose in modern times.

a. Cars don’t leak anymore

b. My garages, as is becoming increasingly typical, have door seals so tight that not much would move past them anyway.

IMO while I generally prefer passive approaches that don’t fail, in this case the life safety should focus on burn time until evacuation and sensors to sound the alarm early (which are so cheap there is no good reason not to have them).

regards,

Marc

I managed construction of a home with 2 elevated garage slabs (rooms below). Our engineer also didn't want to accommodate the added dead load from concrete to make the slab pitched. Instead, our steel was pitched toward the garage door such that the slab was poured at constant thickness yet it was pitched toward the door.