Level slab?

[no704]

I’m fixing to stand up a new garage/workshop. Will be around 30x35. Have a two post lift. Mostly storage and long term car projects. In Tempe AZ so no real rain or snow. Will most likely have some machine tools in it. Lathe, Bridgeport.
Should I get the slab poured flat level, or have a garage slope on it.
This will be a detached structure.
Also, pros, cons of going with a “flat” roof?

 

[KenC]

I vote for level. Slope is only for water drainage. You won't be bringing snow/mud/salt etc into a Tempe garage!

And unlikely to be using a hose around machine tools or unpainted projects.

Said machine tools and your lift will install much easier on a level base.

 

[billconner]

Agree with KenC on slab.

On roof, appearance would be a priority for me - flat roofs dont belong in some places. But practically, a nearly flat roof - 1:48 minimum - doesn't bother me.

 

[TractorJeff]

My floor is flat, snow sometimes makes me wish it sloped. Rubber squeegee takes care of it, plus no sand plugged drain lines

 

[larry_g]

Be a bit careful with what you call your building. I was warned off building a 'garage' because it may require a sloped floor. A 'barn' or a storage shed will not. Also be aware that level does not mean flat. When you contract the flooring contractor you have to specify the flatness your require. When I was working the buildings that we put our equipment were spec'ed at less than 1/8" variance in any ten feet. Don't be like so many on here that complain of Bird baths in their floors.

lg
no neat sig line

 

[wssix99]

Should I get the slab poured flat level, or have a garage slope on it.

Check your local codes. Sloped floors are required by code to mitigate explosion hazards. Gasoline vapor is heavier than air and the sloped floor evacuates any fumes out of the building. (Those vapors can linger in a flat floor room.) "Gas curbs" are also required for attached garages, which do not apply to you here.

Flat roofs are more maintenance. IMO - The roof is a functional and asthetic decision. I have a flat roof on my house due to building code/zoning reasons, but I would much rather have a sloped roof and it's abilty to shed the weather.

 

[billconner]

The IRC says for garage floors:

"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."

In my area, they dont require detached garages to be sloped. 1/8" in a foot is very slight.

Codes no longer require the step up to house entry in attached garages.

 

[Youngandfree]

The IRC says for garage floors:

"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."

In my area, they dont require detached garages to be sloped. 1/8" in a foot is very slight.

Codes no longer require the step up to house entry in attached garages.

My house was built in 2007. It has a 2 car basement garage with no step or curb. Just a normal entry door threshold.

 

[billconner]

My house was built in 2007. It has a 2 car basement garage with no step or curb. Just a normal entry door threshold.

I think that requirement was removed 20 or more years ago, maybe in transition from CABO one and two family dwelling code to IRC.

 

[duneslider]

I don't know where this explosion hazard stuff started but it isn't why garages are sloped. Mechanics shops are made with flat floors all the time, or flat with floor drains.

The step in the garage was always for water intrusion anyway. Commercial places don't have that requirement, so its natural that it came out of the residential code.

At my work the fork lift shop is all flat (well sloped to a trench drain) but not sloped to the bay doors. The wash bay is also not sloped to the bay door. Fumes are extracted with a ventilation system.

 

[03ranger]

Is your new garage/workshop attached to the house or standalone? If it’s attached to the house and has a garage door, it’s a garage and must have slope.

If it’s a standalone you won’t need a sloping floor, so long has there is no natural or propane gas installed. Check with the building dept. it may have changed in the past several years. We built in 2014.

As for the “flat roof” YES, most flat roofs are flat but not level. Another words there is a slope to the flat roof. Spray foam roof is great, it acts as insulation and reflects some of the heat.

 

[wssix99]

Codes no longer require the step up to house entry in attached garages.

Some codes do, some codes don't. It's important that the OP check their local codes as they could have all sorts of special requirements.

 

[wssix99]

Also, pros, cons of going with a “flat” roof?

One thought on the flat roof... If you are going to put in a lift, you can go with vaulted trusses or other arrangements with a pitched roof that give you shorter exterior walls and more vertical room for your lift. This will reduce the cost of your structure greatly. (The exterior walls are the most expensive part.) If you go with a flat roof, you will incur maximum expense to get your lift's vertical.

The other thing to consider is that if you go with a sloping slab, you need to account for that slope for your lift placement. (Your vertical clearance will be less at your lift location than at your garage doors because the floor slopes up from there.)

 

[brownbagg]

your going pay for level, a typical finisher cannot do level
level is classified as 1/8 in twenty feet, both ways

 

[dcg9381]

What construction type? For R-panel, I like to notch the foundation all the way around, we call it a "rat lip".
Our foundation is "flat" - but we do a 1" notch to fit the garage doors, which is a huge help. The other thing I call tell you to watch out for is make sure any adjacent concrete, such as sidewalk or driveway, needs to DEFINTELY be sloped away from the building. Especially at the entry door.

 

[wssix99]

I don't know where this explosion hazard stuff started but it isn't why garages are sloped. Mechanics shops are made with flat floors all the time, or flat with floor drains.

Other sites that discuss building codes, specifically, have enlightened discussions on this topic and have references that cite explosive fluids and gasses.

Commercial spaces and residential spaces are subject to different codes and requirements. A mechanics shop may have leeway in some areas that residential spaces do not, but they have much more stringent fire protection requirements. (For example, my residential garage is on commercial land but if I was to use it for commercial purposes, I would be subject to different codes, would need an extra 1hr of fire rating, etc.)

 

[PoorUB]

your going pay for level, a typical finisher cannot do level
level is classified as 1/8 in twenty feet, both ways

Yep! Where I used to work most of the shop was poured level. I thought it was funny because they would hose down the shop and there would be puddles every where and my bosses bitched about the quality of the concrete pour. He figured there should not be any puddles. I asked him if he was serious in thinking someone could pour a perfectly flat slab?! If you don't want puddles, you need to slope the floor. One shop I had the floor was sloped about 1/16" per foot and about 90% of the water would eventually get to the floor drain.

To the OP, Arizona? I would pour it flat. Snow country, slope it to a drain.

 

[The Tool Tyrant]

Slab: Level...I hate sloping floors!
Roof: Pitched...I hate flat roofs!

 

[Smoker]

Check your local codes. Sloped floors are required by code to mitigate explosion hazards. Gasoline vapor is heavier than air and the sloped floor evacuates any fumes out of the building. (Those vapors can linger in a flat floor room.) "Gas curbs" are also required for attached garages, which do not apply to you here.

Flat roofs are more maintenance. IMO - The roof is a functional and asthetic decision. I have a flat roof on my house due to building code/zoning reasons, but I would much rather have a sloped roof and it's abilty to shed the weather.

First I have ever heard of this. Certainly wasn't brought up by the city inspector in the last shop I built. My attached garage didn't have a "gas curb" either.. Can you cite the applicable code?

 

[billconner]

Other sites that discuss building codes, specifically, have enlightened discussions on this topic and have references that cite explosive fluids and gasses.

Could you provide some links to these "enlightened discussions"? I'm a regular at thebuildingcodeforum.com and they generally support just a minimun 1:96 slope for drainage, no step into dwelling, and generally no need to raise hot water heaters and such.any longer.

 

[no704]

Thanks for all the great replys. Sounds like a level floor for me! Will have about 8’ of apron before the sidewalk and street that will be sloped.
No trees in the immediate vacinity. Will talk to the builder about truss options.
Go 6” 4000 concrete?