Garage floor slope

[daithi]

Trying to decide on a slope/grade for my attached garage slab.
It's a small-ish space at 19 wide and will be multi functioning as a workshop (woodworking, metalworking and car maintenance, no parking).

To add a floor drain would require an oil separator etc for code - simply not going to happen.
Torn between adding some slope for drainage or pouring flat.

A permanent or any type of anchored hoist is probably not on the cards for me. I will probably look into something portable/not anchored in the future eg Quick Jack or a mid rise scissor.
Designer originally suggested 1/4" per foot for drainage purposes. I'm concerned that if I slope that much, a woodworking bench on casters or worst case scenario a car lift would roll. But maybe I'm paranoid?
If I reduce the slope to 1/8 per foot then I might feel safer, but is that even worth the hassle? At that point is it better to just pour flat and be done with it?

 

[Hooked]

When we built our garage in 1977 I had them slope the slab. Not much after moving in I grew to hate the slope. Should have left it flat since everything you want to set up on the floor must be shimmed to make it level (workbench, refrig/freezer, shelving, etc.). Surprising what effect 1/4" or 1/8" has when trying to make a surface level.

My $.02

 

[Skyman]

There is flat, and there is slope. They're different. Mine is sloped and I wish it weren't. It's not flat, and I wish it were.

If you don't plan to park vehicles in there that are dripping with rain water or melting snow, but are only concerned with puddles from occasional spills, I'd recommend having it be as level and as flat as it can be made. This is not a task I would award to the lowest bidder, as was clearly done by the builder of the place I now reside. I curse that unknown contractor at least once each week.

 

[Colin Len]

IMO, if you don't have a specific need for it to be sloped and if you can get away with it, go with a level rather than sloped floor. I think in many instances building code requires slope in garage floors although I think there are some workarounds. I really only see sloped floors as being useful in some rare situations - none of which I've ever personally encountered. Whereas I regularly encounter frustrations in my garage due to the sloped floor.

 

[tarmy]

Poured mine flat and no lip at the doors. I roll boats, tooling and table saw etc. out all the

 

[wssix99]

For an attached garage, the sloped floor is for keeping heavier-than-air gasses away from your house and work in tandem with the gas curb on your man door. (You have to step up into the house.) It is not primarily for water.

On a 1/8" slope, your concrete finisher won't be good enough to avoid puddles from developing. So, if you will bringing in snow and want the added benefit of water drainage, I would go with 1/4". If you put good casters on your tables/equipment, (filling in your saw cut joints and expansion joints also helps a ton) you won't notice the slope.

No garage floor is flat and there are ways to level any equipment you might bring in the future.

 

[larry4406]

In our new construction homes, the garages are typically 20-22’ deep. We slope 3” over this distance.

We then have the weather lip which vertically drops ~3/4” to create a recess for the garage door to sit in. Helps to stop driving rain from getting in. But a PIA with floor jacks. I prefer a ramp entrance at the garage door region.

 

[The Cobbler]

FLAT
smooth and even; without marked lumps or indentations.
"trim the surface of the cake to make it completely flat"


I poured level on mine & no regrets , but I don't park vehicles in there either

 

[daithi]

For an attached garage, the sloped floor is for keeping heavier-than-air gasses away from your house and work in tandem with the gas curb on your man door. (You have to step up into the house.) It is not primarily for water.

Relevant code for me allows for a slope OR a 50mm/2" curb. We are shooting for a 10' ceiling in the shop and 9' ceiling in the house. Achieved by a 12" step in the slabs, 12" curb in the garage and 9' studs throughout. So any slope in the garage at this point is entirely optional and only if I wanted to squeegee liquid out the door.

 

[carlaisle]

Having experience with both, I would go with flat. The smooth entry is glorious if your weather will permit it. You'll find out just how short that 10' ceiling is when you start moving around 8' long lumber and sheet goods. If planning on car maintenance, I would try to acquire the lift in advance so the floor can be planned accordingly.

 

[daithi]

Seems like the general consensus is to go without the slope. Thanks for all the input.

You'll find out just how short that 10' ceiling is when you start moving around 8' long lumber and sheet goods.

It is what it is. There are other design reasons that 10' is all I can do. Either way it will be a huge improvement on the shop I don't have today.

If planning on car maintenance, I would try to acquire the lift in advance so the floor can be planned accordingly.

Unfortunately I have nowhere to put it until the house is built. Besides that I'm trying to put every cent of cash aside for building the house. Lift will be a few years down the line.

 

[Beemer]

My residence has 1/8"/ft.
I am not sure if it's still the standard here but that was the minimum for "flat" roofs so it certainly worked in the garage.
I might have an affect on a potential lift though unless you got involved with non shrink grout, etc, but that would require investigation.

 

[nadogail]

Both of my garages were built before i was able to use them for anything but car storage. I built a small level platform to set the Freezer on, I made adjustments to the feet of the work benches and built a long plinth to mount the cabinets on making the the floor flat a d level. it is easier to shim a plinth than to build a slanted cabinet.

If i were to consider a floor mounted lift or hoist, I would use steel shims to make the floor under them flat and level. A long level and pressure treated lumber make building a sloped plinth easy.

 

[billconner]

Just for the record, the IRC, basis for most local codes, says:

R317.1 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.

Locally, for me that's enforced for attached garages but not detached. YMMV.

 

[u2slow]

Mine is sloped gently. About 2-3" over 37'. I think it's ideal. There's nothing important enough that needs shimming. 2-post lift also.

My only criticism is there's one low spot to the side of the OH door that puddles slightly.

 

[dave*99]

Both of my garages were built before i was able to use them for anything but car storage. I built a small level platform to set the Freezer on, I made adjustments to the feet of the work benches and built a long plinth to mount the cabinets on making the the floor flat a d level. it is easier to shim a plinth than to build a slanted cabinet.

If i were to consider a floor mounted lift or hoist, I would use steel shims to make the floor under them flat and level. A long level and pressure treated lumber make building a sloped plinth easy.

My 2 post Rotary lift manual suggests a combination of shims and non-shrink grout.

 

[bad_idea]

Attached garage I would slope.

When I had the slab for my 30x40x12’ detached poured, I had it poured flat. Has been great.

 

[jar944]

We then have the weather lip which vertically drops ~3/4” to create a recess for the garage door to sit in. Helps to stop driving rain from getting in. But a PIA with floor jacks. I prefer a ramp entrance at the garage door region.

That lip is a gigantic pain with a pallet jack as well.

 

[bad_idea]

I have a 1 1/2" deep pocket for the door openings. I live in a high wind zone (got the insurance to prove it) and love the pockets. Wind driven rain is a nuisance year round. I have not had major issues rolling things in/out in the 8 years the shop has been up.

 

[dave*99]

I like the lip as it keeps water out. We get wind driven rain in my climate.
I have 2 thin ramps for those times I need to roll my jet ski stand out of the garage.

 

[cliffcharb]

Code would likely dictate the final outcome. My area is required to slope towards the doors. When I built my detached we used the min 1/8” per foot.m

 

[Jackfre]

When I did my 30x34 the inspector asked how much grade was on the floor. I told him it was “as much as I want…” He chuckled and signed off. As you are not parking in there it is not a garage. It is a workshop. Pour it flat. The lip at the shop door is essential.

 

[mm08822]

I would go flat as others stated. Building things plumb and level is miserable on any incline.

The lip at the door is needed to prevent wind driven rain and melting snow.
Easy enough to cut a small beveled spacer to help casters get over it if needed.

Fill a barrel (on casters) with your saw dust and keep handi for spills/drippings from car.
Also can be used as a lightweight rolling table for tools/laptop/manual.