Concrete questions

[993James993]

Hi Everyone,

I'm planning for my (hopefully) soon to be started project and have a few questions about the concrete slab/foundation.

The garage will be a single story wood frame structure set on a 22'x22' monolithic slab. I want to add a two post lift at some point in the future and that calls for 3000PSI concrete that is 5" thick.

Here are my questions related to the concrete and the slope:

Can I leave the rear third of the floor flat and then have the front two thirds sloped? The cars will be parked in the front two thirds and there will be a workbench in the back, along with the side exit door. I am thinking of starting the slope at a control joint.

Can I get away with a 1/8" drop per 12" or is 1/4" slope required? (The difference is the height of the stem wall at the front of the garage.)

The footings will be 12" wide and up to 18" deep. The slab will be 5". I want all the proper rebar and steel reinforcement, along with anchor bolts for both the sole plates and the shear wall.

Any ideas for the cost of this, taking into account that the contractor will dig all footings, set up the forms, finish the slope, add control joints and finish the slab? I realize this will vary from area to area.

I hope to hire someone with lots of experience and references, and I'll look at their work before choosing a contractor. Any other tips in selecting a good contractor?

Years ago I had an addition built and the concrete work was not what I expected. I don't want that disappointment with this project.

Thanks for your suggestions!

Jim

 

[Junkman]

When I built my garage, I was under the impression from the contractor that a sloped floor was part of the code. When I talked to the building code enforcement person, he told me that there was no code requirement to having a sloped floor. I then had the floor poured flat, and have never seen a reason that I would have needed a sloped floor. I would advise against it, unless in your area it is a building code requirement.

 

[ScaldedDog]

Where are you?

 

[993James993]

I'm in Arizona. Code here calls for a slope but it is not specified.

Thanks!

 

[ket-tek]

When I built my garage, I was under the impression from the contractor that a sloped floor was part of the code. When I talked to the building code enforcement person, he told me that there was no code requirement to having a sloped floor. I then had the floor poured flat, and have never seen a reason that I would have needed a sloped floor. I would advise against it, unless in your area it is a building code requirement.

My builder also said it was a requirement for my area. I didn't question it as it does make sense in a way. Now I wish I had checked in with the county first because I'd prefer it to have been flat..

The snow and rain off the cars still just sits on the floor even with 2" of drop across 28'... It seems like it would have to be a serious flood for the slope to do anything. I don't know if once I epoxy and clear coat the floor if the water will drain better or not than bare concrete.

 

[FunfDreisig]

I'm in Arizona. Code here calls for a slope but it is not specified....

Arizona requires a slope Must be to drain away all those monsoon rains

I can understand how code might require a slope on an attached garage -- to keep water out of the main structure. But wonder about the logic of requiring a slope on a detached garage.

In any case I'd make the slope as small as possible unless you really plan on hosing down the place regularly

Funf Driesig

 

[usa#1]

Check with your building inspector to see what's required. You may be able to just recess the concrete area at the doors to prevent water from entering the building and leave the interior flat. I wouldn't want a sloped floor if I could avoid it.

 

[Gary S]

When I built my garage, I put in 1" of slope for every 4' of floor run. I love it. Now the water that drips off the vehicles runs to the door instead of sitting on the garage floor and having to be constantly cleaned up. I'd never build a garage with a level floor again.

 

[c39er]

Can you catch your sockets rolling to the door too?

 

[jlbota]

I have a large section in my 30X40 garage that is sloped and I am tearing it out and repouring it because it makes it almost unusable. There is a drain in the floor which is fine. But it is so sloped it makes it impossible to even sit on a chair with wheels.

I am going to put a lift in this new poured area and I can't wait until its done!

So I would say if your going to slope it make it very minimal.....you can always squeegee the water out the door worst case.

 

[motofly196]

When I form concrete, I set the forms to just "break the bubble" sloping away from the house. To prevent any water collecting or pooling near the footings of the house. It doesn't require alot of slope to get water to flow...not the kind that is even noticable unless you put the level on it. Should look like this |()| if that was level.... |(|) and like that if "breaking the bubble"... not sure if that made sense or not... Really hard to explain on here... but not hard in person.

Scott

 

[Mike in Ohio]

In my 30 x 44 I had 1/4 of it sloped the rest is flat. An area about 15 by 20 slopes to a drain in the center of that area. That is the only area that I park a road vehicle in. The rest is antique tractors and shop space. If you are going to put floor drains in, put one in in the middle of each bay. I put one in the center of a 2 car garage and the mess seems to sit right by the drivers door of both vehicles( 1 backed in , 1 driven in). Biggest mistake I made in my attached garage.

 

[RobSmith]

Sloped floor ? Not a good idea. My garage has a grated drain across the front of both doors and a tiny 1/2 " drop recess where the roller door sits before rising to the garage floor level. One big rain storm saw 4" water running down my drive and the little
5" x 5" x 5" grated drain slowed the flow enough to stop it from flowing above the 1/2" lip. Had worse rain since and still no water in the shed.

 

[lilcuda]

I must chime in here because I got screwed by an architect that made me beleive that 1/4" per foot is code. Here in CA, it is not. I ended up with 1/4" per foot over 20 feet. It ***** for jacking up cars. Do not do 1/4" per foot unless you absolutely have to. Spend the time to research it. Once it's poured, you can't change it. I would go with no more than 1/8", preferably 1/16" if they'll let you get away with it. It's more than enough to drain any water that comes off your car when you park it after a rain storm. Think about it - is it going to rain inside your garage? If it does, you have more serious problems than what the slope of the floor is.

Check out how my floor looks:

http://home.earthlink.net/~lae4503/garage/

Good luck!

 

[mikeyr]

my garage is 20x20 and I had to have a slope but the attached 22x24 addition could be flat since it was a "workshop" and not a garage.