New garage concrete advice please.

[rerod]

Hello folks.
I'm drawing up the plan view of my new build and wondered about how to draw slope, and how far back and to the sides from the door it should start. Ive read a good slope to keep water from traveling into the garage is between 1/16" per foot to no more than 3/16". The rest of the garage will be flat because I don't plan on parking my daily in it. But I need a couple of drains at the 1/3 and 2/3 mark just in case. I plan on a 2 post centered over the thicker rectangular section on the right and figured 8" and 5" for the rest. Specs call for 3000 psi.

Any suggestions of how far back and to the sides the slope leading to the door needs to start? And is my plan on thickness and psi ok? Should I place rebar throughout?

Thanks!

 

[CraigStu]

How about a recess in the floor for the door to settle into vs a slope? Otherwise is the door facing the wind in storms? If not, good seals work pretty well. On drains check w/ your local permitting peeps. Often they are worried about oil etc going into a drain in a garage and require crazy oil traps.

 

[rerod]

How about a recess in the floor for the door to settle into vs a slope? Otherwise is the door facing the wind in storms? If not, good seals work pretty well. On drains check w/ your local permitting peeps. Often they are worried about oil etc going into a drain in a garage and require crazy oil traps.

Thanks. Yes is does face south where most of the storms come from. I never thought of a recess.

All I know is that my dads garage had a huge bird bath in this spot. At least a gallon would collect right where his blade on the tractor sat.

Whats more difficult for a concrete guy to do? A recess, or 1/8" per foot slope for a couple feet back?

 

[kctgb]

If it were me I would have 1 inch in 10 feet. That is standard flow for sewer and drain pipes. When I replumbed my house the plumbing inspector told me that.

 

[BillK]

Is this a detached garage/shop or an attached parking garage ? When I did my 24 x 24 detached garage I had them make the floor level and flat. No slope at all. A sloped floor is a pain in the rear if you do anything that requires a level surface. That includes working on a car or building cabinets. Its a pain with wall cabinets etc etc etc.

All you need as far if you are worried about water is the section outside of the door to have a very slight slope on it. My attached garage faces south and all it has is a slight slope on the outside of the door and it never gets any water in the hardest rains. The door really should not leak anyway.

I have built two race cars in mine and done plenty of cabinets, bookshelves etc and having a level floor makes it a joy.

Think about it.

Just my opinion.

 

[Dig Doug]

I would slope the outside driveway, up to 1/4 per foot

you can also slight slope from the outside face of the garage door out to the outside face of the building ( whatvever your wall thickness is )

what happens in a flat area the water pools slightly then travels to any low points - this can even be under a garage door

 

[racecougar]

Agreed with the two posters above. Put a slight slope on the portion of the pad that is outside the door. It's not the easiest thing to spot, but you can kind of make it out in this photo. The pad slopes out from the door opening.

 

[manwithtools]

Put a slight slope on the portion of the pad that is outside the door.

Exactly what I had done on my floor that was poured last week.

 

[ConCretin]

The rest of the garage will be flat because I don't plan on parking my daily in it. But I need a couple of drains at the 1/3 and 2/3 mark just in case.

I wouldn't bother with floor drains if you're not going pitch the floor to them.

With regard to your overhead door sills, any competent finisher knows to pitch the slab away from the door but I suppose it won't hurt to ask.

 

[madison069]

There's two options that is common regarding the little area where the garage door sits, a slight pitched floor that's roughly 8-10" from the edge of the outside walls, or a recess area that's 1/2-3/4" deep that allows the door to sit inside it and it's lower than the rest of the garage floor. I selected the slight pitched floor instead of the recess due to possible trapped water/dirt in the recess.

The flatter you can make the floor the better, I was able to pitch a 32' long floor by 2" from the back wall to the front wall. You hardly notice the pitch until you study the cinder block stem wall. When it comes to leveling stuff, I'll just have to put 1/4-1/2" pieces of wood on the end toward the front wall to level it out.

I'm planning for a 4 post lift in the garage, so I can't comment on the 2 post lift requirements.

 

[70runner]

The lift area looks fine. I did 12" depth on mine and double rebar, 5" for the rest of the pad, 3500psi. Also, slope the transition between the pad and lift area. I marked the lift area on the pad formwork so the concrete crew would take extra care to make that flat. Came out well, but still needed a couple spacers under the lift posts.

 

[u2slow]

Yes to rebar.

I had the entire floor gently sloped to the door, no floor drains. But it is a bit smaller at 20x38'.

 

[rerod]

Also, slope the transition between the pad and lift area.

Thanks, but can you explain why you would want any slope in the lift area? The lift area is deeper but the surface flat.

 

[Codyboy]

Agreed with the two posters above. Put a slight slope on the portion of the pad that is outside the door. It's not the easiest thing to spot, but you can kind of make it out in this photo. The pad slopes out from the door opening.

I asked about sloping that area like I had seen on a friend's building.
The builder recommended against it due to rain being wind driven under the door.
They did a keyway for the roll up door and the rails to sit into. A 2x10 and a 2x4 laid flat and formed to the form boards.

 

[racecougar]

I asked about sloping that area like I had seen on a friend's building.
The builder recommended against it due to rain being wind driven under the door.
They did a keyway for the roll up door and the rails to sit into. A 2x10 and a 2x4 laid flat and formed to the form boards.

In six years, I've yet to have any water infiltration under my doors. I certainly prefer the slope to a ledge.

 

[Hank11]

OK then…
Slope and a notch.

For a south facing door I’ try to incorporate an awning of some kind. That will do a lot toward keeping the door and opening dry.

 

[manwithtools]

Thanks, but can you explain why you would want any slope in the lift area? The lift area is deeper but the surface flat.

He's referring to the sub slab preparation. You don't want a sudden step down in the under slab fill where the slap gets thickened, it should be a gentle taper.

Take a look at this post for further explanation of good practices on concrete. The Concrete Underground's Guide to Floor Slabs