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Old 10-06-2010, 03:57 PM   #1
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Garage floor slope.

Getting ready to pour a garage floor slab. Everything I've read says slope it 1/8 to 1/4 inch per foot toward the garage door. The garage is 28 ft deep so 1/8 to 1/4 inches per foot means the slab shoub be 3.5 to 7 inches higher at the end opposite the door. 7 inches sounds like too much both visually and from a walkability standpoint so the most I'm going to consider is 3.5".

Even 3.5" sounds like a lot but maybe it's ok over 28 feet?? Would you put in a garage slab that slopes 3.5" over a 28 ft run? I hate puddles so I do want it to drain well but I don't want it to look like a San Fransisco street.


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Old 10-06-2010, 04:39 PM   #2
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My Inspector told me 1/4" slope over 4'

so 7/4" of 1 3/4" for your floor


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Old 10-06-2010, 05:55 PM   #3
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That is a "check locally" item. The liquid gas or diesel has to drain outside if there is a leak or a fire. I would check before the pour, after concrete sets, it's very hard to change.....

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Old 10-06-2010, 07:19 PM   #4
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1/8 inch per foot is about 1 percent, 1/4 inch per foot is two percent. You would never notice either amount either visually or from a walking perspective, however water dripping off your car certainly would. A steep San Francisco street might be 25 or even 30 percent slope, that you would notice. Setting up a concrete pour for less than 1 percent is more difficult than you would think, it is easy to get low spots that trap water, chemicals etc. Two percent is easier to achieve with positive flow towards the door at all points.

However, as noted, you need to check with your building inspector or the local code enforcement official. Even if you don't need a permit.
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Old 10-06-2010, 08:26 PM   #5
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Thank you Gentlemen. I will give the inspector a call. It is good to hear that even up to a 1/4" per foot will be ok aesthetically. I've got plenty of stem wall height so there's nothing stopping me from going to that much grade. I just don't want it to look funny.
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Old 10-07-2010, 11:17 AM   #6
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Anywhere between 1/8" to 1/4" is ideal IMPO. As Dan stated, it's hard for the untrained eye to pick up on the minimal pitch, and 1/8" is borderline if the floor isn't extremely flat. Getting a floor very flat is harder than most people woul imagine.

Typically in a 28' deep garage, we'd keep the back 6-8 feet level to allow for storage, workbenches, etc... and use the remaining 20-22' for pitch to the OH doors. We're usually limited to a 4-4.5" max. drop as well though, due to constraints with frost depth, existing conditions, step(s) into house, etc...

One more piece of advise I'll pass on:

The floor should also pitch towards the OH door(s) in the short sections of wall on either side of the door. Typically about a 1/4-1/3 of a bubble on a level, or water is known to lay in those corners rather than run out.

I'd also recommend dropping the last 12-16" at the OH door a little more aggressively to keep driving rain from entering under the door. Oh yeah, one more, we brush/broom the small strip of concrete that will be outside when the OH door is closed, for uniformit with the rest of the driveway.
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Old 10-09-2010, 06:15 AM   #7
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wish you guys have placed our garage floor,,, unfortunately it runs to the back AND towards the finished wall which forms the family room,,, no p/t'd toe plates in those days, either did i ever mention they forgot or were ignorant about contraction jnts ? but those guys got paid & they're gone 1 of these days we need to get a shavemaster on it then o'lay it

some apron scarifying/grinding + a new gutter resolved it for now,,, good tips from everyone !

jo, are you going to vegas woc in '11 ?


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