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Jim Hart · 04-28-2009, 03:39 PM

I'm adding a garage addition out the back of my existing garage. Should I, and if so how much, slope the floor? The addition will be 21' deep and I'll be storing my boat in it so I won't be parking a car in there that could have ice and snow melting off of it but it would be nice to get good drainage when I hose it down. If I do slope it then I guess I'd build the walls with slightly shorter studs as I move toward the rear of the garage (the higher concrete elevation) to keep my top plate level?

yesitsconcrete · 04-28-2009, 04:28 PM

when we built ours, we installed a drywell in the middle & sloped from all 4 corners 1":10',,, no mo' squeegee

Brik · 04-28-2009, 04:33 PM

Mine has a concrete stem wall (not sure thats what you call it) that is level and the floor slopes maybe 4" from the inside to the door. All the studs are same length and water wont pool against studs. I believe the foundation and stem walls were one pour and the floor another. Any foundation contractor that does garages will know what I'm talking about. I think this is standard practice design (around here anyway)

yesitsconcrete · 04-28-2009, 04:53 PM

a 4" DROP in 20' ? ? ? wow ! ! ! that's almost like having a half-pipe in your garage, isn't it ? ? ?

**Scuba_Dave** · 04-28-2009, 06:56 PM

Inspector here indicated 1/4" in 4'
My garage is 36' deep, so a 2 1/4" slope required
I'm going a little more then that I think

GBR in WA · 04-28-2009, 07:42 PM

Give a call to your local Building Department. They will check for property setbacks, variances, not over septic drain field, etc.

Some Counties will not allow drains instead of floor slope to door, a hard one to fix later. I understand that, if an explosion from your leaking gas ignited, and burnt down a house. I wonder if your Homeowners Insurance would cover that? Be safe, G

jomama45 · 04-28-2009, 07:42 PM

If your doing a slab on grade addition, I recommend what Brik said. We form curbs on all garage slabs (the ones with-out a block foundation), 0" in back to 3-3.5" at garage doors in 20-24' usually. It allows better protection for the studs (as stated) & is alot easier to frame.

Oh, & Yesitcrete, I have the same thing in my garage, but it's was put in 30 years ago, & not by me. In my area for the last 10-15 years, all drains in garages/workshops have to go outside to at grade. I think the idea is that there's a potential for oils, gas, chemicals to be in the drywell & there's a chance for explosion or something. Be careful when out smoking in your garage!

yesitsconcrete · 04-29-2009, 04:20 AM

have seen them as brik post'd, 'mama,,, grandfatherin's a beautiful thing, no ? ? ?

have 1 section of the garage that's pointing down,,, that's fine til the bride's car comes in wet & darinage runs to the nearest sole plate which was NOT p/t'd when this house was blt,,, need to regrade that area - will probably breakout & install another sump, too,,, **** never ends, does it ? ? ?

Brik · 04-29-2009, 08:39 AM

To be clear - My garage is new construction. Maybe 5 or 6 years old (does that still count as new?). The 4 inch drop, low end at the door of course, is not noticeable over the dept of the bays. Heck, I haven't measured it. It could slope 6". The floor of the garage is on grade of course. The house first floor is two steps higher.

Here is a picture of the corner of my garage near the door.

Jim Hart · 04-29-2009, 08:47 AM

So if I install a curb, I do that as a second pour? It is a slab on grade (with footings).

Brik · 04-29-2009, 09:08 AM

Mine, the 'curb' was poured as part of the foundation pour I think. The floor went in last. After the framing actually. Not sure why that sequence. I think the builder wanted he garage floor to look good when house was complete and didn't want the trades dragging ladders and stuff on it. Just a guess.

**Scuba_Dave** · 04-29-2009, 11:13 PM

I've always seen that lower "step down" on the outside of the door

If snow & ice melt won't it puddle at the door?
And if extremely cold freeze the door shut?

jomama45 · 04-29-2009, 11:28 PM

Quote:

Originally Posted by Jim Hart

So if I install a curb, I do that as a second pour? It is a slab on grade (with footings).

It' far simpler (& stonger) to pour ita all at the same time. It's just takes a little more forming/bracing & labor when finishing.

Brik · 04-30-2009, 09:33 AM

Quote:

Originally Posted by Scuba_Dave

I've always seen that lower "step down" on the outside of the door

If snow & ice melt won't it puddle at the door?
And if extremely cold freeze the door shut?

No - that lower step down is sloped to the driveway. The asphalt drive is flush with the lower edge of the stepdown. Never had a garage door freeze down, never had a puddle there. It just makes it hard for the kids rollerblades is all. The stepdown prevents wind blown rain from coming into the garage.