[FrankSmith]

I want to build an attached garage to my own house. The frost line in my area is 48”. I am curious if it is possible to trench pour a foundation in this situation. I would be willing to dig it wider or to flare out the bottom if that had to be done. Thanks for any feedback in advance.

 

[superseal]

You mean a mono slab? all in one one shot...

 

[brhokel606]

A 4' trench footing 12" min wide will work. Laying bar in a trench footing can be a bear but otherwise it will work. I have laid block for 2 courses onto of the trench footing to get my height for setting walls. I have also put up 2' tall x 8" batter boards over the trench footings and poured them all at the same time. Was a day of forming work but I do like the poured walls better.

 

[FrankSmith]

So the wall would be 12" all the way up? I would not do this as a mono pour. I would form it so it was poured 12" above grade and pour the floor later.

 

[griz]

Your footing wall would be free poured and as wide as you dug the footing. At grade line you form and pour whatever you want.

Saw two done that way, on fill, last weekend....

 

[jb4211]

So the wall would be 12" all the way up? I would not do this as a mono pour. I would form it so it was poured 12" above grade and pour the floor later.

What's the reason for not mono?
Are you running plumbing, electrical, etc. in flooring?
Just curious

 

[brhokel606]

What's the reason for not mono?
Are you running plumbing, electrical, etc. in flooring?
Just curious

I agree, build the wall your 12" above grade and pour all at once.

You build your forms over the trench and just float the edges of the foundation that sticks out each side. It will be buried below grade anyway. The part you want dead nuts level is the top of the forms. I can try and draw a picture and post if needed.

 

[FrankSmith]

Maybe I will pour all at once. Is the floor at the same height as the top of the wall in this situation or is there a way to hold an inside form that doesn't get in the way of the floor?

 

[griz]

You can do a mono pour with a raised stem wall.

 

[jb4211]

Is this garage for cars, storage or workshop?

Heated slab

 

[FrankSmith]

Cars. No plans for heat

 

[brhokel606]

The garage floor would be poured later. Footing and wall poured at same time I think was what was being suggested.

The other way is footing poured sametime as floor. Then either do a poured wall or block wall on top of the floor. I would not suggest this way. I prefer the garage floor seperated from the wall. Expansion joint between them and caulk it shut.

 

[wellbuilt home]

I trench pour all the time 4' at the bottom 2' +- for the footing, 20" wide bucket size .
Dig a nice footing , You could just pour to the top 4' of concrete but that is a lot of mix .
If the footing is tight to work in, I just dig around the outside and make a shelf to stand on .
I build additions and we don't have the room to dig footings and stash dirt around the yard .
Most of the time I like to keep the concrete down to one truck load .
I figure the extra money for concrete balances out with the digging and block/labor .
A job like that could be dug on the first day inspected on day 2 early , then poured and blocked the same day .
Some times the BI has me pin ridged blue board to the dirt so the ground can heave around the addition
john

 

[Warren]

Getting ready to build a big attached garage on my house. Spoke to inspector today, and he said a trench footing is acceptable. I like the idea of forming the top and not having any block. This will likely be a slow build as we are swamped. My mason is busy as well, so I can bypass him also. While I have not seen one done this way, I have heard of it and really don't see any major downside.

 

[Bull Trout]

Getting ready to build a big attached garage on my house. Spoke to inspector today, and he said a trench footing is acceptable. I like the idea of forming the top and not having any block. This will likely be a slow build as we are swamped. My mason is busy as well, so I can bypass him also. While I have not seen one done this way, I have heard of it and really don't see any major downside.

am I understanding correctly, earth formed footing, form boards for stem wall as apposed to a mono slab, or formed footing with block or poured stem wall on top?

rebar in the footing can be a pita, and estimating concrete is a little harder if the trench varies, but otherwise it is fine

 

[Warren]

am I understanding correctly, earth formed footing, form boards for stem wall as apposed to a mono slab, or formed footing with block or poured stem wall on top?

rebar in the footing can be a pita, and estimating concrete is a little harder if the trench varies, but otherwise it is fine

Yeah, but can't do the mono slab since it is attached to the house.

 

[Bull Trout]

trench footings work, I don't usually do mono poured stem walls, even with formed footings, always seem to end up fighting something that moves during the pour, and I would "savings" from combining loads isn't worth it to me, I would rather set forms on a level footing, we have poured footings in the am, had the walls inspected after lunch and poured them at the end of the day. All that being said, there is no reason trench footings don't work

 

[Tinstaafl]

It would still be essentially monolithic except where it's tied into the house. As long as the dollars make cents, I'd go for it.

 

[Warren]

It would still be essentially monolithic except where it's tied into the house. As long as the dollars make cents, I'd go for it.

Not really. The slab will be poured later. The trenches would still be down to frost depth. The biggest benefit I see is reduced excavation, and not having to time things up with the mason.

 

[Tinstaafl]

Oh, I misinterpreted. Still, why not go ahead and pour it as a mono? That would save you a bit of forming.