Ground work question

[Emerson]

He guys. I have a question.

So I'm building a garage and it's come about due to necessity so the timeline is rushed and the time of year is not the best. I'm on the east coast of Canada and it's stating to freeze here daily and we've have a **** load of rain and about 1' of snow in the last week.

The area my garage is going is about 4' below the elevation of my house. I've had this spot picked out for years and I've slowly been filling it in with mostly good fill. I say mostly because some of whats in there is swampy clay that has to come out. What I've done right now is cleared the area of the about 2-3' past where I want my footprint of the garage. I've spread the good fill I had out about 1'-2' as far as I could. This Monday I'm renting a 1000lbs Compactor and I'm getting 30-40 loads of fill coming. What if what I've spread out is frozen? and I can't get the compactor on it before the fill comes. Can I put 6" or a 1' on top and start compacting? OR do I need to make sure that the 1st bit is good and compacted?
I'm abit stressed about it all because at 1st I was going with a full 4' frost wall but it's just out of my budget so I'm going with a engineered slab so the ground work is that much more important.

Here's my plan correct me as needed.

1. Monday morning have coffee be at rental place when they open to get compactor.
2. come home dig out clay area.
3. wait for fill replace dug out area and compact
4. compact the rest of the area if it's not a complete popcicle
5. use new fill to go out past garage footprint roughly 3-4' and compact every 1'
6. repeat until I get to grade.

I have a picture of where I'm at right now would that help?

 

[The Cobbler]

you're building a monolithic slab on top of fill? eeeeks

that spells trouble IMO

 

[ishiboo]

Um, 1000 lb compactor? To even consider this IF the fill was sufficient, you'd need a very large sheepsfoot compactor or something similar. You can't do this with a little dinky compactor.

Even with perfect compaction, you're at the mercy of the fill. What is it? Expansive clay? Lots of organics?

This sounds like a disaster waiting to happen.

 

[Emerson]

I'm guessing that's a no no.. Honestly this whole thing just stresses me out. I've been trying for almost a month to get this thing going and it seems like I can't give away $$. I have contractor come take a look, they take notes and say they'll get me a price and nothing. Out of 12 contractors I've got 3 prices back just amazes me. No ones told me this was a bad idea.

 

[Emerson]

Um, 1000 lb compactor? To even consider this IF the fill was sufficient, you'd need a very large sheepsfoot compactor or something similar. You can't do this with a little dinky compactor.

Even with perfect compaction, you're at the mercy of the fill. What is it? Expansive clay? Lots of organics?

This sounds like a disaster waiting to happen.

There's a 6000lbs unit I can get. the clay that is there has alot of organics in it. it's just a small section, it's been there for 6 years and is still soft as hell. My Backhoe sunk on it and soon as it was exposed.

 

[Emerson]

So. is a full frost wall the best idea in this situation?

 

[matt_i]

I think if any part of it freezes with moisture its going to be trouble. The freezing is expansion of water as we all know and as the water abates its going to shrink back. Perhaps a small amount but added and multiplied over a lot of volume I think trouble. In my opinion very unlikely mechanical compaction can drive the ground-moisture out of freezing state unless put in very thin and heavily worked.

My personal advice is to wait this out until the spring melt is done and you have more stable weather.

I think the frost-protected shallow foundation is a good thing if the established details are followed closely, but working in mushy conditions *****, 2x that when freezing.

 

[readhead]

This is a wreck waiting to happen. I understand the urgency but the end result could be a disaster. Buildings get built year around but in your case if you want to proceed I would strongly recommend you remove the existing material down to natural grade and below the frost. Protect the excavation with blankets. Build a stem wall foundation and build a garage.

Now that being said it doesn't sound like that will fit the budget. My recommendation would be to figure out a way to get through the winter and reassess the project in the spring.

 

[RWorth]

how big a garage, and what are you doing in it.

big difference in prep between a 12x 20 and a 30x40.

just a couple of facts, you can't compact anything your backhoe sinks in. nothing wet, and nothing organic, and definitely nothing frozen.

 

[bcoke]

I second what has been said ......But the major issue I see is a rushed timeline.....Haste makes waste so they say and the foundation of any building is most important to the success of same...I know life is like toilet paper, the nearer the end the faster it goes!!!! Get a soil analysis and a plan for the correct way to support a monolithic slab.....compaction ,drainage,stone etc then wait for the proper season and then and only then throw money at it, it will be cheaper in the long run and a better product being built in reasonable weather conditions......IMHO.........bobbycoke

 

[Emerson]

Thanks for the input guys. I think I'm going to bring in the pros. I'm going to get the site done by people who have the proper equipment and I'll also be going with a full frost wall. Looks like I'm headed to the bank come Monday morning.

 

[ForceFed70]

What you've done isn't "bad". You just need to keep it in mind when planning..

My recommendation in your case is to avoid a monolithic pour. As you've mentioned, that means using stem walls. Dig the stem walls down to virgin soil/depth. This will result in you having what's called a floating slab. There's less weight on the slab, so it's less prone to settling, and because it's floating it can actually move a little if needed instead of just cracking. You'd still want to compact the **** out of it tho.

You cannot compact frozen ground. Also, soil with moisture in it (most soils) that freezes after compaction is no-longer compacted - keep this in mind.

With statements like 40-50 loads of fill, you must be planning a large shop and it doesn't sound like you have a lot of experience doing this. Going with a pro is probably a good idea.

 

[ard]

Thanks for the input guys. I think I'm going to bring in the pros. I'm going to get the site done by people who have the proper equipment and I'll also be going with a full frost wall. Looks like I'm headed to the bank come Monday morning.

Glad to read this. Please dont 'shop' for the answer you want....

Id try to get an engineer out to design the foundation, or at least give you the rough options- not simply a contractor to bid it. Not sure what that costs, but balance the cost now with a mess in your shop for the next 20 years.

 

[bruincounselor]

I'm planning my own build for spring and it seems some folks can help me (excuse the hijack):

Mono slab or foundation?
38x24'
Radiant heat (eventually, tubes for now)
Single story
Heavy clay gumbo soil
Build will be above existing grade where old garage sits.

Thoughts? I will be hiring out concrete work and doing the rest myself.

 

[n20junkie]

Op may end up with the leaning garage of canada when its all over. I would build on a foundation/stem wall or wait until spring. Starting now may end up in a lot of wasted money.