30x40 Build advice

[kylemac]

Hey Guys

Im new to TGJ I just wanted to see what you guys suggest on my build.Im in Ontario and doing a 30x40, 12 foot ceilings, insulated slab with radiant and just trying to figure out what my plan is for footing foundation. My township says I cannot do slab on grade due to size and have to do either engineered slab or classic footings, foundation, slab. I'm doing the whole build myself and was looking to contract out just the foundation side of things but prices I've been getting have been quite high, had about 4 quotes now and none of them have been what I though they would be. So im thinking about excavating, forming up a footer and laying block for foundation walls myself (father in law is stone mason so block walls should not be an issue) I have a friend who is also lending me his mini ex but im just wondering how easy it is to level up a trench for footings? I was planning on just excavating a trench and leaving the middle so that I can avoid as much tamping for the slab as possible, but wondering if this is something I should have someone come in and do or if I should just go for it and give it a try? Also does anyone have anything against laying block for the foundation below grade? I have read a few threads on here of guys suggesting not to do it but it definatly seems like the best cost saving way to go.

Thanks

 

[DieselO]

I'm in Southern Ontario and built a 32 X 30 shop last year. My foot print was bigger than the town would allow for floating slab as well. But all i had to do was have a engineer draw me a suitable slab with proper rebar through out.

Drawing cost $400.00 from engineer

Doing a footing with blocks on top is an excellent way to do it as well. and it also allows you to do the actually floor por after roof is on to protect from too much sun and or rain

 

[kylemac]

I'm in Southern Ontario and built a 32 X 30 shop last year. My foot print was bigger than the town would allow for floating slab as well. But all i had to do was have a engineer draw me a suitable slab with proper rebar through out.

Drawing cost $400.00 from engineer

Doing a footing with blocks on top is an excellent way to do it as well. and it also allows you to do the actually floor por after roof is on to protect from too much sun and or rain

How much did the slab pour end up costing you if you don't mind me asking? did you just lay bottom plates right onto slab or have a bit of a stub wall?

 

[Keithinsc]

Don't worry about leveling the trench for the footers, just make sure it is deep/thick enough to satisfy requirements, and that you order enough cement. We used to use a soupy mix so the top of the footer would self-level. Our masons wanted the finish on the footer left a bit rough so the first course of motar and block had some 'tooth' to hold onto.

I like 2-3 courses of block above the grade for the stub wall. That way the framing and siding is high enough that rain doesn't splash against it. And it is high enough that (some) of the snow isn't bearing against the siding. Cost usually dictates if a stub wall is used or not. But if you have a mason around, the cost would just be materials and beer!

 

[kylemac]

Don't worry about leveling the trench for the footers, just make sure it is deep/thick enough to satisfy requirements, and that you order enough cement. We used to use a soupy mix so the top of the footer would self-level. Our masons wanted the finish on the footer left a bit rough so the first course of motar and block had some 'tooth' to hold onto.

I like 2-3 courses of block above the grade for the stub wall. That way the framing and siding is high enough that rain doesn't splash against it. And it is high enough that (some) of the snow isn't bearing against the siding. Cost usually dictates if a stub wall is used or not. But if you have a mason around, the cost would just be materials and beer!

thanks keith, that was the plan, was going to do minimum a foot above grade possibly two, when they did your block wall did you fill any voids on the block? did they use any vertical rebar in the block?

 

[Keithinsc]

thanks keith, that was the plan, was going to do minimum a foot above grade possibly two, when they did your block wall did you fill any voids on the block? did they use any vertical rebar in the block?

No rebar in the block cells. But, we would drop a piece of all-thread into the cell, or a J-bolt and cement in place. About every 4'. Use those to anchor the sill plate. Just do some planning ahead when you place the anchor bolts. PITA when they land right under where you need to place a stud for the wall!

We did fill a few of the blocks with crushed beer cans.....no idea where so many came from!

 

[kylemac]

No rebar in the block cells. But, we would drop a piece of all-thread into the cell, or a J-bolt and cement in place. About every 4'. Use those to anchor the sill plate. Just do some planning ahead when you place the anchor bolts. PITA when they land right under where you need to place a stud for the wall!

We did fill a few of the blocks with crushed beer cans.....no idea where so many came from!

haha thanks, that's about all we will be able to fill them with as well, gotta add some lateral support

 

[matt_i]

I rented a mini-ex and dug the trenches.

Key to not over-dig is a rotary laser level with a sensor that can be attached to a post (2x2 or piece of PVC pipe) that goes down into the trench (need a helper). I bought one for the project, while I haven't used it since its a fantastic tool and will be used again in the future.

Where I screwed up was expecting the trenches to be straight and square long enough to finish. We had crazy rain for ~6 weeks after which collapsed all of the perfectly dug trenches and caused me endless hours of mucking out super heavy wet clay with a shovel and my upper body strength got to an unprecedented personal level lol. Had I taken time off enough time to complete the excavation-to-finished pad footing then my life would have been much easier Also I could have dug a "low point" outside of the normal building rectangle that would have been useful as sort of an accumulation pond for water to go.

I read about soupy concrete above and I'm personally against it because it causes it to be weak and super cracky. This is the main support surface for the entire building & establishes most all of the dimensional stability of the structure forevermore...I like to think thick strong massive rebar-filled footings.

If you google search 'garagejournal tool crib of the north' you'll find details and pictures.

 

[jonshonda]

Not that is makes a huge difference, but planning for finished building sizes in multiples of 4' or 8' provide the best yield for materials.

 

[Smokeem]

Could you possibly to a mono slab with turned down footings? Basically your typical 4-6" slab with the outer edged thickened to get below your local frost depth. You should only need a 12-16" wide on the perimeter thickened to meet structural load. See a lot of guys do this type of slab for outbuildings. Sure makes it easier to only have one pour.