Engineering Firm for Garage Concrete Slab ??

[reddeerguy2015]

Hey all,

Planning on starting a garage build this spring.

Red Deer County allows up to 728 sq ft for a monolithic garage slab pour (5" slab with thickened edges).

So this is equivilent to a 26' x 28' structure.

However this is not quite big enough - I'd like to get bigger if I can. Ideally I'd like a 32' x 40' structure with 10' walls.

However, they're saying anything larger than 728 sq ft requires 4' frost walls under your slab....OR an "engineered slab".

I've phoned around and it seems with most concrete companies the price almost triples as soon as you add the pony walls.

So I was wondering if anyone has had an engineered slab signed off on without the use of frost walls. Basically a slab on grade pour, with whatever additional requirements may be needed??

Just looking for ideas or solutions around the frost walls, strictly for budget purposes, yet still want a legit structure at the end.

If all else fails I'll settle for the 26 x 28, but curious what everyone else has done. Thanks.

[Ice Fishing Maniac]

My garage is 24x28 with 10’ walls (I wanted 26 but gas line was in the way). Built on a monolithic slab with 24” wide thickened edge.

Nothing wrong with footings with foundation wall and floating slab.

Also dependant on the type of soils the foundation will be on.

Talk to a structural engineer and a geotechnical engineer. You will probably need a foundation soils inspection for your permit from the geotech engineer. It doesn’t cost too much .

[2011laramie]

Guy i used to work with built a 40x80 or 40x90 shop with the thickened edge slab. No pony walls. It was signed off by an engineering firm. This was up near la biche, so different county.

[Sneeze]

Many counties and cities publish thickened edge designs that will meet what your municipality wants.

Secondly - it won't be crazy amounts cheaper than 4' walls. Actually it will probably cost more and won't be as nice.

Have a look at some thickened edge designs. They are concrete/rebar/gravel hogs.

[reddeerguy2015]

Originally Posted by Sneeze

Many counties and cities publish thickened edge designs that will meet what your municipality wants.

Secondly - it won't be crazy amounts cheaper than 4' walls. Actually it will probably cost more and won't be as nice.

Have a look at some thickened edge designs. They are concrete/rebar/gravel hogs.

The municipality wants 4' frost walls for slabs larger than 728 sq ft.....OR an engineered slab that is signed off on.

Who do you guys recommend for an engineering firm??

What are typically the steps involved in this process ??

[brendon444]

What kind of prices are you getting quoted if you don't mind me asking? Will be doing a similar project in Lloydminster which requires the same requirements over 592sqft though.

[MR.K]

Not sure if this helps you but when i built a slab on grade house (32' x 65') I learned that recommendations were for 4'-5' frost walls (but in less favorable soil conditions piles were the recommended practice)

This tells me that piles are better (also no cribbing required for footing or wall-which saves money)

I put piles in every 6'6" (10' deep and 12"dia.)

[alpineguy]

Originally Posted by reddeerguy2015

The municipality wants 4' frost walls for slabs larger than 728 sq ft.....OR an engineered slab that is signed off on.

Who do you guys recommend for an engineering firm??

What are typically the steps involved in this process ??

Mike Richards is a good guy. Have used him in the past on wood foundations.
He has expanded and is usually quite busy but would be worth a call. Located just south of Red Deer.
www.richardsconsulting.ca/

[reddeerguy2015]

Originally Posted by brendon444

What kind of prices are you getting quoted if you don't mind me asking? Will be doing a similar project in Lloydminster which requires the same requirements over 592sqft though.

10k for 728 sq ft, 25k for 729 sq ft. That's to have a contractor come in and do everything, including haul fill and site prep.

However this is a project I want to tackle myself. I have access or own the required equipment and tools to do all site prep and fill. Would just need a couple extra hands come pour day. I would prefer to stick to slab on grade as that's what I'm familiar with.

[calgarychef]

If you have the equipment..... Excavate and pour the walls extending up so your walls will be built a boor above grade. Fill the hole inside with pit run then road crush the last 6" and pack the bejesus out of it, including the pit run. Pour a floating slab within the walls, and you can even do this part after the structure is up.

[jpohlic]

Are you going to heat this garage in the winter?

Slab on grade structures that are not heated are prone to movement due to ground frost. Sure, they may be engineered and structurally sound but you could end up with doors that won't open/close properly.

Slab on grade structures that are heated will lose heat through the slab and thickened edges, keeping the ground from freezing and hopefully keeping the slab from moving.

I designed an engineered slab on grade home for a client who built the slab one summer and then started the home the next year. He did not hoard and heat the slab over the winter and the next year the slab was no longer level.

My dad has a big shop that's not engineered but we did a thickened edge slab with a dense rebar grid tied to a bunch of piles at maybe 8-10' on center. I don't think he's had any issues with it moving but he does heat it in the winter.

I recommend an engineered grade beam on piles over an engineered slab.

[jpohlic]

dbl post

[denied access]

Put in a pole structure and pour the floor in it.

[Ice Fishing Maniac]

Out of Red Deer you can look into Parkland Geo. They are a civil engineering / geotechnical and materials testing firm. If not try WSP. I think they have an office in Red Deer as well.

They can help geotechnical and maybe structural. Both should be able to direct you to structural engineer if they don't have any on staff.

[reddeerguy2015]

Just to clarify, I do plan on heating both the garage and the slab.

I'm not opposed to having the frost walls first and building the shop on top of them, then having a floating slab poured in after the fact.

Has anyone gone this route?? Is it recommended??

Just figured I could split my concrete costs into two separate bills at two different times, to keep prices manageable.

[Ronji]

We have built a number of concrete slabs. We Engineer all of them.
The slabs are thick around the exterior and we always install them on screw piles. We have used this method for both heated and unheated slabs.
They never move or crack with the screw piles in them. One customer had car 2 lifts installed on top of a heated floor.

[reddeerguy2015]

Originally Posted by Ronji

We have built a number of concrete slabs. We Engineer all of them.
The slabs are thick around the exterior and we always install them on screw piles. We have used this method for both heated and unheated slabs.
They never move or crack with the screw piles in them. One customer had car 2 lifts installed on top of a heated floor.

That sounds like a really simple, easy workaround. Who is the company you use to sign off on them??

How many piles do you use on a slab?? Just around the perimeter or throughout including the center of the slab as well ??

[Trochu]

Originally Posted by reddeerguy2015

That sounds like a really simple, easy workaround. Who is the company you use to sign off on them??

How many piles do you use on a slab?? Just around the perimeter or throughout including the center of the slab as well ??

I would think the number of detached garages/shops having structural slabs in Central Alberta would be few and far between.

[reddeerguy2015]

Originally Posted by Trochu

I would think the number of detached garages/shops having structural slabs in Central Alberta would be few and far between.

Just don't want to run into any issues when we eventually sell the place.

So prefer to have to proper permits in place along the way.

[brendon444]

Originally Posted by Trochu

I would think the number of detached garages/shops having structural slabs in Central Alberta would be few and far between.

Considering it’s required in almost every jurisdiction that requires a permit over certain size most state 55m2 or 592sqft as that is what Alberta code says. How are they getting around this? Sounds like it must be common practice to get it signed off.

Curious to hear the price you get quoted to sign off on the slab with piles as this sounds like the cheapest option that is structurally sound.

[Smokinyotes]

My shop has a 5-1/2’ frost wall but no piling under the pad and I have hairline cracks from each corner of the shop to the sump. If I was to do it again I would definitely put in pilings.

[2011laramie]

If you got more than 20 acres, some buildings can magically become "farm status" and dont quite follow the same rules.

[Trochu]

Originally Posted by brendon444

Considering it’s required in almost every jurisdiction that requires a permit over certain size most state 55m2 or 592sqft as that is what Alberta code says.

A structural slab? I thought most were on screw piles or footings and utilized a slab-on-grade. Maybe I'm wrong on this, but structural slabs get expensive pretty quickly.

[brendon444]

Originally Posted by Trochu

A structural slab? I thought most were on screw piles or footings and utilized a slab-on-grade. Maybe I'm wrong on this, but structural slabs get expensive pretty quickly.

My county bylaws says garage over 55m2 requires an engineer to stamp the drawing if it’s not using 4’+ frost wall and footings.
Wondering if anyone has experience on the cost?

[expedition]

Originally Posted by Smokinyotes

My shop has a 5-1/2’ frost wall but no piling under the pad and I have hairline cracks from each corner of the shop to the sump. If I was to do it again I would definitely put in pilings.

if they are hair line size they are shrinkage cracks . Concrete shrinks as it cures. The more water added the more the shrinkage cracks.

[liar]

Originally Posted by reddeerguy2015

Just don't want to run into any issues when we eventually sell the place.

So prefer to have to proper permits in place along the way.

for that reason definitely get the proper permits and reports in place .

[Trochu]

Originally Posted by reddeerguy2015

Just don't want to run into any issues when we eventually sell the place.

So prefer to have to proper permits in place along the way.

I'm not suggesting to not get permits. I'm suggesting I don't think the majority of detached garages are on structural slabs.

[liar]

we had a firm out of edmonton do ours , 36x30 . i will try find the name . after 8 years things get buried but i will look . fyi slab is good as new-no cracks .

[Arty]

Originally Posted by jpohlic

[...]
I recommend an engineered grade beam on piles over an engineered slab.

I'd second the grade beam on piles - with prestressed hollowcore on top. No pours, no fuss, no muss. Maybe a diaphragm topping at some point.
http://www.spancrete-sma.com/ps_hollowcore.php

[Trochu]

Originally Posted by Arty

I'd second the grade beam on piles - with prestressed hollowcore on top. No pours, no fuss, no muss. Maybe a diaphragm topping at some point.
http://www.spancrete-sma.com/ps_hollowcore.php

Have you ever seen hollow core used on a single storey structure?