Your council pls.

[Allthunbs]

I am about to start building a 14x24 workshop (garage) in Quebec, near Quebec City. Where I am, snow load can hit 300 lbs / sq ft in a bad year and -40C is not unheard of. I have just taken possession of a 35 year old brick house with a carport. I want to add a workshop but I have to leave it usable for other uses as well.

I originated in Southern Ontario where a floating slab was just that, a slab of concrete floating on a bed of gravel. I get here, order some plans that will pass inspection and I find that a floating slab has footings and kneewalls.

The soil is compacted granular sand 85' thick. It has a compressive strength of 4.5 tons/sq ft undisturbed. It is porous. I can pour a bucket of water into a hole and I barely have time to start the stopwatch and the water is gone. My neighbour has a garden shed built on a slab (no footing etc.) and it hasn't budged in 10 years.

I want to do a straight slab. I was going to put a layer of gravel, a membrane for the concrete to cure on and 4" of concrete. Opinions? Frost lines here can hit 6'. I have bermed the soil up around the concrete block of the basement walls to aid in keeping the heat in during the cold months.

The slab will be 14'x24', 4" thick with mesh reinforcing. The gravel bed will be between 4" and 7", compacted by hand and I'll set level with the gravel.

Opinions? Can I get away with this or is this a fool's dream? I figured with the dryness of the soil I could get away with murder but maybe I'll end up paying the price?

Thanks for the help.

Allthunbs

 

[BooUrns!]

Is this workshop attached or freestanding? There's no point trying to get under the frost line for a detached garage. if it's attached, it will need the stem wall or piles. You may want to re-check what you ordered because floating slab and stem wall are completely different.

Try a beam in slab design. The perimeter of the slab is thickened and tapers inwards towards the center until you reach your 4" overall thickness. It's commonly used out here in AB where we get much colder and have clay as a substrate.

When you say compacted by hand, I assume you mean with a rental plate tamper?

 

[Allthunbs]

Is this workshop attached or freestanding? There's no point trying to get under the frost line for a detached garage. if it's attached, it will need the stem wall or piles. You may want to re-check what you ordered because floating slab and stem wall are completely different.

The garage is freestanding about 12' from the end of the house.

Try a beam in slab design. The perimeter of the slab is thickened and tapers inwards towards the center until you reach your 4" overall thickness. It's commonly used out here in AB where we get much colder and have clay as a substrate.

Just to give you an idea of how confusing this is, what you've described is called a monolithic slab on some sites on the 'net. That's how I got into this mess int he first place. I took a floating slab (in Southern Ontario) and ordered a plan for that. I ended up with a full foundation and supporting wall. Now I'm thinking I should have ordered a monolithic slab or a beam slab.

How cold do you get? I thought we held the record for snowfall and cold.

When you say compacted by hand, I assume you mean with a rental plate tamper?

Nope, I'm looking around for a bar with a flat plate on it. I see them on the PBS "How tos" on saturday morning (from Spokane.) Recently, Hometime used one.

I'm supposed to be lifting weights but I've been too lazy. Now I'm going to pay the price. :-(

Thanks for the help.

Allthunbs