Concrete foundations across Toronto and the GTA
WSIB cleared|$5M liability insured
WSIB cleared|$5M liability insured

GSS guide

Suspended Garage Slab Cost: What Drives the Price

Footings, foundation walls, slabs, underpinning and framing in Toronto and the GTA.

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Supply and install

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In short: the cost of a suspended garage slab depends on its size and thickness, the engineer’s reinforcing, the shoring needed while it cures, how the concrete gets to it, and the season. This guide explains each one so you can compare quotes.

What is a suspended garage slab?

A reinforced concrete slab that spans over a room below, usually a cold cellar or a basement space under the garage. Unlike a slab on grade, it doesn’t rest on the ground, so it has to carry the cars above on its own, to an engineer’s design.

Slab edge finish, concrete slabs in Vaughan by Grand Structural Services
Concrete slabs by Grand Structural Services.

What drives the cost

  • Area and thickness. The engineer sets the thickness for the span and the load.
  • Reinforcing. Bar size and spacing follow the drawings. Longer spans need more steel.
  • Formwork and shoring. The slab is formed in the air and shored from below until the concrete reaches strength.
  • Concrete delivery. A pump is often needed to reach the garage.
  • The space below. A cold cellar may need waterproofing on top of the slab and drainage.
  • Season. Winter pours need heat and blankets.

How GSS keeps it efficient

  • We form and pour the suspended slab with the rest of the foundation, on our own forms.
  • We fabricate the rebar and supply the concrete at bulk pricing, then install both.
  • The engineer’s inspection is booked before the pour.
Underpinned basement finished slab, concrete slabs in Markham by Grand Structural Services
Concrete slabs by Grand Structural Services.

Questions people ask

How long before the shoring comes out?

When the concrete reaches the strength the engineer specifies. We don’t strip shoring early.

Is a suspended slab worth it?

If you want the room under the garage, yes. It turns dead space into a cold cellar or storage.

Building a suspended garage slab?

See our suspended garage slabs page, or send us the drawings for a free quote. Get a free quote or call (416) 785-7838.

Get a free quote

Takes 30 seconds. Upload your drawings for a faster price. We reply the same day.


Prefer to talk? Call (416) 785-7838

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Planning a foundation, an addition or a deeper basement?

Send the drawings. We reply the same day and build footing to roof on one schedule.