Cost to build 15 x 15' room onto 2nd storey flat roof of Toronto semi?

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Posted by: from Toronto
11/22/2015 at 3:13:46 PM

But without any of the finishing (i.e. without drywall, plumbing, electrical). Just the required reinforcement to the existing structure, framing, and roof. It's a typical brick-frame semi in the old City of Toronto, 100 years old, with a pitched roof on the front half, and a flat roof on the back half, over which the addition would be placed. There is a fairly narrow driveway for access.

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Peter from Ace Renovations in Brampton
Date/Time11/22/2015 at 6:32:38 PM

Hi !

My company ( I'm the owner ) did exactly this type of project two years ago on Merton St. Davisville and Mt. Pleasant area. We removed the attic above the existing two storey 100 year old semi and protected the neighbour's attic with a firewall. We then built the new third floor with a flat roof due to height restrictions. The new floor covered the existing second floor and a one storey flat roof kitchen at the rear.

The kitchen had a bad foundation so we used 3 helical piles screwed into the ground outside the rear wall then slid steel beams under the kitchen onto the original house foundation and on top of the piles. That part of the job cost $ 10,000. Hopefully you won't need that but check the quality of your foundation everywhere.

Inside the house my engineer had us beef up the corners by adding built up 2 x 6 posts. We used wooden I-beams for floor joists avoiding any internal posts. We gutted and remade a bunch of rooms as well as adding the third floor master bedroom, bath, laundry, storage and den. The total cost was $ 150,000 plus a new furnace/AC and new back deck with roof. The house sold this past summer for $900,000.

In your case, if you don't need any extra foundation reinforcement, just a straight up framing job, then you can budget about $ 10,000 including engineer/permit costs.

Committee of Adjustment will cost $ 1,500 if you are closer than 6 ft. to the property side line and apply for a variance.

Hope this helps!

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Date/Time11/23/2015 at 9:45:40 AM


Thanks very much for your inquiry. The estimate for that job would be about $45K

Hope that price meets your budget requirements?

Please do not hesitate to contact me if you have any other question.


Mike Messiah, P.Eng.

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Paul in Toronto
Date/Time11/27/2015 at 11:30:31 AM

Peter - thank you. Did you mean $100 k, or is it really $10 k? I ask because I figured a new roof alone would be that price...seems quite low.

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