Cost to add a pitched roof?


How much would it cost to pay a contractor to add a pitched roof to a house that currently has a flat roof? The house is 1,045 sq. ft. on the main level, and the house is a one story with a full basement. I understand that there are many variables but I just want something ballpark - ie does it cost $30k USD or more like $18k USD. I’m leaning more towards $18k.

The house is in Denver, CO so construction costs are probably about equal to national averages.



variable options is right…
Are you asking about re-roofing over a tapered flat roof designed to pitch water away from a flat area,
or are you asking about a small shallow-pitched wood framed roof designed to allow you to install a roof system that will shed water, and not change the look of the structure to dramatically?
Or are you asking for a truss roof with plywood with asphalt shingles to turn the design into a ranch style.
or are you asking for a roof frame design that would theoretically add a complete second floor to your existing structure?
Don’t forget to add into your estimates the costs to extend all penetrations , above the roof system to code, that being heating system vents, pipe vents, chimneys, etc…


The third option you listed is what I’m asking:

Or are you asking for a truss roof with plywood with asphalt shingles to turn the design into a ranch style.


Lots of variables. Will the roof be a simple two surface pitch or will there be valleys or angles? Are the ceiling joists arranged so they will work with new pitched roof rafters or will you need to tear out and replace your ceilings? Are the walls in good enough shape to stand tearing off and replacing the rafters?How much work will it take to blend the old siding into the new roof? etc.?
It’s really a two part question. The roofers here can give you an approximate cost for the roofing but the carpentry is hard to estimate without more exact information about the house…DaveB


It will be a simple, two surface pitch.

Let’s assume the ceiling joists are not arranged in a favorable manner.

I can handle the siding.


before I go too much further here, I need to know approx dimensions…38 x 28 sound about right?


If you want an accurate estimate you will need to contact a local builder or general contractor.

We can wildly guess and pull numbers out of our collective arse, but those numbers would mean nothing.

My wild stab in the dark would be around $23K for a 6/12 trussed roof.


Yes, 38 x 28 sounds about right. The house is a giant box.

I understand that I need to contact a roofer to get an accurate measurement. I’m just trying to get “ballpark” estimates right now.


although a truss rough is an option,
at 28 ft wide, using 2x8 rafters 16"oc and
5/8 plywood, 30 year shingles, membrane and 30#felt
stick built…I could be in the $20,000 range and be happy.
using truss is a trade off…more material costs/ for framing…less labor charge.

If your not restricted by zoning, etc,
stick built with a steeper pitch gives you
900 sq ft of bonus room space for a very small increase in materials costs.

just saying



[quote=“thebaycompany”].I could be in the $20,000 range and be happy.

How do you deal with the existing ceiling and joists? Do you replace the whole ceiling or try to save it and nail the new rafters to the old joists? A ceiling replacement would add quite a bit of time and money....DaveB


35 dollars an area foot just to frame and plywood to paper thats labor and material and provide you have a good place to attach a sill most flat roofs have an open back where the gutter is and the parapets are stepped so its hard to say you’d have to add that in too…i’d build a hip probably with a small overhang if its out of sq at all it would be alot easier that way you could fudge the crooked stuff at the soffit…another thing when you build a roof over a flat roof you’ll have to use trusses or when you stick build it you’ll need to put W’s (braces) in or it’ll sag its a totally different ball game if ever in pittsburgh go to kennywood across the street their is an Alzheimers foundation we put a hip on it extended the chimney etc… and had to use LVLs for the hip rafters since it was so big… it was way out of square so we put an overhang on it and some 6" commercial gutters on it


I would spend a lot of time lagging a ledger across the
area of the roof that is bearing the crow’s foot of the rafter cut, or the truss chord…usually, we just put a doubler on…lag the 1st one tight, then shim the second one. Collar ties work just as well here, but if necessary, I would build a kneewall under the ridge.
Prep the perimetere first, and the work is like new construction from there on. I like a hip in this case, makes the top floor look not so monstrous, and eliminates the gale end framing details. If it were mine, though, I would go with a 10-12 pitch and plan a nice senior citizens community in my attic.