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Community and Q&A

New Construction: When to Build the Roof

green654 | Posted in General Questions on

When does a roof get put on during a new build? Does the roof go on last after the rest of the house has been framed? Or does it go up right away once there are walls and then the rest of the house/rooms framed after that?

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  1. Expert Member


    Some high performance builders install continuous sheet goods on the underside of the trusses as an air-barrier before framing interior petitions, but the vast majority of houses are framed sequentially - that is all the floors and walls, then the roof last.

  2. trystanherriott | | #2

    I’ve built several stick-framed cabins, and I always prioritize getting the roof framing up and roof sheathing and underlayment on ASAP so I can get to “shedding water” status. Clearly you need to have bearing (and gable) walls (mostly) framed and (at least partly) sheathed before you start framing the roof.

    This is the same approach we took when carpenters framed our house. There are no interior bearing walls in our house, so it was a race up to the exterior wall top plates, set trusses, roof sheathing, underlayment…then sigh of relief that it’s no longer going to rain inside your house!

    Some of this may be moot with larger/faster framing crews, but with a small crew it can make a lot of sense to take the race-to-the-roof approach.


  3. green654 | | #3

    Our builder has framed out entire house from bottom to the top. Roof is going on last. It should be up in the next week or so. In the meantime, we’ve had sssooooo much rain and the wood framing, sheathing, studs are now growing mold. Very upset because I’m incredibly sensitive and allergic to mold. Not sure what we are going to do now.

    1. Expert Member
      MALCOLM TAYLOR | | #5


      I'm not sure you can blame your framer for working in the accepted sequence of construction. Unfortunately water damage and mold are a real possibility when you decide to built a house at this time of year.

  4. trystanherriott | | #4

    I’d suggest cleaning the moldy areas with Concrobium and consider covering framing as needed with an appropriate primer or paint. Hiring someone who specializes in this kind of work can be a pretty good approach.

    Don’t let your concerns about mold be dismissed. Yes, mold and spores are everywhere in the world, but you don’t want them in/on your house framing as you’ve described.


    1. andy_ | | #6

      We just had a whole thread about this, but yes...remediation is a good idea, but also that it's not necessarily a long term issue once the house is dried in and the surface mold treated.
      If money were no issue, I suppose we could erect giant circus tents over the work site before building and condition the space. I guess that's the sales pitch for prefab?

  5. Expert Member
    Michael Maines | | #7

    I've always worked where either rain or snow and cold are concerns, so I prioritize getting the house dried in--i.e., roof sheathing and a WRB--on as quickly as I can. Then I go back and frame up any interior walls.

  6. plumb_bob | | #8

    Mould will only grow on wood that has a moisture content of 19% or higher. So get the roof on and start the drying process with fans etc.

    Once the moisture content of the wood has dropped the mould will not continue to grow, but you will have to deal with the existing mould. Perhaps insurance can cover this remediation?

    After the remediation, a good poly air barrier that is installed with attention to detail should separate the living spaces of your house from the inside of the walls. Also consider the extra few steps to achieve air tight drywall. Good luck!

    1. andy_ | | #9

      Since you put a u in mold and recommend "a good poly air barrier", can we assume you're in Canada?
      We generally don't use poly down here south of the border, but I think your idea is that the living space be air separated from the wall cavities because of the mold?
      While not a bad instinct, I really don't think it's needed here. A simple cleanup once the house is dried in will take care of the problem. The framing lumber won't be that wet again so there won't be any mold growth once the house is dried in, and thus no need to separate it.

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