A reader's Roofs and roofing question: Condensation problem?

Rebecca P.   from   CLEVELAND : United States   had this Condensation problem question.

Bill's answer

Hi Rebbecca,
It sounds like the roof was put on without any foil underlay. If you look on a few of my roof pages you will see what I mean, it is the shiny stuff.
The best photo is on the insulation page.

• I have actually put this stuff under roof sheeting from the inside, and it was a real hard job to do. This was on a house that had a reasonable roof pitch and the rafters were at 3ft centers.
• Yours could be a lot less and I wouldn't advise you to try this way.
• I have not heard about it, but maybe you could find someone to spray a foam type insulation product to the underside of the sheets.
• I am thinking of the stuff that you see on auto body panels to deaden sound. Could be very expensive though.
• I don't like the idea of one roof over the other, and any spray seal on top of the roof surface won't address the problem of condensation under the sheets.
• If your roof iron is still in good condition I would lift it off and put the insulation foil under it, then replace the same sheets.
• I really depends on how the roof iron is fixed. If it is fixed with screws, no problem, an average home handyman could do it.
• Take off the ridge or hip flashing to a section. (using a good roofing screw gun).
• Take off two or three sheets only and fix the new foil from ridge to the fascia, taping the joint neatly and leaving overlap at the ridge and fascia.
• Fix the sheets back again in the same order they came off and into the same screw holes.
• Repeat this for as long as the session lasts, and then temporarily fix the flashings back on until the next session.
• Doing it this way you split the job up into small sections that could be done at weekends etc. but with the place always weather proof.
• Depending on how old the roof is I would consider using new screws and seals, because the seals get hard over time.
• Doing a small section at a time is less risk for bad weather, and it is easy to take your time and do a good job with the foil, because you have something to stand on at either side.
• If the iron is fixed with nails then it could be harder, as removing the nails tends to damage the sheets.
• If the iron is old anyway, then I would fix new roof sheeting the same way.