how to add a false roof ??

18 years ago

Looking for your great help with this, folks! We have a small lakeside cottage... one-story ranch-style with cathedral ceilings inside throughout. We need to add insulation to the ceilings/roof because it gets unbearably hot in summers (most of house faces directly west on the lake, with no opp for shade trees, unfortunately). We love the look of the natural pine T&G ceilings - and don't want to add the insulation inside - so we're thinking we need to add a 'false roof' on top of the existing roof?? Anyone have exp with this? Any cautions? What type of insulation should we use? should the existing asphalt shingles rbe removed first? Thanks for any/all advice!!

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Comments (5)

che1sea
18 years ago
Well I am not sure about all of it but I would definitely remove the shingles first.
greg_h
18 years ago
We did this exact thing on my sister's cottage.

I wasn't the brains behind the operation (I was just cheap labour), so I don't know all of the correct terms. But here is what we did:

(1) Remove the old shingles.
(2) Add a layer of rigid styrofoam. I'm not sure what kind of styrofoam it was but it had some kind of paper-thin layer of fiberglass stuff on it. All I remember is that it was a little itchy.
(3) Tape the joints with that tape that you use on vapour barriers.
(4) Lay 2x4s flat from eaves to peak, using screws that are long enough to go through the styrofoam and into the original roof.
Space the 2x4s every 2 feet.
(5) Lay plywood on top of the 2x4s. Stagger the joints.
(6) Add soffit vents and a ridge vent.
(7) Lay shingles.

The idea is that there is a path for air to travel from the soffits to the ridge vent in between the styrofoam and the plywood to remove the heat generated by the sun on the roof.

Made a huge difference in the temperature.
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yellowpups
Original Author
18 years ago
Thanks for the info! GregH, when you say "4) Lay 2x4s flat from eaves to peak, using screws that are long enough to go through the styrofoam and into the original roof." ...did you actaually screw into the existing roof sheathing? Problem with ours is that the ceiling tongue & groove IS the roof!? We don't want to screw/nail into that. Could it be that there is an additional sheathing on top of the T&G ?
greg_h
18 years ago
My sister's cottage is basically constructed out of tongue and groove 2x4s. No rafters, no studs in the walls. I've never seen this type of construction before. So the roof sheathing was actually 2 inches thick. Plenty of room for the screws to bite into without poking through.
Do you have rafters that the 'new' 2x4s could be screwed into? They would be spaced the same distance apart as the new 2x4s would be.
greg_h
18 years ago
I should probably also add that my sister's cottage has a fairly low sloping roof. That might have some bearing on how securely things had to be attached. I can imagine that if the roof was steep, then the 'new' roof would have had to have been attached 'better' to keep it from essentially sliding off.
As I said before, I wasn't the brains of the operation. My family knows a GC that works on cottages on the lake that basically told us what we had to do, given our specific cottage construction. YMMV