How To Insulate A Flat Roof From The Inside

There is a no attic space.

How to insulate a flat roof from the inside.

The type that is right for your flat roof insulation job depends upon the state of the roof expert opinion on the best type and your budget. This is then covered with a further weatherproofing layer. Insulation is placed in between the joists underneath the roof surface above. I have a 1948 building in south central pa with a flat rubber membrane roof.

Cold roof systems are highly inadvisable as insulation from the inside will inevitably lead to the formation of condensation. Roof types the various types of roofs found on homes sheds garages and other buildings fall into one of the following categories. The roof sheathing is directly on top of the joists. The joists are 2x12 with existing fiberglass batts installed between them.

Gable roofs hip roofs intersecting roofs butterfly roofs mansard. They lose loads of heat and are prone to leaking causing the materials to deteriorate. Not cheap but needs to be done right either way. To produce a hot roof rigid insulation is fitted outside above the weatherproofing.

The correct method for a flat roof is under the current regulations to have a warm roof. I am going to be lathing out the ceilings and hanging new drywall to cover up existing plaster damage and provide easy access for electrical contractors to. Framing this out and buying 30 r fiberglass insulation will cost you about 50 more than just buying 5 inches of polyiso equivalent of 30 r. Or insulate partially on the exterior side of the roof sheathing with an air control layer insulate in the rafters bays control the vapor diffusion and re work the fascia soffit etc.

In a nutshell you would sandwich 130mm of solid insulation between two decks allowing to place a vapour barrier on top of the first deck. Cold roof a very bad idea. It should be installed on tapered 2x furring strips in order to slope the surface of the roof to drains. Warm deck flat roof insulation is now the standard way to insulate a flat roof click to enlarge flat roofs for example on extensions bathrooms and dormer windows are not the best of ideas.

Flat concrete roofs are generally not ventilated since the ceiling internally is generally a plaster and skim coat directly to the underside of the cold concrete.