How To Insulate A Flat Roof Externally

You would only do this however if replacing the roof covering on top and you have the height above the roof to do this.

How to insulate a flat roof externally.

Like other roofs insulating a flat one requires ample ventilation a vapor barrier and sealed bypasses. It also lets hot air escape in the summer. The correct method for a flat roof is under the current regulations to have a warm roof. Then install r 30 fiberglass batts between the rafters.

Insulation is placed in between the joists underneath the roof surface above. It should be of the maximum available thickness. Add an additional layer of osb over the sheathing. When a homeowner really needs to cut down on costs some contractors may suggest the following.

To achieve this add 100 to 160mm of insulation above the structural deck dependant upon insulant conductivity. With a warm roof the usual process is to split the insulation into two layers. If 180mm is to be installed then 100mm board might be introduced between the rafters there has to be a minimum 25mm air gap between the insulation and the underside of the tiles or slates with an 80mm board running across the rafters. It should be installed on tapered 2x furring strips in order to slope the surface of the roof to drains.

The typical u value of an existing uninsulated flat roof is 1 5w m2k. 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. Insulation material is placed on top of the roof rather than in between the ceiling and the decking. The material that works best depends largely upon preference in a given situation.

Ventilation is necessary to allow moisture accumulated inside to escape. Proper ventilation in flat roofs.