How To Insulate A Flat Roof Externally

Insulation is placed in between the joists underneath the roof surface above.

How to insulate a flat roof externally.

Add an additional layer of osb over the sheathing. Then install r 30 fiberglass batts between the rafters. 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. The correct method for a flat roof is under the current regulations to have a warm roof.

It also lets hot air escape in the summer. When a homeowner really needs to cut down on costs some contractors may suggest the following. 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. The target should be to achieve a u value of 0 25w m2k or better.

Ventilation is necessary to allow moisture accumulated inside to escape. The typical u value of an existing uninsulated flat roof is 1 5w m2k. Proper ventilation in flat roofs. The material that works best depends largely upon preference in a given situation.

You would only do this however if replacing the roof covering on top and you have the height above the roof to do this. Like other roofs insulating a flat one requires ample ventilation a vapor barrier and sealed bypasses. Creating a void between the old ceiling and new is better but ideally you need to eventually consider insulating the top of the concrete roof with solid insulation and a better covering grp or epdm. Insulation material is placed on top of the roof rather than in between the ceiling and the decking.

It should be installed on tapered 2x furring strips in order to slope the surface of the roof to drains. It should be of the maximum available thickness.