Insulating Existing Concrete Flat Roof

I ve built a timber frame to support a new plasterboard ceiling below the existing one.

Insulating existing concrete flat roof.

Cold roof a very bad idea. Achieving a u value of 0 20w m meaning your roof will be better insulated than your walls will need 120mm thickness of rigid foam or 200mm of mineral wool or natural insulation. Cold roof systems are highly inadvisable as insulation from the inside will inevitably lead to the formation of condensation. Roofing insulation is one of the most important and misunderstood building components.

Both these variants require different approaches to insulation which will be covered in this guide. I want to insulate below a flat roof without removing the existing ceiling. Insulation material is placed on top of the roof rather than in between the ceiling and the decking. This is then covered with a further weatherproofing layer.

Refurbishing an existing timber joisted flat roof which has no insulation. There are many different types and installation methods out there along with a lot misinformation about which products offer the greatest energy savings. With a flat roof this issue does not arise but the u value constraint and the amount of insulation needed is just the same. With an inverted warm roof construction put ballast usually graded pebbles or concrete paving slabs on top of the insulation in order to keep the insulation down in the event of wind.

How to insulate a flat roof. Green roofs a green sedum or grass roof can also be put onto a flat roof provided it can take the weight. To insulate a flat roof with a concrete deck we recommend a warm deck construction method where the vapour control layer is sandwiched between the concrete deck and a layer of rigid pir insulation boards. This method eliminates the need for ventilation and the risk of condensation whilst providing superior thermal performance to cold deck.

Roof types the various types of roofs found on homes sheds garages and other buildings fall into one of the following categories. This is used for refurbishment e g. To produce a hot roof rigid insulation is fitted outside above the weatherproofing. Gable roofs hip roofs intersecting roofs butterfly roofs mansard.

The insulation is below the deck but above the plasterboard. The existing ceiling is sound but provides no insulation. There is only a small gap between this ceiling and a concrete roof cold roof felt covered. A cold flat roof is one where the insulation is between or between and below the roof joists.