Flat Roof Insulation

Glass faced PIR boards
Mineral wool slabs
PIR boards with plywood
Warm deck insulation
For single ply or built-up

KNAUF, ROCKWOOL, CELOTEX, XTRATHERM, CELLECTA

The type of insulation used in a new flat roof is dependent on the roof specification. On a new concrete slab, with a screed, semi-rigid insulation boards such as expanded polystyrene board, extruded polystyrene board, glass fibre batts, mineral fibre batts, urethane foam board or phenolic foam board are laid under the roof covering. In a new timber structure, glass fibre quilt and mineral fibre quilt can be laid between the joists. In case of an existing flat roof, insulation can be increased externally with extruded polystyrene or foamed glass, or internally with an insulated lining board such as mineral fibre or polyurethane foambacked plaster-board.

Three choices are available for insulating a flat roof depending on the roof specification:

Cold roof
Warm roof
inverted roof

It is essential to understand the difference between those specifications to be able to install insulation in the right place to create a vapour barrier in the right area and prevent rotting of the roof joists.

Warm roof

A warm roof is when the insulation spans across the top of all the joists; it must be continuous and span over every joist. This means that any air rising from underneath would make the void between the joists warm hence a warm roof.

Cold roof

In a cold roof the insulation is put at the bottom of the joists or below the joists. This way sufficient ventilation is maintained which allows air to circulate above the insulation (below the roof). The void above the insulation should be at least 50mm thick. In this case the decking with the roof on it, which is above the joists, would be cold hence a cold roof.

Common mistake in the roof specification is when the insulation is installed inside the joists (close to the top part of the joists). This makes the roof neither cold nor warm, creating the void below the insulation. In this case there is no ventilation which makes the whole roof sweat and causes the joists to rot.

Inverted roof

The inverted roof concept which is also known as protected membrane or upside down roofing. This method ensures insulating both the water proofing membrane and the reinforced concrete slab from extreme thermal stress. This is achieved by placing an extruded polystyrene thermal insulation board above, instead of below the waterproofing membrane and can be used for insulating flat topped buildings or balconies, retail or office developments, flats, hospitals, airports, hotels and residential housing in areas where roof is exposed to high temperatures.

Insulationshop.co offers a wide range of high density flat roof insulation from manufacturers such as Xtratherm, Celotex, Knauf, Kay Metzeler, Cellecta and more. For more information about particular products please see product description.

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59mm Plydeck Xtratherm (PIR with OSB Board)

2400x1200 - 2.88m2 show quantity discountsDelivery Time: 1 - 2 days

Guide Price: £70.01 (£84.01 inc VAT)

£24.31/m² (£29.17/m² inc VAT)

show quantity discounts

A10-179

Due to nationwide shortage of PIR insulation lead time may be longer for this product.

Xtratherm Plydeck is a composite insulated panel of Xtratherm Polyisocyanurate core with a composite foil face, bonded to 9mm OSB board. The Xtratherm Plydeck provides a high level of thermal insulation and decking in one application.APPLICATIONPlydeck is designed to provide high levels of thermal i..

Guide Price: £70.01 (£84.01 inc VAT)

£24.31/m² (£29.17/m² inc VAT)

show quantity discounts

A10-179

= m²

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Flat Roof Insulation

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