Celotex Isover

Insulation for Beam and Block Floors

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Compared to the wet trades involved when insulating above or below a concrete slab, suspended concrete floors offer a fast, effective, dry operation. The floor can be a beam and block (also called block and beam, or pot and beam) deck or, on larger projects, a precast concrete plank craned into position.

Suitable for use on projects where a concrete slab might ordinarily be used, suspended concrete decks are particularly desirable where there is unstable ground, a high water table, or too much poor soil needs removing. They also make it easier to provide a level floor on sites with an excessive slope.

A concrete deck is not at risk of rot like the joists in a suspended timber ground floor, but the sub-floor void must still be ventilated to prevent any potential build-up of gas.

In a block and beam deck, concrete blocks are laid between, and supported by, concrete beams shaped like an inverted ‘T’. The lighter the block, the greater its contribution to the thermal performance of the floor; it’s also possible to use infill blocks made from expanded polystyrene insulation.

Installing thermal insulation below a concrete deck is not usually an option, so rigid insulation is installed on above the deck. Lightweight, rigid polyisocyanurate (PIR) foam insulation boards, such as those manufactured by Celotex, are among the most thermally efficient, commonly available insulation materials. They keep the depth of the floor construction down, and are easily handled and laid to quickly insulate large areas.

With an appropriate separation layer installed over, such as light-gauge polythene, they are then easily covered by a concrete screed or tongue and groove chipboard, ready to receive the specified floor finish.

The building detail is for illustrative purposes only. It does not constitute advice and should not be relied upon.


Insulation products to consider
Product Name Thickness Range Sizes Lambda BBA
Celotex XR4000 110-200mm Width 1200mm, Length 2400mm 0.022 W/m.K Tick Icon
Celotex GA4000 50-100mm Width 1200mm, Length 2400mm 0.022 W/m.K Tick Icon
Celotex TB4000 20-40mm Width 1200mm, Length 2400mm 0.022 W/m.K Tick Icon