This page will give you an overview of all the components you'll need for the successful insulation of your roof.

Our UdiTOP wood fibre insulation system is a great way to insulate your roof and is done by laying the insulation boards on top of and between the rafters. It combines high levels of insulation with very high thermal mass and very good acoustic insulation. Alternatively, you can insulate from inside using the UdiFLEX wood fibre insulation system between the rafters.

REFURBISHING EXISTING

You’ll need to decide which thickness of UdiTOP board and this will depend on your target U-value. If you need to use a thicker layer than 120mm, add a layer of UdiTHERM square edge wood fibre board to the rafter first and lay the UdiTOP boards over the top before counter battening. If you’re refurbishing an existing roof you’ll need to balance the thickness required with any limitations such as parapet heights, junctions with adjacent structures and any planning restrictions.

For board thicknesses up to 52mm, assume each board will cover around 1.4m2 with 5% waste. From 60 - 120mm thicknesses each board covers around 1m2 with the same allowance for waste, so calculate the number you need accordingly. These coverage rates should be enough for simple single/dual pitch roofs but as soon as hips, valleys or dormers are added then you’ll need to increase the amount of waste in the calculation.

You'll need to know the meterage of all of the cut joints on the roof, such as ridges, valleys, hips and dormers. These need to be taped with UdiSTEAM Alubutyl tape to prevent rain water from entering the roof. Each roll is 10m long and will require UdiSTEAM Primer to be applied to the surface of the boards before applying the tape.

NUMBER OF FIXINGS

The UdiTOP wood fibre sarking boards are laid on to the top of the rafters and are held in place with counter battens. You’ll need to allow for screws that are long enough to go through the counter battens, the UdiTOP boards and around 40mm into the rafters. You’ll normally need around 4 per metre of rafter/counter batten but please call us to discuss further if you have any queries.

INSULATING BETWEEN RAFTERS 

The UdiFLEX flexible wood fibre insulation fits between the rafters and should FULLY fill the depth of the rafter. If you have slightly variable or odd sized rafters size the UdiFLEX a little thicker. E.g 150mm for a 145mm rafter. Check pack sizes as coverage varies depending on thickness.

When calculating the quantities of UdiFLEX insulation to go between rafters don’t forget to remove the space occupied by the rafters. E.g. 50m2 of roof may only need 45m2 of UdiFLEX insulation.

THE UNDERSIDE OF THE ROOF

The underside of any insulated roof needs to have a vapour control layer and airtightness layer included in it. This can be in the form of OSB or it can be a VCL membrane such as UdiSTEAM 10 plus. If you’re using OSB then use the UdiSTEAM Elastoflex airtightness tape to tape all of the joins in the boards and allow 3-4m of tape per m2 of boarding. If you’re using the UdiSTEAM 10 plus membrane then each 75m2 roll should cover 70m2 of roof (with the 100mm laps between rows) and joins should be taped with the UdiSTEAM Elastoflex tape.

INSULATING FROM INSIDE

If you have an existing roof with a breathable membrane installed then the insulation can be applied from inside. UdiFLEX flexible wood fibre insulation can be fitted between the rafters from underneath, fully filling the depth of the rafter.

To add additional insulation you can use a layer of UdiTHERM before fitting the UdiSTEAM variable VCL membrane and counter battens. Alternatively, you can fix the UdiUnger-Diffutherm boards or the UdiSPEED boards to the underside of the rafters and plaster as for Internal Wall Insulation.

If you have any questions, contact us.

 

Wood Fibre Insulation Sarking Boards - UdiTOP - Back to Earth
Wood Fibre Insulation Sarking Boards - UdiTOP from £11.33
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Square edge wood fibre insulation boards - UdiTHERM SK - backtoearthsupplies
Square edge wood fibre insulation boards - UdiTHERM SK from £3.53
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Thermal and acoustic flexible wood fibre wool insulation - UdiFLEX - backtoearthsupplies
Thermal and acoustic flexible wood fibre wool insulation - UdiFLEX from £23.28
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Breathable roofing underlay - UdiSTEAM Tex 155 - backtoearthsupplies
Breathable roofing underlay - UdiSTEAM Tex 155 £126.75
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Variable vapour control layer and airtightness membrane - UdiSTEAM 10 plus - backtoearthsupplies
Variable vapour control layer and airtightness membrane - UdiSTEAM 10 plus £165.08
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Air tightness tape for membranes (60mm) - UdiSTEAM Tex - backtoearthsupplies
Air tightness tape for membranes (60mm) - UdiSTEAM Tex from £16.45
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Flexible air tightness tape - UdiSTEAM Elastoflex - backtoearthsupplies
Flexible air tightness tape - UdiSTEAM Elastoflex from £15.83
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Air tightness tape - UdiSTEAM Alubutyl - backtoearthsupplies
Air tightness tape - UdiSTEAM Alubutyl from £19.98
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Primer for air tightness tapes (1kg) - UdiSTEAM - backtoearthsupplies
Primer for air tightness tapes (1kg) - UdiSTEAM from £13.73
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Air tightness collars - UdiSTEAM - backtoearthsupplies
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Air tightness collars - UdiSTEAM from £3.50
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Solvent free sealant - UdiSTEAM Fix - backtoearthsupplies
Solvent free sealant - UdiSTEAM Fix from £7.65
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