Breathable Roof Membranes

• Roof underlay for both warm and cold pitched roofs

• CE certified quality product

• Provides a barrier to wind driven rain, snow and dust into the roof void

• Excellent waterproofing characteristics

• High water vapour permeability

• Membrane is lightweight, strong and easy to handle and install

• UV stabilised and has an increased flammability resistance

Product Literature Downloads

Strotex Extra (E115) 115gsm - 1 x 15m, 1 x 50m & 1.5 x 50m

Strotex Super (S125) 125gsm 1 x 50m & 1.5 x 50m



Strotex is designed to be installed coloured side up. Tiling battens and where required counter battens, should be fixed to allow the product to drape between the rafters more than 6mm but not less than 25mm to allow any moisture to run off. The membrane should be installed horizontally starting at the eaves. Further rows of membrane should be lapped both vertically and horizontally as below.

Strotex Supreme 170gsm 1 x 50m & 1.5 x 50m

Strotex Performance 220gsm 1 x 50m & 1.5 x 50m

Dedicated To Supporting Builder's Merchants

Download BBA Certificates

Sheet 1 -   For use in warm non-ventilated and cold ventilated roofs

Sheet 2 -   For use in cold non-ventilated roofs

Permeable Roof Tile Underlay - Guide to Good Site Practice

Sheet 3 -   For use in Timber Frame Constructions

Ensure any penetrations such as roof lights, chimneys and service pipes are dressed to a minimum of 100mm to the up stand and sealed with flashing tape

Valleys and Hips must be covered with a separate 600mm wide strip of membrane

Strotex should be returned up any abutment by 75mm from below a proprietary lead or alternative flashing


Strotex must be lapped over the outer walling by at least 75mm at verges. Where there is a constructed overhang the product must be fixed to the outer rafter.


Where a duo roof is to be covered overlap the membrane by 150mm from one elevation to the other. For mono roof ridges the product should be extended over the ridge by 100mm. The membrane should also be extended to protect to the ends of roof timbers.


Strotex Breather Membrane should be supported by Rhinovent Eaves Guard at the eaves and draped a minimum of 150mm onto the guard. The eaves guard should be extended beyond the outer fascia board so that moisture may drain into the gutter.

Rhinovent Eaves Guard is obtainable from Principal Building Products.


Download BBA information Bulletin



The British standard for the installation of underlays in roofs is the British Standard for the Control of Condensation in Buildings; BS 5250:2002 This is referenced in relevant sections of the Building Regulations in England and Wales, (Approved Document c). Scotland (standard 3.15) and Northern Ireland (Technical Booklet c). An amended version of BS 5250:2002 was issued in December 2005 and these should now be followed.




Although Strotex has a high UV resistance it is specifically recommended to cover the membrane as soon as possible with permanent roof tiles.




BS 5250:2002 states there must be an adequate flow of air through the batten space when a breather membrane is used in a warm roof application. With most roof tiles and slates these provide enough ventilation but if an airtight tile or slate is used batten space ventilators should be installed. Counter battens will not normally be needed when the membrane is laid unsupported with drapes but counter battens will be

required when the membrane is fully supported on insulation.




In order to work effectively it is important that breather membranes are laid so that the space between the membrane and roof covering allows for adequate ventilation. Tiling battens should therefore be at least 25mm thick to ensure an adequate airspace between the membrane and final roof covering to allow water vapour to disperse. Counter battens are not normally required in a non ventilated cold roof as there should be adequate airflow between roof tiles or slates. However if an unusually airtight final roof covering is used then batten space ventilators and counter battens should be used.


Ref: BS 5250:2002

The final roof covering manufacturer’s advice should be sought on their products air openness when installed.  In non ventilated cold roofs consideration must be given to providing a vapour control layer and vapour check plasterboards to maintain a convection tight ceiling. All penetrations will require sealing including any loft hatches. The building below the roof void should be ventilated in accordance with national building regulations and standards. Extractor fans should be used in rooms with above average humidity and all water tanks should be covered and pipes lagged in the roof void. Advice should always be sought from Local Authority Building Control on the design and installation of ventilation systems with particular regard to cold roofs.


Contact Information


Address: Barbot Hall Industrial Estate, Mangham Road, Rotherham, S61 4RJ

Phone: 01709 728150



01709 724975



Sales Fax No:





  • Terms & Conditions

Facebook Page

  • Modern Slavery Statement
  • REACH Regulations for PU products