Design Requirements

design_requirements roof

1. Loft Hatches

The type and position of the loft hatch should be considered. Air sealed and insulated loft hatches are readily available and should be used. Avoid positioning loft hatches in or adjacent to high moisture areas such as bathrooms.

2. Close the Cavities

Heavy rain can saturate a brick wall with gallons of water. As the wall dries the vapour will also rise up through the cavity and thus enter into the roof space over the wall plate. The top of this cavity must be sealed to stop this excess vapour form entering the roof space. This can be simply done such as by extending the UPVC soffit across to meet the insulation.

3. Recessed Lighting

Open spotlights, such as in the bathroom ceiling, can allow large amounts of vapour to enter the roof space. In all cases only contained or sealed recessed lighting units should be used.

4. Thermal Bridge

Modern insulation to the ceiling and walls is well detailed. The junction of the ceiling and wall is often only a gap that is in the region of 80mm high. If the free movement of air is required then this means that this junction will be under insulated. Together with the movement of cold air over the wall plate and through this point then a cold (or Thermal) bridge will form. A thermal bridge will cause severe condensation and mould growth and is not allowed under the building regulations. The thermal bridge can be often noticed as mildew that forms at the front ceiling corner in the bedroom or at the sides of the window. Good insulation detailing is essential to avoid the thermal bridge.

5. Eaves Guard

As the moisture passes through the breather membrane it would then condensate on the underside of a cold tile. This condensation would then drip back on to membrane and run down to the eaves. Without an eaves support tray (tilting fillet) the membrane sags behind the fascia board and the water will pond and leak through the vertical laps etc and cause damage. Although Permavent has special U.V additives its exposure to the sun should be kept to a minimum and Permavent should not be draped into the gutter. The leading edge of the membrane should be stuck to the to the eaves tray just above the fascia line using 'Permavent'.

Water Tanks

It is essential that cold water storage tanks that are positioned in the roof space have a sealed lid. The roof will get very hot during the summer and would constantly evaporate the water in an open tank.



Following the success of the Queen’s award winning Easy Verge, here at Permavent we are proud to announce the launch of the recently developed Easy VergeTrim. This latest addition to the Easy Roof System has been specially designed to meet the requirements of the Scottish and refurbishment markets.

We use cookies to improve our website and your experience when using it. Cookies used for the essential operation of the site have already been set. To find out more about the cookies we use and how to delete them, see our privacy policy.

I accept cookies from this site.
EU Cookie Directive plugin by www.channeldigital.co.uk