Upgrading insulation on a refurbishment roof

Building regulations

Building Regulations state that when refurbishing or replacing an existing flat roof covering, the replacement system must also make provision for an upgrade to the thermal properties of the roof. Bauder can advise on the latest Building Regulation requirements, and make provision for the correct amount of insulation for your project within the bespoke specification that we provide. However, we would recommend that you seek confirmation of our advice from Local Authority Building Control before submitting the specification for tender.

Cold roof construction

If the refurbishment project in question is a cold roof design, upgrading the insulation in the ceiling void is often difficult as it will be necessary to remove either the ceiling or the roof deck in order to achieve this. Once exposed, it may be discovered that the existing void is too small to take the volume of insulation required whilst continuing to maintain an adequate cross flow of ventilation above it. Even if it is possible to upgrade the insulation in the ceiling void, it will be impossible to provide a continuous uniform thickness, due to the presence of structural supports. Therefore a certain amount of thermal bridging will occur.

It is often preferable to convert an existing cold roof to a warm roof construction, as this greatly reduces the problem of thermal bridging. However, this will mean that any existing ventilation provision below the deck will need to be sealed off and there may be a requirement to remove any existing insulation from the void, as this could cause condensation problems.

The Bauder Technical Department is always available to provide specialist advice or undertake thermal analysis calculations should this be required.

Warm roof construction

In the case of refurbishment of a warm roof, it is likely that the level of existing insulation will not be enough to satisfy current Building Regulations. There are commonly two options, either to overlay the roof and introduce additional insulation, or to strip the existing system and start again. The first option should only be considered if the existing roof is deemed suitable and compatible for an overlay.

Detail design

Particular attention should be paid to the design of the new roof system to ensure that thermal bridging at perimeters and details is reduced as much as possible. Guidance on detail design is given by ‘Accredited construction details’ which is available from www.planningportal.gov.uk

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