Stark warning over new green roof for Town Hall

Published: 3:36 PM July 22, 2009

Updated: 1:26 PM October 14, 2020

I was very interested to read the article (Town Hall first to go green on top, H&H July 16). Whilst I support this idea I have the following reservations which Cllr Alexis Rowell appears to have overlooked and does not seem to have highlighted to other i

I was very interested to read the article (Town Hall first to go green on top, H&H July 16). Whilst I support this idea I have the following reservations which Cllr Alexis Rowell appears to have overlooked and does not seem to have highlighted to other individuals who may wish to carry out this work.

The introduction of a green roof could substantially increase the load on an existing roof. It is therefore essential that the roof and supporting structure are checked to ensure that they can support this additional load.

By introducing a green roof, the height above the existing finished roof is increased which may reduce the recommended height for the asphalt upstand (this is evident from the photograph accompanying the article) and this in turn increases the risk of water ingress.

A green roof will retain a higher level of water and moisture which can seep into the building below. Furthermore there is a higher risk of condensation in the building. Anyone considering a green roof should be taking professional advice on all of these issues. I am assuming that Camden Council did this too.

Cllr Rowell also says that he wants this roof, along with some exemplary green roofs, to be open to the public. Public access to a roof will also impose a greater load on that roof. So again professional advice has to be taken beforehand to ensure sufficient structural support for increased roof load.

So in addition to planning, there are other issues, some of which I have highlighted above, which have to be dealt with before introducing a green roof.