In my professional life as a Technical Officer for the Lead Sheet Association I often get asked what is the correct way to fit a lead gutter.
Should they be fitted in the traditional way with drips (steps) breaking up the lengths or can rubber expansion joints be used?
Example of a typical box gutter
My answer is always if it can be done the traditional way then go for it. Obviously if you find yourself in a situation when it can’t you may have no choice other than to use an alternative.
So what is a rubber expansion joint and when should you use it?
The answer lies in its history to a degree. Neoprene expansion joints, to give them their proper name, first found their use in Europe and were used in conjunction with zinc and copper gutter linings. The idea being that a method of jointing was needed to take into account the thermal expansion of certain types of metals. Traditional methods for jointing copper gutters, again with steps along its length, could not be easily replicated in zinc as the material was not as malleable.
In the early 1990s the same principle was introduced in the world of leadwork. The reason for this was that traditional wall head gutters that were made from concrete and lined with lead, which can be found on many older buildings up and down the country, needed the leadwork replaced. In the old days the lead lining pieces were just lapped and water ingress was inevitable. As it was impossible to create the traditional steps in these installations, neoprene expansion joints were seen as a good solution.
Over the years these types of joints have been applied in many different gutter situations and appear to be giving a good service life to date. Their popularity has grown given that they can be welded into place much faster than using traditional ‘bossing’ methods to form the drips.
Why is that a problem you might ask?
One of the main reasons that we refer to these as a ‘last resort’ is that they only carry a manufacturers guarantee of 5 to 10 years. When we talk about lead it is expected that it should give a service life in excess of 60 – 100 years.
Having a component within this that may have a shorter lifespan is an obvious weak point and one we would prefer is avoided if possible. Certainly we would like their use restricted to places where there is no choice. Using these may restrict any insurance backed guarantees and could, in certain circumstances, lead to costly replacement works which would require full scaffold access.
At the end of the day all leadworks should take into account the anticipated life of the building concerned. Where a lesser service life may be acceptable to a building owner or developer the use of neoprene expansion joints could be considered. By contrast, where maximum service life is required standard traditional details should always be used. If you are using the neoprene joints this should be discussed with the client and perhaps have it built into any maintenance programme.
All the details used here are from the LSA's,
Complete Manual, which has just recently been updated and includes a wealth of detail on the installation and specification of this amazing building material. We also provide further information and technical support on our website www.leadsheet.co.uk.
By Darren Tutt, Senior Technical Officer.
The Lead Sheet Association
NB any detailing provided by the Lead Sheet Association refers to the use of Rolled Lead Sheet to BS EN 12588.
Please Note: Every care was taken to ensure the information in this article was correct at the time of publication. Any written guidance provided does not replace the reader’s professional judgement and any construction project should comply with the relevant Building Regulations or applicable technical standards. However, for the most up to date LABC Warranty technical guidance please refer to your Risk Management Surveyor and the latest version of the LABC Warranty technical manual.