Advice & Guidance
Repair or Replace
Dealing with the repair or replacement of rainwater goods can be a fraught subject. The general principle is that it is better to repair than to replace where possible, although this not always a straightforward issue.
Cast iron
Cast iron is one of the most common materials used for rainwater goods on historic buildings. The material is robust and will last for a long time if it is well looked after.
It is, however, vulnerable to cracking and to corrosion if it is not maintained properly. Cracked or split sections of cast iron can sometimes be repaired though this requires considerable skill and expertise as welding can be problematic. The integrity of such repairs cannot always be guaranteed.
If repair is not feasible and you do have to replace parts of your cast iron rainwater disposal system make sure that they match the originals in terms of size and appearance as undersized replacement gutters and downpipes can lead to overflows and leaks.
Plain or simple castings can often be obtained from a local builders' merchant whilst ornamental or unusual castings can be sourced from the small number of foundries still specialising in traditional casting techniques.
If you do opt for replacement you might consider increasing the capacity of the rainwater disposal system by increasing the size of gutters, hoppers and downpipes.
You might also think about increasing the number of downpipes and adding an overflow detail if appropriate.
This may help your building cope better during the increasingly heavy and sustained spells of rainfall experienced in recent years but do remember that you may need to seek permission for any changes.
If possible, consider fixing new downpipes with a gap between them and the wall to facilitate repainting the rear faces in the future. This will also allow any leaking water to run down the back of the pipe rather than down the wall.
Once your rainwater disposal system has been returned to full working order the best way to look after it is to make sure that you keep the components in good condition with frequent repainting. Expect to repaint once every five years although they may need more frequent attention in coastal or exposed areas. Your architect or building surveyor will be able to prepare a detailed specification and can advise on suitable local contractors.
Alternative materials
Even though it may be tempting to replace cast iron rainwater goods with less costly options such as extruded or pressed aluminium, mild steel or plastic sections this is not advisable as such materials detract from the traditional character and appearance of the building.
Whilst
the alternatives are
cheaper to purchase and install, any saving must also be balanced against the
need to
replace them on a more frequent basis. Good quality cast iron components should easily last 100 years if they are well maintained, whereas plastic rainwater goods may only last 10-15 years due to degradation and buckling caused by exposure to ultraviolet light. Extruded or pressed aluminium and mild steel may last for 30 years or more but this can depend on the choice and quality of the protective coating.
In some cases it may be acceptable to substitute cast iron with painted cast aluminium where access for redecoration is exceptionally awkward. Cast aluminium has the benefit that it requires very little maintenance but it is unlikely to be significantly cheaper than choosing cast iron. The life span of cast aluminium components may not be as great as cast iron either, so it is sensible to budget for their replacement after 40 years in rural areas and after 25 years in industrial or maritime environments.
Lead
Lead has been used for rainwater goods for many centuries - there is a reference to lead downpipes at the Tower of London in 1241. Generally speaking it is highly resistant to corrosion but it can deteriorate if affected by certain acidic or alkaline chemicals. More common problems arise from poor detailing, insufficient support, thermal stress, theft or mechanical damage.
Where lead rainwater goods have become damaged they can often be repaired and improvements made to correct technical faults if necessary. A skilled plumber can mend lead rainwater goods with techniques such as leadburning, welding or soldering. Distorted leadwork can also be gently eased back into shape if it is not performing its task but the temptation to correct functional but distorted leadwork should be resisted.
Further information
- Christopher Brereton (1995) The Repair of Historic Buildings: Advice on Principles and Methods. English Heritage
- British Research Establishment (1997) Good Repair Guide 9: Repairing and Replacing Rainwater Goods. BRE
- Peter Rumley (2007) Conservation of Decorative Leadwork, SPAB Technical Pamphlet 17
- Information about the embodied energy of the materials used to manufacture rainwater goods has been collated by Tuscan Foundry Products Ltd (NB the references to aluminium may relate to pressed rather than cast components.)
© SPAB 2010
