A Guide to the Repair of Historic Roofs - Dublin City Council

ROOFS A GUIDE TO THE REPAIR OF HISTORIC ROOFSDOWNPIPESDownpipes should be examined for defects, cleaneddown and appropriately refurbished. Replacementsections for broken lengths of downpipe shouldmatch the existing size and profile. Where downpipeshave been partly buried into walls by a coating ofrender they are liable to crack, discharging rainwaterback into the interior of the structure. Spacers shouldbe fitted to ensure that downpipes are properly heldoff the wall, so that if leaks occur the water hassufficient space to run down the back of the pipewithout saturating the wall. Where appropriate, fittinghinged downpipe brackets is very practical as itsimplifies the removal of downpipe for maintenanceor replacement.Cracked or broken rainwater goods can be replacedon a like-for-like basis with half round, box or ogeecast-iron gutter profiles which are readily available.Where castings are more decorative, such as in thiscase, new gutters can be cast to replace the brokensections. Downpipes should be carefully examined,cleaned down and fully refurbished on a regularbasisOverflow pipes can be fitted to hopper heads andcatch pits to alert owners of blockages. Where thegutters are hidden from view, such as secret or valleygutters, this is an especially useful early warningsystem and should be included when any major roofrepair works are undertaken.If there are deficiencies in the design of a rainwaterdisposal system it may, in some cases, be possible toreplace the existing rainwater goods with largersections in similar designs and profile. This may not beappropriate where the existing rainwater goods are ofarchitectural heritage value. Sometimes it may bepossible to increase the number of downpipes servinga roof or to add a new downpipe to a previously unservicedroof area. Depending on the location of theadditional outlet and downpipe, planning permissionmay be necessary for the modification and/or consentfrom adjoining property owners obtained.Some gutters, particularly those with a decorativeprofile, cannot be taken down for repair withoutremoving the lowest course of roof slate. Where suchgutters are cracked or have spots of corrosion, a metalinsert or continuous sleeve can be fitted into thegutter, to cover the faults. The chosen metal shouldnot cause galvanic corrosion. It should be fitted in dryconditions to avoid water being trapped between thetwo surfaces. This repair should suffice until a majorroofing job is undertaken and a permanent repair canbe achieved. For further information see Iron – therepair of wrought and cast ironwork in this AdviceSeries.Having made sure that the method of rainwaterdisposal from the roof is in working order, it isimportant to ensure that downpipes are properly ableto discharge into shores or gullies at the base of thebuilding. The base of the downpipe should notobstruct the grating or impede clearing of the gulley.An unusual example of a decorative cast-iron gutterdetail following the profile of a half-hipped roof71