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

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ROOFS A GUIDE TO THE REPAIR OF HISTORIC ROOFSbuildings were built with the central valley made of acontinuous narrow cast-iron gutter, instead of themore usual copper or lead gutters formed betweeninternal roof slopes. Lead drainage downpipes weresometimes run within the walls of eighteenth-centurybuildings and are the cause of considerable damage ifthey fail.Cast-iron rainwater systems often copied thedesign of leadwork, but the stronger nature of castiron enabled the use of shallow collars and twopointfixings rather than the deep collars neededto support lead rainwater goodsDuring the nineteenth century, cast iron replaced leadas the most common material used for rainwatergoods. Gutters are held with wrought-iron or cast-ironbrackets while downpipes are fixed to masonry withcast-iron brackets. Eighteenth-century wrought-ironbrackets tend to be deep and curved with two fixingpoints while later brackets were simpler and weremade of both wrought and cast iron, usually with onefixing point or a spike end which was driven into themasonry at eaves level. The weight of iron guttersensures that they do not lift in severe weatherconditions. In the later Victorian period, hopper headsbecame more decorative and a feature of elevations.Rainwater downpipes and guttering of larger squareprofiles were used, no longer painted in lead grey orblack, but highlighted in greens or blues as part of theco-ordinated decoration of the structure.rainwater goods were formed out of lead sheet withlead outlets through parapets, valley gutters, or leadeaves, connecting to lead hopper heads anddownpipes. Lead box hopper heads and squaresectionlead downpipes can still be seen, some withthe building construction date embossed on thehopper head. Hopper heads were used to collect andchannel the water from the gutters into thedownpipes, since gravity drives the mass of waterdown the rainwater pipe much more effectively ifthere is a head of water.In terraced buildings, long lengths of lead-linedparapet gutters were used. These gutters were builtinto the space between roof and parapet and werelaid to a fall or gentle slope, sometimes steppingacross many building fronts to a common hopperhead and downpipe. Internal valleys were servicedwith a ‘secret gutter’ made of a timber box sectionlined with lead that directed rainwater through theattic space to a chute on an external wall. Some25
ROOFS A GUIDE TO THE REPAIR OF HISTORIC ROOFSGetting the right adviceWhen it comes to repairing a building, regardless of its age or size, it is important to know when specialistadvice is needed and where to find the right help. It is a false economy not to get the best advice before havingwork carried out. Bad repair works can be difficult and expensive to undo. They can damage a building inthe long term and devalue your property. In addition, the interpretation and application of the more technicalrecommendations in this guide should be entrusted to suitably qualified and competent persons.You will need the right advice for a particular job. Sometimes you will require a craftsman, or an architect, asurveyor or a structural engineer. Sometimes you will need specialist advice from someone with a particularexpertise, perhaps in slating techniques, structural timber repair or leadworking. At the outset, and particularlyif your building is a protected structure, you may need advice on whether the proposed works requireplanning permission or not. When undertaking a large or complex conservation and repair project, a multidisciplinaryteam may be required. Most importantly, you should ensure that any advisor is independent andobjective. Avoid taking advice from someone trying to sell you something, or someone with a vested interestin increasing the scale and expense of work. Many building professionals and contractors are principallyinvolved with modern construction and may not know how to deal sympathetically with an old building. Youneed someone who understands old buildings, has experience in dealing with them, and has trained to workwith them. He or she should be knowledgeable and have experience in dealing with your type of building.When employing a professional advisor or a building contractor, check their qualifications and status withthe relevant bodies and institutes. Ask for references, and for the locations and photographs of recent similarwork undertaken. Do not be afraid to follow up references and to visit other building projects. A good practitionerwill not mind you doing this. If you see a good job successfully completed on a building similar toyours, find out who did the work, whether they would be suitable for the works you want to undertake, and ifthe building owner was satisfied.Try to get at least three written estimates or quotations for the work from suitable contractors. Do not makeyour final choice based on cost alone. The cheapest quote you receive may be from a person who does notfully understand the complexity of the problem. Do not make payments for work until you are satisfied it hasbeen correctly completed.Be clear when briefing your advisor about what you want him or her to do. A good advisor should be able toundertake an inspection of your property, give you a report identifying the causes of damage, make a carefuldiagnosis of the problem, recommend repairs, specify the work required, get a firm price from a suitablebuilder or craftsman, and oversee the work on site as it progresses. If your building is likely to need ongoingworks over a number of years, your relationship with your advisor and builder will be important both to youand your building, and continuity will be a great advantage. They will be able to become familiar with theproperty, and to understand how it acts, and will build up expertise based on your particular building.The Royal Institute of the Architects of Ireland (RIAI) has an accreditation system for architects trained inbuilding conservation and can provide a list of those architects that are accredited. Similarly, the Society ofChartered Surveyors has a register of conservation surveyors. The Construction Industry Federation also has aregister of Heritage Contractors working in the field of building conservation. The architectural conservationofficer in your local authority can provide general advice and may be able to give advice on suitable professionals,craft workers and suppliers in your area.26
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