Gutters & Slatework
Posted by Shaun Perry on Mar 10, 2011 in Building Surveying
The brackets that hold up cast iron gutters, or rhones, are known as rhone hooks. In Scottish roofing practice they are fixed to the sarking boards which in turn are fixed to the rafters. In England they have to be fixed to the rafters. The rhone hooks are galvanised steel and should be fitted before the slates go on. They need to be strong enough to carry the gutters but soft enough to bend so as to align the gutters. For many years now we have not had really heavy snow, at least not until this winter and the previous one so the strength of rhone hooks has not been put to the test and it is now pretty clear that the main suppliers of these vital components had taken the opportunity to compromise on quality. No doubt this was what their customers, the roofers, wanted because it made them cheaper and easier to use. It is, however, a foolish bit of cheese paring because when cast iron gutters fall down they invariably break or crack and even if they don’t actually fall off, but distort and the joints start to leak. Furthermore, in Scottish roofing practice the bottom course of slates is usually double nailed so it is a bother to change the rhone hooks. It is important to have enough rhone hooks. They should be spaced at about 600mm intervals or less.
Cast iron gutters are usually either half (or part) round or alternatively ogee profiled. The ogee style of gutter has a flat bottom and flat back and often sits on a stone ledge or on top of the wall but sometimes it is attached to the face of the wall with screws through the back. The recent weather has in many cases tested these fixings to destruction. Where ogee gutters sit on stonework it can be very difficult to detect a leaking joint. For this reason we like to fit them on top of a cloak of lead so that, if they do ever leak, the water does not soak into the wall where it invariably sets up fungal decay in built in timbers.
Other options for eaves gutters include uPVC which generally need to be fixed to fascia boards. These spoil the look of a building not designed for them. We try to steer away from uPVC. Contrary to popular belief it does not last all that long and it creates an environmental problem at the end of its life. Traditionally lead was often used for gutters with copper rods wrapped into its edges to provide rigidity. This is a very expensive form of guttering but good quality existing lead gutters should not be lightly discarded as they should be repairable. Zinc was also commonly used in the past but Victorian zinc gutters are usually corroded by now.
Other modern guttering systems include the attractive and durable Scandinavian Lindab metal gutter system. Lindab gutter brackets need some muscular adaptation to make them suitable for use on a Scottish roof where the slates are fixed to sarking boards. Then there are various site formed aluminium guttering systems which look fairly good but are very lightweight and easily damaged. Sheet aluminium is put through a roller which creates the profile and they can be jointless except at corners.
Scotch single nailed slated roofs are relatively easy to repair. Most repairs are completely invisible. However double nailed slate roofs are less easy to repair because invariably the slates have to be ripped out and un less they are at the top of the roof they can’t be renailed with two good nails. Roofers who are obliged to undertake an invisible repair in these circumstances invariably resort to using high grab adhesive and glue replacement slates to their neighbours. A better answer is to use a visible fixing called a tingle although often the metal strip used for this purpose is not strong enough to do a good job. Some roofing component manufacturers now make black plastic adjustable tingles which have the merit of not looking too obvious.
When it comes to repairs and maintenance the great difficulty that faces every owner of a slated roof is safe access. What seems like just a few years ago roofers were happy to clamber around on roofs without any form of harness, edge protection or scaffolding. This practice has been outlawed. The options are limited.
Scaffolding is often proposed as the only option but in many cases there is another: it is known as “Rope Access” and it has its own set of very safety conscious rules and trade association. Safe working practices developed for bridges, oil rigs and industrial plant can be applied to buildings and this is sometimes a more economical option that the conventional alternatives. Health and Safety experts remind us that harnesses are not, on their own, a panacea. It is important to get an operative who has been left dangling on a rope, quickly to the ground because experience has shown that any longer than about 20 minutes is life threatening. In many situations it could take longer than this to rescue the dangling operative.