You can choose plastic gutters or steel gutters for roof drainage. It is also possible to make guttering of aluminium sheeting or use titanium-zinc gutters. What should I pay attention to when shopping?
It consists of gutters and downpipes, as well as drip pipes (a combination of gutter and downpipe), elbows, spouts, corners and mounting accessories – bottoms, hooks (gutters), clamps, fittings, gaskets. Manufacturers have all these items in their offer. It may be troublesome to buy non-standard corners – with an angle other than 90o, which will be needed, for example, on the roof of a multi-angle bay. It is worth checking how the prices of the whole system are calculated. Sometimes gutters and downpipes are cheap but complementary elements are very expensive. It may also happen that some elements are composed of several smaller ones and you have to pay for each of them separately. On the market, you can find gutters with half-round, square, rectangular and even profiled in the shape of a cornice. The most popular are guttering systems, where gutters and downpipes are bought in sections, and then the whole system is assembled on the roof. You can also buy drawn systems (made of aluminium). Here, the gutters are manufactured on the building site – they are pulled out of the machine to the required size.
Choose the size of gutters
To get the right size and number of gutters and downpipes, you must first measure the distances on the roof and determine the effective roof area (EPD). The formula to calculate this is: (1/2H + W).L, where H is the height of the roof slope measured vertically, W is the distance from the corner to the ridge measured horizontally, which is the horizontal projection of the rafter length, and L is the length of the roof. For roofs smaller than 50 m2 , 100 mm diameter gutters and 75-80 mm downpipes should be selected. On a roof of 50-100 m2, 125 mm diameter gutters and 90 mm pipes are used. Large roofs (over 100 m2) require drainage with gutters 150 or 190 mm in diameter and downpipes 110-120 mm. When the roof is very steep, the indicated dimensions should be increased accordingly. Please note that one pipe can carry water from the eaves up to 12 m in length.
Made of PVC. Their durability is estimated at 50 years. The system elements can be glued and pressed together or fixed with connectors. It is important to remember that plastics expand when exposed to very high temperatures and shrink when subjected to frost. The system must be dimensioned with a little play, so that it is not installed too rigidly, or it may crack in summer. A disadvantage of PVC is that it stiffens in the cold. Therefore, if icy snow stays in the gutters in winter, it may cause them to crumble.
Systems made of galvanised steel sheet with a polymer coating on both sides are much more durable. Pay attention to the thickness of the steel (0,5-0,7 mm) and the coating layers. The thicker they are, the better. Manufacturers use various protective coatings. Plastisol and polyurethane (Pural) are the cheapest. Prelaq or Hard Coat coatings are considered to be the most durable. Steel systems are characterised by high mechanical strength and resistance to weathering. They should last up to 100 years. But they are also 20-30% more expensive than plastic ones. Steel elements are connected by roofing adhesive, sealant or gasket connectors. Steel systems are offered by many manufacturers of metal roofing tiles, so gutters and downpipes can be purchased in the same colour as the roofing.
Similarly to steel, aluminium sheet with a thickness of 1-1.5 mm is coated with a polymer layer. Aluminium is resistant to corrosion, so even where the coating is slightly damaged it will develop a natural patina. The durability of aluminium systems is estimated at 100-120 years. Such guttering is approximately 75% more expensive than plastic. Installation is also expensive, as it requires professional teams. The systems are usually riveted and glued.
Zinc-titanium sheeting is an equally expensive solution to aluminium. The material is a very durable zinc alloy sheet with a small admixture of titanium and copper. Zinc-titanium covers itself with a patina, which is a protective layer, so such guttering will last up to 120 years. The solid metal sheet, 0,7-0,8 mm thick, is mechanically resistant. The guttering is installed using roofing sealants, gasket joints or soldering. This is a job for specialists.