A roof is the uppermost part of a building that provides protection from animals and weather conditions like rain, snow, sunlight, heat etc. While building residential houses, most roofing companies encourage owners to use sloped roofs. These roofs do not let water or rain build up on them. Standing water can collapse a flat roof posing dangerous risks to the occupants of the house. Flat roofs cannot endure the weight of snow buildup and heavy rains and eventually breakdown or leak along the seams.
Flat roofs cover a large area. This makes them less stable compared to the sloped roofs. The weight of the roof has to be compensated for on the interior. This means more building materials and an increase in the expenses. The initial cost for installing a flat roof is also relatively higher than the sloped roof.
Thirdly, there is lack of roofing materials. Despite the fact that materials like rolled roofing, rubber and Bitumen are available and inexpensive, they have a limited lifespan of ten to fifteen years. The materials that can be installed in combination with them e.g. polycarbonate roofing are expensive. They also lack history that would help one predict how long they will last.
The flat roof collect a lot of debris and dirt than the sloped roof. A homeowner whose roof is flat, will clean his roof a lot more often. This is tedious and time consuming. Sometimes, one may need help to clean the roof and that brings in unnecessary expenses.
It is very difficult to find out any leakage on the roof. This means that repairing the roof is also difficult. One cannot repair a roof and they cannot see any cracks, leakage or fault. Temperature fluctuations can cause these roofs to form cracks. The repeated expansions and contractions result to cracked joints, flashing become detached and the seams begin to tear loose.
Lastly, flat slabs require more construction time. This means that more workforce is needed, more money has to be spent and a lot of materials are used up in the process. The dead load for a flat slab is also relatively higher than that of a sloped roof. As a result, the size of the structural members for flat slabs are bigger than those of sloped roofs.
However, in countries where flat roofs are not illegal by the government or any local powers that be, most residents will still prefer them to the sloped roofs.