Flat roof
In warmer climates, where there is less rainfall and freezing is unlikely to occur, many flat roofs are simply built of masonry or concrete and this is good at keeping out the heat of the sun and cheap and easy to build where timber is not readily available.
Materials that cover flat roofs typically allow the water to run off from a slight inclination or camber into a gutter system.
The felt paper is in turn covered with a flood coat of bitumen (asphalt or tar) and then gravel to keep the sun's heat, ultraviolet light and weather off it and helps protect it from cracking or blistering and degradation.
If a leak does occur on a flat roof, damage often goes unnoticed for considerable time as water penetrates and soaks the decking and any insulation and/or structure beneath.
If the problem is detected early enough, the insulation may be saved by repairing the leak, but if it has progressed to creating a sunken area, it may be too late.
One problem with maintaining flat roofs is that if water does penetrate the barrier covering, it can travel a long way before causing visible damage or leaking into a building where it can be seen.
Modern flat roofs can use single large factory-made sheets such as EPDM synthetic rubber, polyvinyl chloride (PVC), thermoplastic polyolefin (TPO) etc.
are available from the membrane manufacturer and can be well bonded to the main sheet, whereas with materials such as tar papers this is usually not the case – a fitter has to construct these shapes on-site.
For one-off works, old carpet or smooth wooden planks for workers to walk or stand on will usually provide reasonable protection.
Le Corbusier's theoretical works, particularly Vers une Architecture, and the influential Villa Savoye and Unité d'Habitation prominently feature rooftop terraces.
Le Corbusier only narrowly avoided a lawsuit from the family because they had to flee the country as France succumbed to the German Army in the Second World War.
The chief benefit of PMR design is that the covering protects the waterproofing membrane from thermal shock, ultraviolet light and mechanical damage.
However, when flat roofs are constructed in temperate climates, the need to support snow load makes additional structural strength a common consideration in any event.
Sedum is emerging as a favorite as it is easily transported and requires little maintenance as it is a succulent plant which remains close to the ground throughout its growth, has mild roots which do not damage the waterproofing membrane and changes colour in the seasons in greens, browns and purples to give a pleasing effect to the eye.
Seaming and detailing has evolved over the years and is fast, simple and reliable with many membranes including factory applied tape, resulting in a faster installation.
Mechanically attached roof membranes are held in place with nails and are suitable in some applications where wind velocities are not usually high.
It is widely used in New Zealand and other parts of the world for flat and low-slope roofs due to its exceptional durability, flexibility, and waterproofing capabilities.
After environmental concerns in the late 1990s companies began to feel pressured regarding some of the common adhesives and bonding chemicals, and some jurisdictions passed regulations limiting the use of CSPE membranes.
[12] The final modified bitumen sheet goods are typically installed by heating the underside of the roll with a torch, presenting a significant fire hazard.
Another problem developed when a lack of standards allowed a manufacturer to produce the product with insufficient APP, requisite to enhancing the system aging characteristics.
No open flames or other heat sources (as are required with torch on felts) are needed and the glass fiber reinforced systems provide seamless waterproofing around roof protrusions and details.
In the next step, known as polymerization, the VCM molecule forms chains, converting the gas into a fine, white powder – vinyl resin – which becomes the basis for the final process, compounding.
[15] PVC roofing is a Thermoplastic system, meaning that it is heat-welded at the seams forming a permanent, watertight bond that is typically stronger than the membrane itself.
PVC resin is modified with plasticizers and UV stabilizers, and reinforced with fiberglass non-woven mats or polyester woven scrims, for use as a flexible roofing membrane.
While more difficult to form into unique shapes, they instead offer greater bonding strength and longevity compared to thermoset roofing, although they often require specialized training and tools.
The durability and lightweight properties of GRP make it the ideal construction material for applications as diverse as lorry aerofoils and roofs, boats, ponds and automotive body panels.
GRP is also used in hostile industrial settings for applications such as tanks and underground pipes; this is due to its ability to withstand high temperatures and its resistance to chemicals.
[citation needed] Modern cold applied liquid membranes have been durability rated by the British Board of Agrément (BBA) for 30 years.
They may need experienced help as they require scraping away the gravel on a cool morning when the tar is brittle, cutting open, and covering with plastic cement or mastic and mesh.
Roofing systems that can deliver high solar reflectance (the ability to reflect the visible, infrared and ultraviolet wavelengths of the sun, reducing heat transfer to the building) and high thermal emittance (the ability to release a large percentage of absorbed, or non-reflected solar energy) are called cool roofs.
