residential flat roof

A protected membrane roof (PMR) is a roof where thermal insulation or another material is located above the waterproofing membrane. Modern green roofs are a type of protected membrane roof.

This development has been made possible by the creation of waterproofing membrane materials that are tolerant of supporting a load and the creation of thermal insulation that is not easily damaged by water. Frequently, rigid panels made of extruded polystyrene are used in PMR construction.

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The chief benefit of PMR design is that the covering protects the waterproofing membrane from thermal shock, ultraviolet light and mechanical damage. One potential disadvantage of protected membrane roof construction is the need for structural strength to support the weight of ballast that prevents wind from moving rigid foam panels or the weight of plants and growth media for a green roof.

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.

1. Leaks

Some residential flat roof contractors have been vulnerable to leaks because of their flat surface.

Water does tend to pool, particularly after heavy rain or snowfall; however, there is a fix for this problem.

A minor pitch is included in low-slope roofing systems for drainage and leak prevention.

Any sheet of material used to cover a flat or low-pitched roof is usually known as a membrane and the primary purpose of these membranes is to waterproof the roof area.

Materials that cover flat roofs typically allow the water to run off from a slight inclination or camber into a gutter system. Water from some flat roofs such as on garden sheds sometimes flows freely off the edge of a roof, though gutter systems are of advantage in keeping both walls and foundations dry.

Gutters on smaller roofs often lead water directly onto the ground, or better, into a specially made soakaway. Gutters on larger roofs usually lead water into the rainwater drainage system of any built up area.

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Occasionally, however, flat roofs are designed to collect water in a pool, usually for aesthetic purposes, or for rainwater buffering.

Traditionally most flat roofs in the western world make use of tar or asphalt more usually felt paper applied over roof decking to keep a building watertight.

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.

Roof decking is usually of plywood, chipboard or oriented strand board (OSB, also known as Sterling board) of around 18 mm thickness, steel or concrete. The mopping of bitumen is applied in two or more coats (usually three or four) as a hot liquid, heated in a kettle.

A flooded coat of bitumen is applied over the felts and gravel is embedded in the hot bitumen.

A main reason for failure of these traditional roofs is ignorance or lack of maintenance where people or events cause the gravel to be moved or removed from the roof membrane, commonly called a built-up roof, thus exposing it to weather and sun. Cracking and blistering occurs and eventually water gets in.

Roofing felts are usually a 'paper' or fiber material impregnated in bitumen. As gravel cannot protect tarpaper surfaces where they rise vertically from the roof such as on parapet walls or upstands, the felts are usually coated with bitumen and protected by sheet metal flashings called gravel stops. The gravel stop terminates the roofing, preventing water from running underneath the roofing and preventing the gravel surfacing from washing off in heavy rains.

In some microclimates or shaded areas felt roofs can last well in relation to the cost of materials purchase and cost of laying them. The cost of membranes such as EPDM rubber has come down over recent years[when?].

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. This can lead to expensive damage from the rot which often develops and if left can weaken the roof structure.

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There are health risks to people and animals breathing the mould spores: the severity of this health risk remains a debated point. While the insulation is wet, the “R” value is essentially destroyed.

If dealing with an organic insulation, the most common solution is removing and replacing the damaged area. 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.

Thus, it is not easy to find the source of the leak in order to repair it. Once underlying roof decking is soaked, it often sags, creating more room for water to accumulate and further worsening the problem.

2. Poor Insulation

Insulation and ventilation space is scarcer on low-pitch roofs than on steep-pitch ones. This means that flat roofs may not be as efficient in deflecting heat from entering the structure as they should be.

Some residential flat roof contractors recommend using roof coatings and other energy-efficient materials to withstand heat absorption as a solution to this challenge.

A flat roof is a roof which is almost level in contrast to the many types of sloped roofs. The slope of a roof is properly known as its pitch and flat roofs have up to approximately 10°. 

Flat roofs are an ancient form mostly used in arid climates and allow the roof space to be used as a living space or a living roof.

Flat roofs, or "low-slope" roofs, are also commonly found on commercial buildings throughout the world.

The National Roofing Contractors Association defines a low-slope roof as having a slope of 3 in 12 (1:4) or less.

Flat roofs exist all over the world, and each area has its own tradition or preference for materials used.

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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.

In areas where the roof could become saturated by rain and leak, or where water soaked into the brickwork could freeze to ice and thus lead to 'blowing' (breaking up of the mortar/brickwork/concrete by the expansion of ice as it forms) these roofs are not suitable.

Flat roofs are characteristic of the Egyptian, Persian, and Arabian styles of architecture.

Around the world, many modern commercial buildings have flat roofs. The roofs are usually clad with a deeper profile roof sheet (usually 40mm deep or greater).

This gives the roof sheet very high water carrying capacity and allows the roof sheets to be more than 60 metres long in some cases.

The pitch of this type of roof is usually between 1 and 3 degrees depending upon sheet length.

3. Reduced Eye-Catching Aspects

You'll obtain a traditional look that most homeowners want with a pitched roof. With a residential flat roof, there are fewer custom angles and slopes.

Even though the design may be constrained, it is still an excellent option. The added living area more than makes up for its lack of aesthetic appeal on the outside.

This is also great for home use since it has a more updated style.

Another common reason for failure of flat roofs is lack of drain maintenance where gravel, leaves and debris block water outlets (be they spigots, drains, downpipes or gutters).

This causes a pressure head of water (the deeper the water, the greater the pressure) which can force more water into the smallest hole or crack.

In colder climates, puddling water can freeze, breaking up the roof surface as the ice expands. It is therefore important to maintain your flat roof to avoid excessive repair.

An important consideration in tarred flat roof quality is knowing that the common term 'tar' applies to rather different products: tar or pitch (which is derived from wood resins), coal tar, asphalt and bitumen.

Some of these products appear to have been interchanged in their use and are sometimes used inappropriately, as each has different characteristics, for example whether or not the product can soak into wood, its anti-fungal properties and its reaction to exposure to sun, weather, and varying temperatures.

Modern flat roofs can use single large factory-made sheets such as EPDM synthetic rubber, polyvinyl chloride (PVC), thermoplastic polyolefin (TPO) etc. Although usually of excellent quality, one-piece membranes are called single plies are used today on many large commercial buildings.

Modified bitumen membranes which are widely available in one-metre widths are bonded together in either hot or cold seaming processes during the fitting process, where labour skill and training play a large part in determining the quality of roof protection attained.

Reasons for not using one-piece membranes include practicality and cost: on all but the smallest of roofs it can be difficult to lift a huge and heavy membrane (a crane or lift is required) and if there is any wind at all it can be difficult to control and bond the membrane smoothly and properly to the roof.

Detailing of these systems also plays a part in success or failure: In some systems ready-made details (such as internal and external corners, through-roof pipe flashings, cable or skylight flashings 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. Success depends largely on their levels of skill, enthusiasm and training – results can vary hugely.

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Metals are also used for flat roofs: lead (welded or folded-seamed), tin (folded, soldered or folded-seamed) or copper. These are often expensive options and vulnerable to being stolen and sold as scrap metal.

Flat roofs tend to be sensitive to human traffic. Anything which produces a crack or puncture in the waterproofing membrane can quite readily lead to leaks. Flat roofs can fail, for example; when subsequent work is carried out on the roof, when new through-roof service pipes/cables are installed or when plant such as air conditioning units are installed.

A good roofer should be called to make sure the roof is left properly watertight before it is left. In trafficked areas, proper advisory/warning signs should be put up and walkways of rubber matting, wooden or plastic duck-boarding etc. should be installed to protect the roof membrane.

On some membranes, even stone or concrete paving can be fitted. For one-off works, old carpet or smooth wooden planks for workers to walk or stand on will usually provide reasonable protection.

Modernist architecture often viewed the flat roof as a living area. Le Corbusier's theoretical works, particularly Vers une Architecture, and the influential Villa Savoye and Unité d'Habitation prominently feature rooftop terraces.

That said, Villa Savoye's roof began leaking almost immediately after the Savoye family moved in. 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.

Conclusion

Swadley Roof Systems offers the best roofing services in the Houston, Austin, San Antonio and Dallas area.