Modified Bitumen in San Gabriel Valley-Flat Roof Repair
A flat roof lasts longer if it is properly maintained. Some assessors use 10 years as an average life cycle, although this is dependent on the type of flat roof system in place. Some old tar and gravel roofers acknowledge that unless a roof has been neglected for too long and there are many problems in many areas, a BUR (a built up roof of tar, paper and gravel) will last 20–30 years. There are BUR systems in place dating to the early 1900s.
Modern cold applied liquid membranes have been durability rated for 30 years. If standard fiberglass polyester resin is used such as the same resin used in boat repairs, then there will be problems with the roof being too inflexible and not able to accommodate expansion and contraction of the building. A fit-for-purpose flexible/elastomeric resin system used as a waterproofing membrane will last for many years with just occasional inspection needed. The fact that such membranes do not require stone chippings to deflect heat means there is no risk of stones blocking drains. Liquid applied membranes are also naturally resistant to moss and lichen.
General flat roof maintenance includes getting rid of ponding water, typically within 48 hours. This is accomplished by adding roof drains or scuppers for a pond at an edge or automatic siphons for ponds in the center of roofs. An automatic siphon can be created with an inverted ring-shaped sprinkler, a garden hose, a wet/dry vacuum, a check valve installed in the vacuum, and a digital timer. The timer runs two or three times a day for a minute or two to start water in the hose. The timer then turns off the vacuum, but the weight of water in the hose continues the siphon and soon opens the check valve in the vacuum. The best time to address the issue of ponding water is during the design phase of a new roofing project when sufficient falls can be designed-in to take standing water away. The quicker the water is got off the roof, the less chance there is for a roof leak to occur.
All roofs should be inspected semi-annually and after major storms. Particular attention should be paid to the flashings around all of the rooftop penetrations. The sharp bends at such places can open up and need to be sealed with plastic cement, mesh and a small mason's trowel. Additionally, repairs to lap seams in the base flashings should be made. 90% of all roof leaks and failure occur at the flashings. Another important maintenance item, often neglected, is to simply keep the roof drains free of debris. A clogged roof drain will cause water to pond, leading to increased "dead load" weight on building that may not be engineered to accommodate that weight. Additionally, ponding water on a roof can freeze. Often, water finds its way into a flashing seam and freezes, weakening the seam.
For bitumen-based roof coverings maintenance also includes keeping the tar paper covered with gravel, an older method, currently being replaced with bituminous roofing membranes and the like, which must be 'glued' in place so wind and waves do not move it causing scouring and more bare spots. The glue can be any exterior grade glue like driveway coating.
Maintenance also includes fixing blisters or creases that may not yet be leaking but will leak over time. 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. Any moisture trapped in a blister has to be dried before being repaired.
Roof coatings can be used to fix leaks and extend the life of all types of flat roofs by preventing degradation by the sun (ultra-violet radiation). A thickness of 30 dry mils is usually preferred and once it is fully cured, you will have a seamless, watertight membrane.
Infrared thermography is being used to take pictures of roofs at night to find trouble spots. When the roof is cooling, wet spots not visible to the naked eye, continue to emit heat. The infrared cameras read the heat that is trapped in sections of wet insulation.
A flat roof repair is a roof which is almost level in contrast to the many Modified Bitumen in San Gabriel Valley. 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 or less. Construction methods
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. 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, UV rays and weather off it and helps protect it from cracking or blistering and degradation. Roof decking is usually of plywood, chipboard or OSB boards (OSB = Oriented Strand Board, also known as Sterling board) of around 18mm thickness, steel or concrete. The mopping of bitumen is applied in two or more coats (usually 3 or 4) 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.
In some microclimates or shaded areas these rather 'basic' felt roofs can last well in relation to the cost of materials purchase and cost of laying them, however the cost of modern membranes such as EPDM has come down over recent years to make them more and more affordable. There are now firms supplying modern alternatives.
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. There are health risks to people and animals breathing the mold 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 (be it traditional or a modern membrane), 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.
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, puddle 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, PVC (polyvinyl chloride), TPO (thermoplastic polyolefin) 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 meter widths are bonded together in either hot or cold seaming processes during the fitting process, where labor 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.
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.
Traditionally the smelly, hot, physically demanding and sometimes dangerous work of tarring flat roofs has often meant that uneducated fitters of doubtful reputation have done work to a poor standard: This together with a lack of regular inspection and maintenance has meant that flat roofs have a poor reputation and there is an unwillingness to retain or to build them, which is unfortunate, given the potential usefulness of flat areas, the more so with the excellent performance of modern membranes, many of which come with long warranties and provide an excellent roof covering.
Modified Bitumen in San Gabriel Valley - Flat Roof Repair