Commercial Flat Roofing
As experienced flat roofing contractors, we offer a complete range of flat roofing services to meet the needs of all commercial and large residential properties.
Flat roofing systems are extremely durable and cost effective, making it a smart choice for your building. Our services include liquid applied systems, bituminous roofing felt and mastic asphalt roofing, all of which are designed to apply a seamless continuous membrane across your roof, giving your roof total waterproofing.
General speaking flat roofs by design are much easier to access and maintain, and if done so correctly can in many cases last much longer than the guarantees offered.
Our flat roofing services are available in London and the South East.
Built Up Felt Roofing Systems
High performance, roofing felt membranes are usually laid in several layers, one on top of another, as part of a system, with staggered overlaps, ensuring greater security. They are usually manufactured with a ‘carrier’ which is then saturated with bitumen. The quality of both the carriers and the bitumen has improved beyond recognition, resulting in strong, flexible, long life systems. The build-up of these advanced membranes is usually thicker than any other option and is less likely to be punctured during occasional access for maintenance.
Roofing felts these days are mainly ‘torch on’ and are applied by using heat from a gas gun. However, greater awareness of the risks of naked flames has forced innovation and most manufacturers offer complete or partial cold applied systems, which are applied with adhesives and hot air guns. When assessing our Clients’ needs we take into account the fire risks and recommend the use of either a complete cold applied systems or a cold alternative in risk areas of the roof.
Roofing felts are as durable as anything else on the market (except some metals) and in most cases they provide the most cost effective solutions.
Liquid Applied Waterproofing Membranes (Roofs, Walkways And Balconies)
Similar to roofing felt membranes except that the system is ‘built’ on the roof. A cold applied liquid is applied, and a reinforcing membrane (usually glass fibre or polyester) is laid into it. Once it has become saturated another one of two layers of the liquid are applied creating a strong flexible membrane.
Liquid applied systems can be used in any environment but particularly lend themselves to complex roofs with lots of details and penetrations. In these situations, they create a seamless, bespoke waterproofing membrane. They are also useful on buildings with difficult access because the components are relatively lightweight and can be transported to the roof more easily in lifts, reducing the necessity for expensive scaffolding and hoists.
One of their greatest advantages of liquids is that they are applied without the use of heat so there is no fire risk. They provide an easy to apply, fast, reliable solution
Mastic Asphalt Roofing
Rock Asphalt was originally transported to the UK from Trinidad in tankers with boilers which kept it fluid. Because of this trade many of the first asphalt contractors were based around the docks in East London, where the material is still more popular than anywhere else. These days synthetic Mastic Asphalt is used. Whilst not as durable as the original asphalt, it is a hot liquid applied system which offers many of the benefits of Liquid Applied Roofing Systems. It can be used on complex roofs with many features and penetrations to form a seamless waterproofing membrane. The finished waterproofing membrane is thick (approx. 22mm when complete) and robust and is suitable for occasional access for maintenance and the like. The membrane is not reinforced and is at its best on concrete or other stable substrates with less movement. It becomes soft when warm so cannot stand direct point loads. Due to its weight it requires a much stronger foundation than other roofing materials.
Like most liquid systems, in the event of damage asphalt can be easily repaired. The material is carbon neutral and can be recycled, making it an environmentally friendly choice.
Insulation, Decking And Roof Lights
One of the reason that early flat roofs were so unreliable was that no consideration was taken to overcome condensation which formed in the flat roof void under the roof deck. This problem was compounded when insulation was introduced and central heating was installed. Condensation formed in the roof void, saturating the components and rotting the structure, roof deck and creating attacks of dry and wet rot.
The industry has learnt from the failures of the past and there are three systems commonly in use to insulate flat roofs. There is a warm roof, where the ‘deck’ of the roof is below the insulation. The ‘deck’ of the roof is the section of the roof onto which everything is placed, with the exception of a cold roof. A cold roof is where the insulation is below the roof ‘deck’. A gap will be left for ventilation, as condensation can occur otherwise. In both these cases the top layer will be a weather membrane, dependent on the most suitable for your roofing project.
Finally, an inverted roof, which is when the insulation goes above the weather membrane. This protects both the ‘deck’ and membrane from heat and cold. The top layer is often gravel or concrete casting.
Roof lights are available for both flat roofs and pitched roofs. Whether you’re looking for a small area to let in natural light, or completely opening up your roof covering, we’re on had to assist. We can not only carry out the work, but advise on ways to ensure the building stays environmentally efficient when considering such options.
Living and Sustainable Ecological Roofs
A green or living roof, is a roof surface that is covered with vegetation ranging from trees, shrubs and extensive planting, like the Kensington Roof Gardens in London, built in the 1930s, to a thin layer of vegetation such as sedum of wildflowers. A green roof may include a water retention layer, filtration layers, a growing medium and planting. Both pitched and flat roofs (and even vertical walls) can be used as green roofs. There are a variety of different options available which can be tailored to each Clients’ needs. Green roofs are often used to landscape areas over car parks.
For Clients who are concerned about the environment, looking to save money over the long term and create a unique recreational space, a green roof offers a whole host of benefits. Here are just a few of them. And remember, if you would like more advice on green roofs please contact us.
Green roofs absorb precipitation so that while it will still drain through the growing medium it will be at a much-reduced rate which reduces the risk of flooding, particularly in urban areas. The plants on a green roof contain moisture which provide and additional fire break. As well as proving and important oasis for urban wildlife, green roofs absorb pollutants in the air and tests have shown that the streets surrounding a building with a green roof have a significantly lower concentration of particulates in the air. In addition to providing additional insulation green roofs also have a cooling affect in summer so that air conditioning and heating costs are reduced throughout the year.
Green roofs protect the roof waterproofing system from ultraviolet light and from the worst extremes of the weather, greatly increasing its life and reducing the maintenance costs over the life of the building. And contrary to popular belief, green roofs formed with vegetation blankets, particularly sedum, are low maintenance.
Lead Sheet and Hard Metals
Metal is a durable option for roofs with a low pitch, known for their longevity and durability, when installed correctly require little to no maintenance and should last decades. There are numerous types, including corrugated panels and standing seam.
Cold VS. Warm Roofs
Cold roofs rely on insulation laid between the roof joists with an air path of at least 50mm between the top and the underside of the roof deck. This void has to be ventilated sufficiently well to ensure that any moist air which gets into it is blown away before it condenses. In refurbishment projects, ensuring adequate ventilation is very difficult to achieve, particularly given the increased depth of insulation now required under building regulations. Therefore, it is very infrequently used.
Warm roofs are formed by laying a rigid insulation board on top of the roof structure. It is laid over a vapour control layer and the waterproofing is laid in top of the insulation. The vapour control prevents any moisture in the hot air rising from within the building from reaching the condensation point. As well as providing all the usual benefits of good insulation, this system also keeps the roof warm and at a more constant temperature, thus reducing thermal expansion of the structure, which can put a great strain on roof membranes.
Flat Roofing Structures
Early flat roofs built after The Second World War, often used chipboard (a low cost modern invention). However, the industry soon learnt that chipboard and roofs are not a good combination, especially not when there was an condensation forming on it.
The same was true of Strammit board, a low cost material with good insulation materials, made of straw. Woodwool slabs were more successful but being brittle by nature, they could be very dangerous. All of these materials may be found when refurbishing old roofs and our recommendation would usually be to replace them. Particular care has to be taken because of the risk of failure while removing them.
These days roofing grade OSB3 boards are commonly used as well as roofing grade plywood. There are strict standards to which the boards must comply, not only in terms of their suitability for use in such a demanding location but also in terms of environmental concerns.
Most large buildings, shopping centers, hospitals, schools, office buildings and large residential developments are built with concrete or steel frames and roof decks.
Concrete roof decks are usually laid flat and level and the falls or gradients on the roof, necessary to allow water to drain off it, are created by the addition of either ‘screeds’, a secondary timber structure or insulation designed to create a slope. Metal roof decks are also normally built level and flat although occasionally they may be designed with a gradient. Otherwise, the same methods which are used on concrete decks are also commonly used.