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Flat Roofing

May 21, 2013PaddyArticles, Building materials, Flat roofing

Flat roofing

This article covers: All types of flat roofing

• Felt roofing
• Mastic asphalt
• Glass fibre
• Lead
• Other metals

Torch on Felt for flat roofing

Torch on Felt membrane roofing is now the most popular system used for flat roofing

As the title suggests, the technique involves heating a layer of bitumen that has been applied to the felt using a Propane gas torch, which melts the bitumen allowing it to bond to the substrate or under layers of felt previously applied. Together the layers form a flat roofing system. Traditionally the roll and pour method for felt flat roofing was used. This involved heating Bitumen in a specially designed boiler and transporting it to the roof in buckets.

Torch on felt membranes

The roll and pour method and still the Rolls Royce of installation & requires great skill -Note thumbs facing forward to avoid rolling hands into the hot bitumen @ 410 deg F

It would then be poured out and the felt rolled over the molten bitumen. This type of application is very specialised and dangerous and a major influence for the introduction of Torch on Felt. This application is far easier to use and subsequently has allowed installation to be carried out by inexperienced people. The correct installation of flat roofing is a skilled art and should only be carried out by suitably skilled contractors, so many of the problems associated with flat roofing are due to incorrect installation. Installed correctly with modern high tensile felt membranes, there is no reason why a flat roofing felt system should not last just as long as a tiled roof.

Whilst the advantages of having a Torch on Felt flat roofing system installed are obvious, there is a lot of choice on the market that can cause confusion. Some of these options available include torch-on, self adhesive, pour and roll and glass fibre membranes. Any roofing company will be able to give you professional roofing advice on the right type of flat roofing membrane for your property.

Torch-on membranes can be applied to a wide range of flat roofing scenarios in a relatively straightforward manner.

Felt flat roofing is generally applied in four layers comprising of:

• A vapour barrier - Normally glass fibre based
• Insulation layer - Closed cell ridged board in varying thicknesses.(Not applicable in all cases)
• Intermediate layer
• Cap sheet

Torch-on membranes are extremely effective and can provide you with a good quality roof for years to come. However, applying these can be dangerous and it is essential to consult a professional construction company if you are thinking about having one of these installed. Enlisting the help of professionals will ensure that the job is carried out correctly, whilst it will also prevent you from potential injury

Vapour barriers are applicable to all flat roofing systems.

A properly installed flat roofing system  should include a vapour control layer. A vapour control restricts water vapour from the dwelling damaging the insulation in a warm deck scenario  ie: where the insulating material is fitted to the roof decking.  Over time condensation can also cause any timber or support joists to rot. Replacing this is an extremely costly procedure, so to avoid this problem a vapour barrier control layer and insulation should always be fitted in your flat roofing system.

If you are fitting insulation between the roof joist then its imperative that the space is kept well ventilated. A build up of condensation over long periods can cause the timer structure to rot.

The vapour control layer is the first layer of the flat roofing to be installed. It is installed directly to the roof decking and should be fixed to the decking with clout head nails and sealed on the laps and perimeter. Few are aware of the importance of this layer, but when you consider the amount of moisture that can build up in a standard house you'll understand why these are necessary. A typical family home with two adults and two children living under normal conditions can create up to ten Litres of moisture over a 24 hour period. The moisture or water vapour has to go somewhere, and unfortunately not enough properties are adequately ventilated or insulated correctly to deal with this.

The list below highlights some factors that may indicate that your property is at risk from poor ventilation.

• Noticeable vapour in the inside of your property
• Moisture in building materials
• Moisture build-up on the floor, windows, or the walls of your property
• Black mould usually on external walls

Excessive vapour and condensation build up is more common in some properties than others. Older buildings usually have walls without insulation or cavities, and traditionally they had adequate ventilation from chimneys, draughty windows and doors. With modern living, home owners seal up the chimneys, fit sealed double glazed windows and doors, and the roof, more often than not, will have been renewed with a non permeable felt underlay.

These new developments cut out all the previous forms of ventilation and heat the property during the winter months. The warmer air will carry higher levels of moisture. Air will shed this excess moisture when it meets a cold surface. This is called the dew point. Properties with swimming pools will be exposed to particularly high levels of water vapour. Some rooms of every property are also more susceptible to vapour damage than others. Kitchens and bathrooms, for example, are more likely to suffer from problems with condensation.

Controlling moisture in a property is very important. Specialist building contractors will be able to assist and make recommendations. If your property meets any of the criteria that has been highlighted in this article, it is best to get professional help immediately, as delaying it could make matters worse.

Self-Adhesive felt for flat roofing.

A self adhesive membrane is perhaps the easiest roofing material to apply for flat roofing. The underside of this membrane uses soft bitumen to form a bond to the substrate or under layer. This makes the use of blow torches and bitumen redundant, and is typically used by the DIY enthusiast. It is fine for the use on outbuildings, sheds etc, however for more important applications it is better to use an alternative flat roofing option installed by a specialist.

Self adhesive flat roofing

When it comes to Bituminous flat roofing  there are generally two main choices. These choices are either, Asphalt or a Felt membrane roof. Although in previous years asphalt and was seen as extremely popular choice for all types of flat roofing , it is expensive and a high skill level is required to apply it correctly. Roofing technology has moved on and now felt membrane roofs are seen as the better choice for flat roofing as they offer a number of advantages. These advantages are listed below:

• They require little maintenance and have a long life span iof installed correctly.
• Cheaper andeasierto apply than other flat roofing materials

Even though felt flat roofing is easier to apply when compared to other types, roofing is not a job that should be carried out by a DIY enthusiast. It is a job that involves many risks and ideally you should speak to a professional roofer who will be able to carry out this task in a safe and efficient manner. Once you have spoken to a professional construction company, it is likely that you will be presented with a number of membrane options. These options can include torch-on, pour and roll, glass fibre and self adhesive membranes. The choice here can be overwhelming for some.

But before you make your mind up, ask a professional contractor who will be able to provide you with invaluable roofing advice whilst carrying out this skilled and potentially dangerous task.

Felt flat roofing. The roll and pour method.

For use by the specialist installer.

The roll and pour method

Pour and roll membranes are applied onto roofs by using hot bitumen. Bitumen is bi product of the petrol refining industry. Bitumen is supplied in 25kg blocks or tubs it is then usually broken up on site and heated in a specialist boiler until it is molten. Once at the correct temperature it is ladled into buckets- some boilers have taps to ease this process.

The felt for flat roofing is set out and cut to length. It is then rolled back- One operative will pour the molten bitumen on to the surface and the other will roll the felt over allowing the bitumen to squeeze out of each side. The surplus is then wiped over with wallpaper stripper.

The finish layer will usually have a mineral or slate chipped finish impregnated into the surface of the felt. Keeping this free of surplus bitumen. Using a roll and pour method is very skilled- that's why most companies that install flat roofing will now only use a torch on felt systems.

Most modern operatives wouldn't now know how to roll and pour a final mineral surface top layer. A rolled and poured roof is the king of felt roofing. The bond created is arguably stronger than the bond that is created when using a self adhesive or torch on membrane, but there are some drawbacks. Applying a membrane in this way is a skilled technique that will require the use of a professional roofer. There are fewer companies now who have the skills and equipment to carry out this type of installation, and it is more expensive, but applied correctly it is the Rolls Royce of felt roofing. There are a number of roofing companies that will be able to provide high quality services at competitive rates, whilst also ensuring that your roofing membrane is fitted correctly.

The demise and bad name associated with felt flat roofing

In some ways its quite sad but the roll and pour method was also responsible for the demise and poor name flat roofing has suffered. With the rising cost of bitumen many installers started to apply the bitumen using cotton floor mops so spreading it more thinly and saving money. This process caused a hit and miss bonding between the layers and a weakness in the overall system allowing water to permeate between the layers and causing leaks.

Pour and roll membranes for flat roofing will typically use three layers of felt membrane, and a final layer which is referred to as the cap sheet and will normally have a granular finish available in different colours. It can be argued that this is the best option if you are thinking about investing in a new flat roof. This of course will save you money in the long run. Companies who can undertake this type of installation properly are few and far between.

Mastic Asphalt for flat roofing

Mastic asphalt is a waterproof material that is used for flat roofing, also used on floors, paving and basements, but most commonly on flat roofing. Not often now seen due expense and modern easier to apply alternatives.

Asphalt is made up of a compound called bitumen. Bitumen is a by-product of the petroleum refinement stage, and within this compound the particles are bound together especially tight. In In order to add additional strength to mastic asphalt, fine aggregate is blended in. Aggregate types can vary dependant on use but often limestone is used for roofing grades and granite is added for paving use. This material is known as mastic asphalt.

Mastic Asphalt Roofing

Mastic asphalt is a building material that has a number of uses. It is used on pavements and flooring, but most importantly it is used in flat roofing. It is commonly used on the flat roofing of commercial buildings as it can create an extremely strong and durable roof that will accept traffic without causing damage. However point loading in very warm conditions is not recommended.

Mastic asphalt for flat roofing is generally applied in two coats. The material is supplied in solid blocks and is heated using a specialist boiler or mixer. It is poured onto the surface and, using a hard wood float, it is spread to the correct thickness. The second coat has dry sand applied to the top that is rubbed in. When it cures, a dense and solid material is created which is waterproof and impermeable.

The benefits of a mastic asphalt roof are obvious, but they still need to be installed correctly for them to reach their full potential. This article will look at some of the regulations and guidelines that are associated with mastic asphalt flat roofing, which need to be followed to ensure a professional finish.

When Applying Mastic Asphalt for flat Roofing Generally

Mastic asphalt needs to be applied in accordance with the traffic conditions and requirements of the roof.

• Where falls are more than 1:80, two 20mm coats of mastic asphalt are required
• Where falls are below 1:80, three thinner layers of mastic asphalt will be required generating no more than 30mm. These guidelines are in accordance with the BS 8218: 1998 regulations. When Applying Mastic Asphalt to Horizontal, Vertical or Sloping Surfaces
• On horizontal surfaces and pitches up to 10°, two 20mm coats of mastic asphalt will need to be applied on a separating membrane
• On sloping and vertical surfaces over 10°, three 20mm coats will need to be applied without a separating membrane
• On sloping and vertical surfaces over 10° which use timber or lightweight concrete, but not skirting, three coats of mastic asphalt that create a combined thickness of 20mm are required with no separating membrane
• On sloping and vertical surfaces over 10° which use timber or lightweight concrete, which includes skirting, three coats of mastic asphalt that create a combined thickness of 20mm needs to be laid onto metal lathing over a separating membrane
• On horizontal surfaces that are used as reservoirs, roof gardens or buried waterproofing, three coats of mastic asphalt that create a combined thickness of 30mm needs to be applied onto a glass fibre tissue membrane

Vapour Barriers for flat roofing

• Vapour barriers need to be laid onto a glass fibre tissue. A minimum 10mm vapour barrier thickness is required

Up-stands and skirting for flat roofing

• On up-stands or skirting that is not timber or lightweight concrete and is below 300mm in height, two coats of mastic asphalt are required to create a combined thickness of no less than 13mm
• On up-stands or skirting that is not timber or lightweight concrete and is above 300mm in height, three coats of mastic asphalt are required to create a combined thickness of no less than 20mm
• Two coats may be acceptable in areas that are not exposed to the outside, for example, tanking rooms or mechanical service areas
• On up-stands or skirting that is timber and lightweight concrete, three coats of mastic asphalt are required to create a combined thickness of 20mm. This needs to be applied on expanded metal lathing using a separating membrane
• On up-stands and skirting which has expanded metal lathing that is attached to concrete, brickwork or block work, three coats of mastic asphalt to a combined thickness of 20mm will need to be applied. This includes a separating membrane.

These are the requirements that are outlined in the BS 8218:1998 guidelines which should be followed if you want to obtain a safe, durable and legal roof. A decent roofing company will be able to abide by these regulations, and if you want a roof that is fitted professionally it is advisable to use a company that has relevant experience.

Glass Fibre Roofing ( GRP ) for flat roofing

Whether you need a new roof to replace a damaged one, or you are thinking about creating a new build, installing a roof will mean making a desision about what type is best. No roofs come cheap and the choice you make needs to be viewed as an investment. This important decision will affect the future salability of your property, so it is paramount that the right option is chosen.

Fibreglass flat roofing is an ideal choice for properties that have extensions or garages. Traditionally felt or asphalt is the material of choice for flat roofs, but since technology has advanced this no longer seen as the only option. Glass fibre is very durable and requires little maintenance and is a perfect choice for flat roofing.

Glass fibre roofing being installed

  Benefits for using GRP for flat roofing that are highlighted below:

• Extremely durable and hardwearing
• Can be exposed to all weather types
• A life-span that outlives many other flat roofing materials - a typical fibreglass roof will last at least 25 years
• Requires little maintenance and can be easily repaired if necessary
• A cheaper option to some flat roofing alternatives like lead, which means fibreglass is not a material that will be targeted by thieves
• Can be overlaid with tiles to form a patio or roof garden

Fibreglass roofs are also known as GRP (glass reinforced plastic). When installed layers of fibreglass matting are bonded in a two part resin it is then finished with a gel coat or top-coat that can be coloured to your specific choice. This top-coat is applied to the fibreglass roofing layer which promotes additional water resistance and durability. Top-coats and fibreglass roofing systems should be installed by a professional roofer for optimal results, but if you feel brave then you can use the information in this article to try and install a GRP roof yourself. However, it must be mentioned that installing a GRP without any knowlege of roofing or glass fiber is beyond the scope of most people. Enlisting the help of a professional is probably a better option. For information purposes however, a rough overview as to how a fibre glass flat roofing system is installed is outlined below.

This is what a completed glass fiber roof can look like

Assuming that the structure of the roof has plywood boards laid securely over the joists, a GRP roof can be installed. GRP cannot be fitted in conditions below 5°C and ideally this sort of task should only be undertaken during dry warm weather. Fibre glass matting is applied to the 18mm plywood boards, and then a specialist resin is applied using a roller or brush. Whwn this has cured a second layer of matting is applied .This adds to its durability and water resistance and is vital if you want to be able to get the best out of your new fibreglass roof. Upstands can be formed using strips of matting and drips or cappings can be bought purpose made and incorperated into the GRP flat roofing system. Finally a coloured top gell coat is applied to complete the flat roofing system.

As the bullet points below suggest, gaining a GRP roof is a popular option if you're looking at having a flat roofing system  installed on your property. Under most circumstances two experienced roofers can strip, re-deck, laminate and apply a top-coat to a roof at a rate of around 10 square meters a day.

Application of Fibre glass for flat Roofing

A fibreglass flat roof is a great alternative  to traditional materials for flat roofing such as felt or asphalt. Asphalt and felt are no longer seen as the flat roofing material of choice. Fibreglass is more durable and water resistant, whilst its life span is longer and it usually works out to be more cost effective. This article however is not looking at the advantages of fibreglass roofing, but it aims to provide some useful information that will come in handy when installing a GRP roof.

When laying any roof it is always advisable to check the weather conditions beforehand, but if you are going to fit a fibreglass flat roofing system in the winter the following tips will come in useful.

• Top-coating is essential to get the best out of a GRP roof, but avoid doing this after 2pm in the winter. The heat from the sun is essential if the resin is to cure, even when you have invested in a high quality top-coat that can cure at temperatures below 10°C
• When top-coating it is a good idea to warm the resin. This can be achieved by leaving it in a warm room over night which will make it much easier to apply the next day
• If it does start to rain, cover the roof with a waterproof sheet to protect it. Make sure you have one on standby in the event of this happening
• If you are running out of time and have not yet applied the fibreglass lamination layer, then coat the exposed plywood with a catalysed resin. This will protect wood from the elements allowing you to continue work at a later date
• It is vital for the wooden substrate to be completely dry before it is laminated with fibreglass. Trapped moisture will cause major problems

As already mentioned, the tips listed above are useful for people who plan to lay a fibreglass flat roof in the winter. However, different techniques will have to be employed if you plan on laying GRP flat roofing system in warmer months. These are outlined below.

• Hot weather can cause top-coating resin to dry quickly. Ideally small batches should be mixed up regularly, as opposed to mixing it all at once
• A top-coating should not be applied when the temperature is above 35°
• If a roof is top-coated in strong sunlight it will not be able to cure properly. It may be better to undertake this task later on in the day, which will save you from having to do it twice
• Apply the fibreglass laminate in short runs. By doing this the resin is less likely to catalyse and consequently have a negative impact on your roof

These tips regard the installation of your fibreglass flat roofing system, but what about caring for the tools that you have used?

Acetone is an essential product for cleaning your tools. This can be applied to paintbrushes and polyester rollers, but not the bucket that you have mixed your resin in. To keep this clean, coat the bottom of your bucket with resin. After it has cured it can be peeled out, which makes it instantly clean for the next task. Under no circumstances is it advisable to wash your hands with acetone, as it's a strong chemical that is dangerous to your skin.

Here is another example of a stylish fibre glass roof.

These tips are useful if you are planning to fit a fibreglass flat roofing system yourself, but for high quality results it is advisable to use a professional roofing company. Professional roofers will have years of experience when it comes to undertaking tasks like this, and it is in their best interest as professionals to install a roof that is functional, durable and attractive.

Lead for flat Roofing

Roofing materials come in a variety of forms, but arguably the best traditional materials for flat roofing is lead. Most traditional roofs use lead as it is an extremely durable material that can last for generations. It provides easy malleability when compared to other metals and is ideal for guttering, flashings and bridging junctions. Although lead roofing can be expensive, it provides a beautiful, timeless finish that is ideal for properties that want to maintain a traditional look and should not be overlooked as a flat roofing system.

Specialis Roofing companies will undertake this kind of work primarily using lead in that are manafactured in 6m Rolls. The lead is laid and dressed onto timber boards which create a weatherproof surface all year round, whilst their life span can last in excess of a hundred years. This technique has been applied to buildings throughout the country for centuries and it remains a tried and tested roofing method.

Lead Roofing

Lead sheets for flat roofing come in a variety of weights and sizes. Code numbers are used to determine these differences in weight, and generally each sheet will be given a number between 1 and 7. This number refers to the weight in pounds per square foot. So for example, code 6 basically means that the lead sheets weigh six pounds per square foot, and this rule applies to each number.

While lead roof work is generally undertaken on larger historic buildings, it can also provide the same benefits for smaller  modern properties. This has led to an increased popularity for flat roofing in recent years, but there are some drawbacks that people need to be made aware of. Even though lead roofs are extremely durable, they do have a tendency to "creep" down. This is due to the heavy weight of lead, and the heating and cooling effect that the seasons can have on it. But despite this problem, lead roofing is still seen as the most durable and cosmetically pleasing roofing material on the market.

Like all roofing work, lead for flat roofing will have to be installed or maintained by a professional. It is a skilled job with a number of inherent risks and so it is not something that should be undertaken by a DIY enthusiast. If you feel that your property could benefit from the many advantages of lead roofing, speak to a professional building contractor.

Lead Sheet

Lead is a building material that has been used in roofing for centuries. It provides excellent levels of durability and water resistance, whilst guaranteeing a low maintenance roof that is sure to last for generations. To have a lead roof installed properly, high quality lead sheet will have to be used. This article will go on to look at a few specific details that need to be considered before purchasing or fitting lead sheet.

The majority of lead sheet will be described as "milled lead sheet". This term is used to describe the manufacturing process that it undergoes in order to meet British standard building requirements. These building standards are highlighted in the BS 1178 document, which states that all milled lead sheet will have to have a minimum chemical composition of 99.9%, while it will also have to meet industry standard sizes. These sizes are given code numbers which represent the dimensions of the lead sheet. The codes and their corresponding sizes are displayed in a table below.

CODE NUMBER.	THICKNESS (mm).	WEIGHT(kg/m2)	THICKNESS(Decimal.)	THICKNESS(Nearest inches.)	WEIGHT(Lbs/sq ft.)
3	1.25	14.18	0.049	3/64" +	2.91
4	1.80	20.41	0.071	5/64" -	4.19
5	2.24	25.40	0.088	3/32" -	5.21
6	2.50	28.36	0.098	3/32" +	5.82
7	3.15	35.72	0.124	1/8" -	7.33
8	3.55	40.26	0.140	9/64" -	8.26

These codes represent the diameters displayed above, but to make life easier they are also colour coded. These are as follows.

• 3 = Green
• 4 = Blue
• 5 = Red
• 6 = Black
• 7 = White
• 8 = Orange

The majority of lead sheeting in the UK will follow these dimensions and their corresponding colour codes, but there will be times when larger pieces of lead sheet will be required. Typically these extra large sheets are created to meet dimensions that measure up to 12m in length, by 2.40m in width. All lead sheets can alternatively be made to measure by the manufacturer, but there will be times when thinner lead sheet is required. These thinner sheets are not usually used in roofing, but they are sometimes used for X-ray protection and sound insulation. As a result these thinner lead sheets are not colour coded and built to industry standard regulations, but they are often used as part of lead-cored bitumen felt which is typically used to provide a high quality damp proof course.

The standard measurements that lead sheeting comes in (code No. 3-8) will usually meet all of your building and roofing needs. This will include flashings, weathering's, cladding and the majority of all external lead work, but this is assuming that there are no additional factors that need to be accounted for. For example additional thickness may be required to provide protection against thermal movement and mechanical damage, while having a sufficient amount of metal when dressing, bossing or shaping lead will also need to be taken into consideration.

Cast Lead Sheeting for flat roofing.

So far this article has looked at the typical dimensions and measurements that are associated with lead sheeting, but little has been said about the various types available. Firstly there is "cast-lead" sheeting. Cast lead sheeting is made using a tried and tested method that involves pouring molten lead over a bed of prepared sand. In most cases this type of lead sheeting is used to replace older roofs, but as these are in decline, so is this type of roofing material. Nevertheless this material continues to be in use in the UK, but as it's largely created in independent manufacturing plants there are no set industry standards. This means that variations will occur, but generally sheets come in sizes that correspond to code numbers 6, 7 and 8 on the milled lead sizing chart highlighted above. The texture and consistency of this material will differ slightly when compared to more refined lead sheeting, but ultimately there are no real differences with regards to its durability and its practicality.

Machine Cast Lead Sheeting for flat roofing

Machine cast lead sheeting is another option that is available. As the name suggests, this type of lead sheeting is made by a machine which allows for increased precision and regulated dimensions. Typically these sheets will come in sizes that vary between 0.4mm - 1.2mm in thickness, while their maximum width will usually reach 1.2m.

Lead Laminates for flat roofing and wall cladding

For extra support, sound insulation and resistance to radiation, lead laminates are used instead of more conventional lead sheeting types. Lead laminates use thinly milled lead sheeting which is laminated onto a board substrate such as plywood. The combination of these materials essentially creates a panel that is useful for both flat roofing and external wall cladding. These provide exceptional protection against thermal movement, but the bond between the outer material and the inner layer of lead has to be strong in order for them to function properly. The strength of this bond is especially important if the laminate panels are going to be used for external purposes, but for internal usage, this is less of an issue. Regardless, it is always best to purchase them from a reputable company that specialises in making them.

As we can see the main choices for lead flat roofing are milled, cast lead, machine cast lead and lead laminates. All of these have a number of advantages and disadvantages which will suit some properties better than others, but ultimately all of them will require similar accessories and fittings. Ideally an experienced installer will fit the type of lead system that has been chosen, but regardless of who fits it the following materials will be required.

• Copper clips - all copper clips used should meet BS 2870 standards. They need to be cut from a copper sheet no less than 0.6mm in thickness, while at a temper grade of ¼ H
• Nails - all nails used need to be copper clout nails that conform to BS 1202 (part 2 table 2) industry standards. They need to be a minimum of 25mm long, with a minimum shank diameter of 10SWG
• Screws - these need to be a minimum of 25mm long with a diameter that doesn't exceed 10 SWG. These need to conform to BS 1210 regulations
• Solder - all solder used for fixing dots, angles or seams will have to conform to BS 219 regulations. Grade D or grade J should be used
• Underlay - this will depend on the surface that the underlay is fitted onto. Waterproof building paper that conforms to BS 1521 regulations will be suitable for most construction work, assuming that the substrate surface is relatively even and smooth

So while the lead sheeting used will have to meet BS 1178 regulations, the accessories used to fit it will also have to meet the guidelines highlighted in the bullet points above. If the materials used do not abide by these guidelines, then any work that has been carried out could be deemed illegal and unsafe. To ensure that these standards are met, always use a registered construction company complete with the necessary insurance and qualifications.

Now that the different types, standards, dimensions and accessories of lead sheeting for flat roofing have been looked at in some detail, the actual properties of lead as a material need to be considered. To start with, it is the softest of all common metals making it extremely malleable and easy to shape. This can be done with hand tools and without risk of fracture, making it ideal for intricate aspects of metal work. With regards to flat roofing, it is often used for flashings and areas that need to be fitted tightly to the surface of a structure. A good example of this is a contoured region or a particularly challenging aspect of single-lap tiling. These examples demonstrate the versatility that is associated with using lead as a roofing material, but to fully appreciate the benefits of lead, more technical qualities need to be analysed.

note the precision work in the lead roofing details

As lead sheets are predominately used as a roofing material it is likely they will be exposed to the elements on a regular basis. This can have a big impact on lead, and it is not unusual for it to be subjected to linear expansion. Linear expansion is the process that can cause any metal to expand and contract when exposed to heat, and in lead's case this can easily occur at around 40 °C. Unfortunately this is a temperature that can be reached on a hot day, and when this occurs lead can begin to crack. This is obviously a negative effect that can distort a roof, but there are steps to be taken that prevent this.

The linear expansion for lead is 0.0000297 at 1°C, which means that a 2 meter sheet of lead could expand by about 2-3mm when exposed to heat. To stop this from happening and subsequently reduce the levels of thermal movement, it is vital to fit lead sheeting in smaller pieces. Even though there is no set industry standard that relates to the size of each sheet used and their susceptibility to thermal movement, there will be manufacturer's recommendations. It is vital to follow these for a properly installed lead roof, and as a general rule of thumb, the thinner the sheet the smaller the piece

Copper for flat roofing and wall cladding.

If you want a flat roofing system that really stands out from the crowd whilst also offering superb durability and weather resistance, then look no further than copper roofing. The colour of copper makes this metal seem unique when compared to other roofing materials, and undoubtedly this is the reason why it is often chosen. The effect that copper roofing creates can be breathtaking, especially as it can change over time, but they offer so much more than simply being cosmetically pleasing.

Copper sheet roofing

Copper flat roofing systems are typically fitted using the standard seam technique. This technique pays careful attention to the design of the roof, especially where chimneys and gullies are concerned. Once the layout of the roof has been taken into consideration, copper sheets will be secured over a layer of asphalt which is attached to the frame of the roof. The copper sheets will be secured by stainless steel clips, which are then welded between the up stands of the copper bays. This is a task that needs to be carried out by a professional flat roofing company that specialises in this type of flat roofing material .

While there are advantages of a copper roof over more conventional materials, the main reason why they are usually considered typically boils down to aesthetics. Copper roofs add elegance and class to any property, and if money wasn't an issue they would be the first choice for a lot of people.

Zinc for flat roofing and wall cladding.

Metal roofing materials are becoming increasing popular for flat roofing. Traditionally lead and copper  can be extremely expensive. Zinc roofs provide an alternative that allow for similar levels of durability, whilst retaining the benefits that they create for generations but at less cost

Zinc sheet roofing, For a classic contemporary look.

As a flat roofing material, zinc is extremely versatile. it can be adapted to cater for complex roof designs and wall cladding.  If you are thinking about building or updating a roof that contains either of these features, then perhaps zinc is a good choice for you. Fortunately there are specialist roofing companies who are familiar with zinc flat roofing systems.

Overall, zinc roofs are durable, require little maintenance and have great longevity. They share a number of characteristics with copper, in that they both create patinas and are metal based, but ultimately zinc provides a cheaper and more versatile option. Some people will argue that copper roofs are more pleasing to the eye, but this of course is a matter of personal opinion. To gain a zinc roof with a high quality finish, make sure that you enlist the help of a professional roofer. Roofing is not a task for DIY enthusiasts this type of flat roofing requires a lot of skill and can be dangerous.

Stainless-Steel for flat Roofing

Whether you are creating a new build or are updating a pre-existing property, metal roofing is an option that appeals to a wide audience. Metal roofing is renowned for its attractive appearance, durability, fire resistance and overall charm, but there can be confusion due to the number of materials available. Some of the more common options include zinc, copper and lead, but each of these have various advantages and disadvantages that usually depend on individual circumstances. One metal flat roofing type that can make a statement is stainless steel.

Stainless steel roofing. Tends to be used more as an industrial roof covering

• Stainless steel is very light.
• Although stainless steel doesn't create a patina like zinc and copper, the chromium in the metal provides a bright high reflective finish- so if you want cool then look no further.
• Little maintenance is required
• Stainless steel is heat resistant in nature. This means it provides an excellent level of fire resistance
• Assuming that the roof is erected with a continuous seam running through it, the use of lightning conductors will be made redundant
• Stainless steel roofs have an extremely long life span
• Can provide an attractive finish

As the list above shows, stainless steel for flat roofing provides a number of advantages over more traditional materials such as tile, lead and asphalt. Whilst this is true a number of these advantages also apply to metals such as zinc and copper. This is why there is often confusion with regards to the type of metal that is best suited for a roof.

Generally speaking metal flat roofing is a good option if you are looking for a light  long lasting, high quality and attractive finish. Copper can be expensive; but wow that patina is wonderful. If you are unsure of where to start, take a look at the pictures and see what floats your boat. All matelic flat roofing systems will be more expensive than other flat roofing types as the material used can be quite costly, and the techniques required to install them are highly skilled. Both of these factors will add to an increased overall cost. However, this should not be viewed in a negative light. The increased cost is also a sign of the increased quality that you are purchasing. A metalic flat roofing system will last for generations, requiring little to no maintenance.

If you like the idea of a metal flat roofing system, but are still unsure as to what type would best suit your needs, then make an enquiry with a professional roofing company. They will be able to provide you with invaluable roofing advice, whilst they will also be able to carry out work in a safe and efficient manner wherever necessary.

 

Image Credits: smaedli, Axelph and furious green cloud

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