Flat roof repairs

A flat roof refers to a roof that is almost or completely level. Simply put, Flat roofs are what they are. Flat. But though they are termed as flat, most flat roofs are typically designed to have a small fall to ensure rainwater can run off towards the lower side. Although flat roofs are mostly used in warm climate countries, its popularity has spread all over the world with each area having its own specific design and set of materials to function better in that climate region.

Flat roofs can last from 10 to 35 years depending on the type and quality of the material and structure. As the roof is one of the most critical parts of the house, it is important to monitor and assess your flat roof occasionally to quickly identify any potential problems for repairs and replacement. Some signs to look out for are:

Frequent Leaking

When leaks start, they are basically letting you know that something is not right up there. Seeing dark streaks indicate that water is seeping into the building and the occasional drip from the ceiling is a strong indicator as well. Broken seals around pipes or under the flashing can also cause leaks.

Growing Moss

especially large amounts of it on the outside of the roof is a sign that your roof needs some repairs. The moss forces the tiles apart and causes water to leak through into your house. The moss can be taken care off with a chemical treatment to kill it.

Ponding / Pooling

Ponding is the largest issue associated with flat roofs. Ponding makes the roof membrane weak which leads to leaking and cracking. If pools of water regularly develop on your roof then it is time to consider replacing your flat roof.

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Types of Flat Roofs and How To Repair Them


An asphalt roof is made up of a base material which is covered with a layer of asphalt or modified bitumen with trace elements of mineral granules. Asphalt roofs are beautiful and inexpensive to install. They do however come with their cons such as shrinkage, cracks and splits, asphalt blisters.

With little roof damage by cracks and blisters, a simple DIY repair is possible using waterproof paint over the damaged area and this works very well. There are three types of waterproof paint which are commonly used. Bitumen based, acrylic based and rubber based waterproof paint. Professionals mostly prefer acrylic based waterproof paints as they are less messy working with than the other types and do give a beautiful look of the roof in the process. Large area damage will need more than a simple DIY patchwork and is better to enlist a professional. A professional will put on a layer of thick high performance felt or torched on roofing felt after dealing with the cracks and blisters. This type of repair is called layer on top and adds more life to your roof as it is relatively permanent to the temporary small patchwork.



A concrete roof is simply a solid slab of concrete covering the top of your house. Most concrete roofs are several inches thick though exact specifications vary based on design, preference and cost.

Common problems associated with concrete roofs are cracks and splits in the concrete and surface wear. A crack in the concrete can lead to a leak but the next problem is finding the crack within the concrete which can prove annoyingly difficult. Surface wear although not likely to cause leaks can be a hindrance to repairs. Surface wear has a withering look with flaking on the surface of the concrete and sometimes growing moss. With difficult to find cracks, repairs can be done with waterproof paint. Bitumen based waterproof paint is best and DIY handy. The surface wear is dealt with first if there is any. Cleaned of any moss and cleared of loose chippings which is then allowed to dry thoroughly before the paint is applied over the cracks. A layer on top repair can also be done if the crack is obvious and has little to no surface wear. The layer on top repair is best done by a professional.



Ethylene Propylene Diene Monomer or EPDM for short, is a synthetic rubber roof membrane which is extremely durable. The cost of an EPDM roof is considerably favourable when compared to other types of roofs.

Being virtually waterproof and fire resistant EPDM roofs are quite the durable foe against the elements. Lifespan can be up to 50 years or even longer when maintained properly. Leaks do occur over time though EPDM roofs are waterproof but when a leaks develop, repairs are not difficult, they are easy, affordable and fast. Cuts and tears of the rubber are also DIY friendly to fix if the area of damaged is small. A small tube of lap sealant can be applied to the damaged area for a simple temporary fix. A more permanent fix will be the use of a self-adhesive flashing to make a simple patch over the damaged areas. A rubber flashing tape is best after cleaning the damaged area and applying an EPDM primer.



This type of roof is one of the most popular flat roofing types in the UK. It is a composite material which has fine fibres made of glass and used to strengthen plastic. GRP stands for Glass Reinforced Polyester.

Being very easy to repair is one of the appeals of fiberglass roofs. Common problems associated with fibreglass roofs are cracks and splits near board joints, trims or upstands and leaks near abutting walls. Cracks are caused by the lack of reinforcing on the joints and trims leading to expansion and contraction. Sometimes not allowing for expansion in the planning stage are also causes of cracks in the fibreglass. This can be repaired easily with a temporary fix by applying an acrylic sealant on the affected areas after the roof is cleared and cleaned of dirt. A more permanent fix will involve cleaning and sanding the affected area with acetone and 60 grade grit paper. A CSM (Chopped Strand Mat) can then be laminated into place.



Felt roof, sometimes called roofing felt underlayment or roofing tar paper is a protective layer installed under roof tiles. This method has been in use for over 100 years and was initially used as a temporary waterproof roof whilst the actual roof was being built.

Splits, tears and blisters are common problems associated with felt roofs. Repairing damaged areas of a roof felt is not that difficult a task. Damaged areas must be cleaned and left to dry or a heat gun can be used to dry the area faster. A new felt patch can be placed over the damaged area after it has been cut out with some bitumen adhesive to strengthen the new patch layer.


Our Guaranteed Service

BIM is the No.1 professional roofing construction company in London. We have highly skilled roof repair specialists who employ the best quality grade roofing materials for any roofing project. Our service is perfection guaranteed as we strive to give our customers the very best they deserve. When roof repairs get too complicated for simple DIY tasks, BIM brings an effective and efficient roof repair service to your project. All at affordable rates, so you don’t have to worry at spending too much on repairs. From asphalt roofing to concrete roofs and EPDM rubber roofs, we handle them all and more. No matter which roof type you have, we will ensure the very best of roof repairs.

Matt HAuthor: Matt Holder

Matt Holder is our in-house writer. Matt has been working in the construction industry for 10 years. From working on-site to integration himself into our office.


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