Commercial & Industrial Roofing FAQs – Cheshire & North West

A: The FLAT ROOF COATINGS LAVA 20 PU Coating system can be used in a variety of applications including new builds or the refurbishment of all types of flat roofing, balconies, terraces, walkways, car parks, podium deck, wet rooms and more.

The moisture-curing aspect of a polyurethane coating refers to the chemical reaction that takes place between the coating and moisture in the air and on the surface of the substrate. This reaction is known as a polyaddition reaction and involves the reaction of an isocyanate functional group with a hydroxyl functional group to form a urethane linkage.

In a moisture-cured polyurethane coating, the isocyanate and hydroxyl groups are present in the same molecule, which allows the coating to react with moisture in the air and on the substrate without the need for a separate curing agent or catalyst.

When the coating is applied to a roof surface, it begins to absorb moisture from the air and from any residual moisture on the surface of the substrate. This triggers the polyaddition reaction and causes the coating to crosslink and cure from a liquid to flexible, hard, durable, and waterproof film.

The curing process can take several hours to several days, depending on the temperature, humidity, and thickness of the coating. During this time, the coating will continue to absorb moisture and cure until it reaches its final properties.

One advantage of a moisture-cured polyurethane coating is that it can cure at ambient temperatures and does not require heat or additional curing agents, which simplifies the application process and reduces the risk of curing issues.

However, it is important to note that the presence of moisture is crucial for the curing process to occur, and excessive moisture can lead to over-curing or blistering. Therefore, it is important to follow the manufacturer's recommendations for application and cure conditions to ensure optimal performance and longevity of the coating.

A: Protection From Rain And Snow – Your finished roof should have a slope of at least 1 in 80 and should drain to one or two edges. It’s best to use conventional eaves gutters rather than internal outlets. If you do use internal outlets, make sure they are big enough to deal with storm conditions and are fitted with leaf and gravel guards. The waterproofing should extend up adjacent walls at least 150 mm (6 ins) from the roof surface in all situations.

Protection From Sun And Frost – It pays to insulate. Your heating bills are lower in winter and your rooms are cooler in the summer. Don’t forget any insulation of a new flat roof must satisfy Part L of the Building Regulations.

Protection From Condensation - If you have a cold roof it’s essential you include adequate through-ventilation.

Protection From The Wind – Your roof should be able to resist wind forces and an experienced contractor should be able to advise you. Make sure you ask for advice if your roof is particularly exposed.

Protection From People – The materials you choose should suit the roof usage. If the use is changed, you might have to strengthen the structure.

Protection From Fire - Don’t forget to consult your local authority if you are planning a new flat roof.

A: Don’t worry your new coating will be fine as it is moisture cured (this means it dries even under water).

A: If it’s obvious what’s caused the leak, and the rest of the roof is okay, then a minor repair is probably okay. This sort of random patching up isn’t guaranteed though. That said, if the whole roof is in poor condition, or you need a warranty, then a full replacement (or possibly an ‘overlay’ – see below) is the best thing to do.

A: Speak to us, we may have preferred and registered roofers that cover your area. Also, asking around for local roofers with a good reputation in your area is a good place to start, ensuring they are members of the appropriate trade association.

A: Flat roofs are generally built with a slight incline so that rainwater can drain away into the gutters. Basically, flat roofs aren’t always absolutely flat.

A: In many cases the existing roof is sound, and the membrane is simply getting old. If so, the contractor might advise you not to expose the building structure to the elements while they strip off the old membranes. Instead, you leave them in place to act as a base layer for a new system. This is known as overlaying the roof. As long as there are no other problems such as condensation or damaged decking, then overlaying is perfectly acceptable. There are a number of products available on the market you can use.

A: Not unless it is leaking or showing other signs of damage. If and when you do have it replaced, you should tell the contractor so they can check the cause of the ponding and itemise the cost of dealing with it in their estimate.

A: The deck of your roof is the layer of plywood or OSB 3, which goes over the joists to support the insulation and membranes. Where this is damaged or is a part of the waterproofing system, you’ll need to replace it. This is known as re-decking. The contractor should be able to give you a price for the work.

A: Unless the contractor was told about the ponding, they are unlikely to have quoted for changing the falls. This would have meant removing the decking, placing firring pieces (wedge-shaped timber strips) on the joists, and re-fixing the old deck or a brand new one, before installing the new waterproofing system. This could have doubled the cost of the job. The decking might have deteriorated and sagged between the joists, in which case it should ideally have been replaced.