Is GRP a good roofing material?

GRP flat roofing Prose and cons


  • Now easily available in DIY shops
  • Good and strong
  • Tested over many ears to perform
  • Comes in any colour
  • Can be formed into any shape
  • Will hold standing water


  • Very rigid and brittle if laid to thin
  • Has to be laid by experienced people
  • Has to be built up to form a good surface and this takes time and materials
  • Weather and temperature dependable

Other options to consider

  • 3M SD650
  • GacoRoof
  • Kemper

All three are based on the principles of GRP resins and glass fiber but they have been modified to be flexible.

My opinion.

If the GRP roof is laid correctly and to the correct depth they are good roofs however I only ever see well laid GRP roofs when Im down the coats these are normally laid by boat builders and are formed from may layers of GRP,  forming a good strong shell.

If you have lots of money and want a really nice looking roof then GRP is the way to go.


Flat roof survey or report

It’s not often we get asked to look at a flat roof as large as this and unfortunately our free estimate wont cover the cost of surveying this roof and reporting back the findings.

This flat roof is a round 1500m2 and is covered with an old type flat roofing membrane with welded joints, this type of roof is still being fitted but we consider it to be one of the older generation flat roofing materials.

I’ve taken a walk around the inside of he building and seen where the water is penetrating, externally I have examined the roof and can see lots of  design faults, I will be submitting a preliminary report  suggesting that thermal imaging of the roof is undertaken to show where the insulation is saturated this will help identify the areas of the roof where the roof has taken on water, then we can  scrutinise each joint and visually inspect the membrane for holes punchers  or rips.

At this stage I think we will be cutting out all the wet insulation then repairing the roof using a liquid roofing systems such as GacoRoof.

Related articles

Leaking pipe rots timbers of flat roof

Maintenance of pipes, guttering roofing gullies were all general items that had to be looked at cleaned and maintained on a regular basis thought the year when I first started working on properties.

Unfortunately  with the cutbacks and the lack of intrest some people have in there property these things just dont get maintained.

Have a look at this videio the pipe had been leaking fr some time now the customer has to pay out for repaointing of the walls and a complete new flat roof

The old flat roof will need to be completely removed all the timber joists that are supporting the roof will need striping out and renewing, unfortunately for he customer the insurance company have declined the claim on the bases that this was forceable

We find that the best policy to have when managing a large block of flat is to have a good routine  maintenance schedule. When It come to making claims on the insurance of the block, being able to prove that maintenance was kept up can be an advantage.

Liquid roof covering by GacoRoof over a parapet wall

In this video I show you just how flexible the GacoRoof covering is

We have just covered an old asphalt roof in wembley with the new liquid waterproofing system, we dressed the parapet walls with the system so we didn’t have any flashing details to deal with.

No flashing no messing about complete encapsulation, the flexible roofing system will allow for expansion and contraction  over the seasons





Parapet wall and flat roof before and after


Using a liquid roofing system we can encapsulate the parapet walls with ease


Take this old asphalt roof in Wembley, the asphalt has sagged and cracked away from the parapet wall


Cracking is evident and the ceiling below shows water-damage.


The brick parapet wall is  solid construction but the flat roof is built on timber and will settle over time, the asphalt will melt in the summer and go brittle in the winter, with the thermal movement the  cracking occurs.


So after cleaning of the roof taped patches are applied to the cracks before the new roofing system is installed to the roof.



On this roof we are using the GacoRoof a silicon-based liquid roofing materials from the USA . GacoRoof is very flexible and can withstand   the movement described above.


The other interesting factor to all of this is the color of the finished roofing materials GacoRoof  has a white finish and reflects the sun’s heat stopping the  old roof from melting


liquid flat roof gacoroof london 14



Preparation before a new liquid flat roof

We are on day to of this roof, the old roof is an old asphalt roof and was leaking from several places.

In this video I walk you around the roof showing you the condition of the old roof, some of the cracks and detailing.

The new liquid roofing system we are about to use on this roof is imported from the USA and is relatively new to the UK

It’s a silicon-based flat roofing materials called GacoRoof and one of its biggest advantages over other flat roofing materials is its amazing flexibility

Before we cover the old flat roof with the new roofing system we have given it a good clean and repaired all the damage that has happened over the years.

This old roof had Ponding or pooling water all down the center, although a problem to the old roof its not a problem to the new liquid silicon roof.

Problem with Green flat roof

Green flat roofs may be nice on the environment and nice to look at but when you get a problem they can be very expensive.

This green flat roof is probably going to have to be completely striped as the flat roofing membrane under it is leaking somewhere and we cannot find the problem.

Realistically under a green flat roof you don’t want to have joints that can go wrong at sometime, most new flat roofing materials will last for many years but when they do go wrong they will alway go wrong where there is details.

Remove the details remove the problem.

liquid rubber SD650 By 3m flat roofing 8