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.


Why choose a liquid flat roofing system for your new flat roof.

Some roofs just look a mess when covered with a sheet roofing materials, if the flat roof is large and the detailing is limited then a sheet flat roofing materials such as EPDM rubber could be used.

If the roof is covered with obstacles such as skylights, pipes, air conditioning units and so on then a liquid roofing system should be chosen.

I alway explain to my customers we don’t choose the flat roofing system for the roof the roof and your budget chooses the system.

The new Liquid roofing system we are using on this roof is ideal as an overlay system for old flat roofs, the advantages of the GacoRoof liquid flatroofing system is that its snow white when completed reflecting all the suns rays int he summer.

EPDM rubber roof inspection

Around five years ago we laid this flat roof using EPDM rubber over tapered insulation, the job was quite complicated as we had to adjust the falls to the original flat roof so all the water would run to the back of the roof. The roof insulation was laid at the front of the roof to a depth of around 350mm, pushing the water to the back of the roof .

I also show you in this video some of the characteristics of EPDM rubber. EPDM rubber is flexible and when laid over soft insulation the completed roof is soft to walk on. Customers sometimes comment on this as if it’s a problem, however it’s not! That’s how it’s designed to be. The complete system is lightweight and designed to go over the top of other roof coverings such as felt and asphalt.

EPDM rubber roof W13, West Ealing

Via Flickr:
EPDM rubber dressed over the top of new insulation to Part L of the building regulations, the EPDM rubber looks good dressed up over these parapet wall and around the chimney pots.
This EPDM rubber flat roof looks good and the area to the chimney pots dressed in EPDM solved a big problem. We laid this roof over insulation supplied by Kingspan insulation,
EPDM rubber roofing material should be trouble free for between 20 to 40 years. The EPDM we used on this roof comes with a 20 year insurances back guarantee and is expected to last for up to 40 years, there are different EPDM rubbers on the market, and they all come with different guarantees, we are trained installers of three different EPDM rubbers some come in small sheets and some come in large sheets, depending on the flat roof what we are to lay the roof over, depends on what EPDM rubber waterproofing membrane we use. Please contact us at London Flat Roofing or call 020 8421 3193 for more information. All comments are welcome so please leave some feedback if you find the information we supply helpful.

Green mineral felt flat roof

Realistically old mineral felt roofs have to be a thing of the past now.We need to install a new flat roof as this roof is still leaking after it has been repaired

There are lots of new flat roofing materials on the market, such as EPDM and the new 3M SD650, same day roof system.

We need to install a new flat roof as this roof is still leaking after it has been repairedYou can see on this photo that the owner of the property has been trying to fix this old flat roof by applying some sort of liquid sealer to the joints of the felt.

New flat roofing materials dont have joints, EPDM comes in large sheets and the new liquid applied flat roofing materials don’t have any joints at all.

We need to install a new flat roof as this roof is still leaking after it has been repaired

Making the flashings out of the new flat roof materials is also easy. Unlike the old flat roofing materials, the new materials are alway flexible and the flashings can easily be formed from the same materials and fixed to any wall.

Detailing round pipes and skylights is also very easy especially using the new liquid flat roof systems

If you need more information about flat roofing please don’t hesitate to contact me at London Flat Roofing.

We need to install a new flat roof as this roof is still leaking after it has been repairedI

Flat roof decking OSB v Ply

Flat  roof decking in old roofs used to be like floor bards and was called a close boarded roof deck.Decking for flat roofs made out of timber

Along came chipboard and in the 70,s flat roofs were laid using this, not very good as  when the roofs leaked the chipboard got soggy and the roof collapsed.

This is an old video I did some years ago showing a collapsed chipboard roof

Straw board or stramit board  used for flat roof decking

They moved away from this and started using a new product call  Stramit board or strawboard, this was some sort of straw mixed with cement and formed

into sheets it offered strength and insulation all in one. Realistically nothing wrong with it, I still come across flat roofs with it in and providing its been installed  with plenty of support it’s still performers ok  as a roof decking. The problem is that the roofer wold bond the old felt to it and when we remove the old felt we rip it to places .We replaced some garage roofs at Hampton Court Palace  around two years ago, the old roof decking we removed was stramit board and this video shows us removing the old decking, note we replaced the roof using EPDM rubber.
So ply came on the market and lots of roof decking were laid using shuttering ply, now shuttering ply has a tendency to rot if it gets wet  so some specification request we use WBP ply Exterior grade plywood (WBP – Weather and Boil Proof
This ply has recently come down in price and also in quality I have seen some of this plywood laminate with the smallest amount of damp getting to it!
OSB has now hit the market and is being specified by most  architects roofing materials suppliers as the substrate to use when replacing the decking to a new flat roof or doing a retrofit flat roof.
Personally we like it  we tend to go for the more expensive T+G sheets as these  are easer to lay and support  the roof better  when butting the bards together .

Problems with lead roofs

In this new video I show some problems that I see more and more, the lead is oxidising because of lack of ventilation.

Todays building methods and materials mean that if you don’t ventilate your roof correctly the roofing membrane will stop all movement of air and water vapor this can then lead to sweating when the conditions are correct.

The new EPDM rubbers and some of the liquid rubbers are vapour permeable however this does not mean you don’t have to vent the roof it just means that a small amount of water vapor can move through the membrane