Flat Roof Cost Calculator

Flat Roof Cost Calculator

Working out how much it costs for a new flat roof is now even easier than you think!

Using advanced technology Composite Roof Supplies have provided an easy 3 step solution for working out what you need and how much a GRP Roof Kit will cost. 

All you need to know is the Size of your roof! Its as simple as that, no experience is required.

Step 1: Step 1: The roof Length x Width: Enter the length and width in either Metric or imperial measurements.

Tip: if you have an L shaped roof create 2 separate kits just treat them as a square and a rectangle.

Step 2: The Roof edges: The Fibreglass edge trims are really important when the Grp is layed into position, the pre formed edge trim creates not only a nice finish but ensures water can run off the roof into any gutters or prevent water run off in sections where water must be contained. Note: If you have trims already select no trim required. 

The kit builder uses the standard size trims. seen in the section Step 3

Tip: you can add additonal trims or slighty different size trims within the shop section of the website here 

Fibreglass trims come in 3 different sizes the sizes below are excluded from the Flat Roof Calcualtor but can be purchased seperatley 

A170 drip trim – The smallest size of the dedicated drip trims, the dimensions are : Length 3m – Drop 65mm – Flange > 80mm – Roll 10mm - Compatible with the B230 raised edge trim

B230 raised edge trim – The smallest of the dedicated raised edge trims, the dimensions are : Length 3m – Visible face 105mm – Flange > 100mm – Roll 10mm

A250 drip trim – The largest of the drip trims, the dimensions are : Length 3m – Drop 140mm – Flange > 80mm – Roll 10mm - Compatible with the B300 raised edge trim

B300 raised edge trim–  The largest of the raised edge trims, the dimensions are : Length 3m – Visible face 175mm – Flange > 100mm – Roll 15mm

Fibreglass Trims Glossary

Kit builder Trim sizes:

A200 drip trim – The mid size of the drip trims, the sizes are : Length 3m – Drop 90mm – Flange > 80mm – Roll 10mm Compatible with the B260 raised edge trim

B260 raised edge trim– The mid size raised edge trim, the sizes are : Length 3m – Visible face 125mm – Flange > 100mm – Roll 10mm

Wall Edge - universal and has a flange of 100mm or 75mm - overal visible sections - 100mm x 25mm x 75mm - Overall height up the wall from the deck boards 125mm or 95mm

Flat Slope Trim - 300mm flat trim supplies rolled up up to 20metre pieces

Parapet Edges - 75mm x 105mm - internal or external 

Expansion Trim - used on roof over 50m2 or to join to roofs together like a felt garage and a new GRP Roof 

grp roof trim types

Step 3: Congratulations your GRP Kit is complete! you can add extras in the last step such as:

Premium 600gsm Chopped Strand Matting

Upgrade from the standard 450gsm (Includes extra Resin and Hardener)

Pre-formed Corners

Upgrade to pre-formed corners rather than fabricating your own with bandage. Includes 2x C1 External Corner

Anti-Slip Grit For Balconies

Added to create a non-slip topcoat

GRP Installation Tool Kit

Everything you'll need to fit your kit! Dispenser Bottle, Paddle Rollers, Roller Sets with Extending Pole, Buckets, Paint Brushes and Disposable Gloves


Dark Grey Topcoat (RAL 7021) 
Matting, Bandages, Resin & Catalyst Hardener (plus Acetone for cleaning surfaces and tools)


GRP Trims, PU Trim Adhesive & Clout Nails

Installation Guide

Your companion for fitting your new roof 

Now you have everything you need to complete a Fibreglass Roof, you have 2 options Save the kit for later or add to basket TRY IT CLICK HERE