About This Flat Roof Calculator
Each year we contact dozens of flat roofing specialists and ask them to provide us with a price for replacing a flat roof.
The prices displayed on this calculator are based upon the responses we receive.
We’ve included VAT at 20% but you might not be charged this tax if your chosen flat roof specialist is trading below the VAT earnings threshold.
Use this flat roof calculator as a general guide to flat roof prices in the United Kingdom.
Other Costs to Consider:
You may wish to replace any fascias and soffits around your flat roof with new Upvc plastic or paint any existing timber ones. You may wish to replace any guttering to the edge of the flat roof.
Every flat roof project is different and the prices displayed on this flat roof calculator may not reflect the true cost of your flat roof project. We urge you to get a fixed written quote from a local flat roof specialist.
What is Bitumen Flat Roof Felt?
This flat roof calculator is for bitumen-based felts which have been in use for decades and are one of the oldest and most trusted roof materials. Bitumen is made from extremely sticky liquids that harden when cooled to form a waterproof layer.
Is Bitumen The Best Felt For My Roof?
Bitumen based felts are considered a good all-rounder and are suited to large areas where water is allowed to run off and doesn’t pool. For roofs where water pools, we recommend a one-piece seamless waterproof covering such as rubber instead of bitumen.
How Long Does a Bitumen Flat Roof Last?
A 3-layer bitumen flat roof should last in excess of 25 years if laid correctly.
Are There Any Alternatives to Bitumen Felt?
Rubber and fibreglass are the most popular alternatives to bitumen-based flat roof felts. Rubber is a good all-rounder while fibreglass is best suited to smaller roofs no larger than a double garage.
How Long Does it Take to Replace a Felted Flat Roof?
A single garage will take around half a day, or three-quarters of a day if the decking needs replacing. A double garage will take around a day or just over a day with the decking being replaced.