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1. Thermadeck is the insulated version of Permadeck20

2. Ideal for THERMALLY UPGRADING flat roofs with poor or no insulation

3. Uses the existing roof as the lower layers of a modern ‘warm roof’ design

4. Saves disturbing the inside of the building

5. Cost effective: reduces heating costs, renews waterproofing and adds to property value

6. Efficient: most domestic work completed in ONE day

7. Can be grant assisted for qualifying applicants

If your house extension or dormer was built in the ‘50s,  ‘60s or ‘70s this is probably how it was made, there might even be NO INSULATION AT ALL:



Tapered firring


Thin glass wool insulation


This old design no longer complies with the Building Regulations and because of its poor insulation level can cost you far more to heat than a modern roof.     

Does your room feel cold or damp?    Is it hard to heat and quickly cools down?

Fit a THERMADECK®  ...

Existing roof tidied and retained

New layers of THERMADECK®:

Permadeck on ply on insulation

See NOTES below.

THERMADECK comes in two standard grades, though we can vary the specification to suit unusual existing roofs:

THERMADECK 20/75:     50mm PUR insulation, 12mm ext wbp plywood, Permadeck 20. U-value depends on existing roof.

THERMADECK 20/120:   120mm PUR insulation, 18mm ext wbp plywood, Permadeck 20. U-value = 0.18

Both systems come with a 20 year Permadeck guarantee and may qualify for the new Green Deal, see:


1. THERMADECK adds to the height of the roof so fascias and gutters (if any) may need to be modified.  

2. 100mm PUR insulation is roughly equivalent to 200mm of glass wool.  

3. THERMADECK can be used as a balcony surface.

THERMADECK® transformed this poorly insulated sun lounge.

THERMADECK® quadrupled the insulation levels on this scheme of 1970s architect designed homes.

Existing roof


This B&B in Mull has a stunning view and a great THERMADECK®.

It will now be cooler in the summer and warmer in the winter.

If your roof has no insulation then its U-value will be about 1.25, so Thermadeck, at 0.18, is 7x better. In other words your old roof loses heat 7x faster than your new Thermadeck.