Insulation for Flat Roof

[SouthHams]

Hi
I have a shallow (3 degree) pitched roof covering about 150 m2. The roof is felt over marine ply and is in reasonable condition considering it was fitted in 1987. My problem is that in 1987 2 inches of insulation was all that was required. I would therefore like to add additional insulation. But how without removing the roof or the ceilings?

The gap varies between about 150 to 450 mm across the width of the roof.

Are there any blown options that might work?

Any suggestions appreciated

 

[Xenon]

Another 70 mm on top of your existing roof and felt over.

 

[SouthHams]

Another 70 mm on top of your existing roof and felt over.

Thanks
Any suggestions for the best/most cost effective covering to use?

 

[catlad]

You have a flat felt roof that is still going strong after 25 yrs. The modern felts are more elasticated less prone to splitting so I would say use felt again.

 

[SouthHams]

You have a flat felt roof that is still going strong after 25 yrs. The modern felts are more elasticated less prone to splitting so I would say use felt again.

I'm being offered £26K to cover the roof with 100mm insulation and Sarnafil.

Is this a good deal?

Would felt be a lot cheaper?