Help please with roofing felt spec/standards

[Drain Whisperer]

I volunteer for a charity which has just had a storage shed supplied and installed.
The quotation description for the roof felt was 'Heavy Duty 40kg felt'
I took this to mean 4kg/m2 felt ie 40kg for a 10m x 1m roll which I believe is the accepted way of describing felt weight
The felt installed on the day was 2kg/m2 or '20kg' as I would describe it and I protested this as not meeting the spec.
The supplier (shed supplier not a roofing contractor) has said I am wrong and 40kg refers to the total weight of felt on the roof which, as the shed happens to be 6m x 3m, is indeed just over 40kg including the overlaps.
The supplier also quoted us for a 2.5m x 2m shed with the same 'Heavy Duty 40kg felt' although we ultimately only ordered the larger shed. But I am sure this would not have had 8kg/m2 of felt on it.
They have also said the felt is based on the weight of the roll - I am not sure if they mean that as they use 20m rolls the weight is double the weight of a 10m roll.
I'd appeciate any advice on
a) are they right, in which case I will duly apologise of course
b) is there any 'authoritative' document I could cite to argue that '40kg felt' has a generally accepted meaning of 4kg/m2?
c) is this worth arguing or should I advise the charity to roll over and pay to have the work redone?
Thanks for any help ...

 

[Mottie]

The quotation description for the roof felt was 'Heavy Duty 40kg felt'
I took this to mean 4kg/m2 felt ie 40kg for a 10m x 1m roll which I believe is the accepted way of describing felt weight

I'd say you were right. Everywhere you look, ”40kg" roofing felt tends to be a single roll of 10m x 1m felt weighing 38/40kg

If the quote says they will be using 40kg felt, that would describe the following examples. If the quote says they will be using 40kg of felt then they will be right. Fingers crossed for you.


https://www.rhinobds.co.uk/product/heavy-duty-shed-felt-40kg-green-mineral-1m-x-10m/

https://www.jamessmithfencing.co.uk...fing/roofing-felt/roof-felt-x-10m-green-38kg/

https://www.a1sheds.com/a1-roofing-felt-upgrade-13881-p.asp

https://www.jastimber.co.uk/green-mineral-felt-1e-38kg

https://www.cheshirebuildingsupplies.co.uk/40kg-1e-green-mineral-felt

 

[Drain Whisperer]

Thank you for the very helpful information Mottie. I'll post an update in due course ....

 

[Drain Whisperer]

Update - we reached a financial settlement eventually. The argument that it was the total weight of felt on the roof was not sustainable given that the same weight was quoted for different sizes of roof. The argument that it was 40kg felt because it came in 20m rolls was also difficult to sustain although not quite as clear cut, but as Mottie demonstrated there is substantial evidence that a 'roll' is accepted to be 10m x 1m unless otherwise stated. The supplier's advertising and specs now state 'heavy-duty' not '40kg' Everyone will agree that 'heavy-duty' is fairly meaningless.

 

[Mottie]

Everyone will agree that 'heavy-duty' is fairly meaningless.

True. I’ve never seen anything advertised as 'light duty'!

 

[Notch7]

True. I’ve never seen anything advertised as 'light duty'!

Like coffee…it comes in medium, large, extra large.

never small, medium, large