Garage Roof Felt Replacement Quote Advise

bloke91

Hi all,

I have a single garage felt roof I have had a couple of quotes to replace the bitumen felt flat roof 4m x 4m with Firestone rubber with aluminium stands , wall trips and drips etc.

The quotes suggest over boarding existing bitumen felt which is in intact and sound and further overboard with 11 mm OSB fibre board.

Quotes are around £2500 with guarantee from well respected roofers with great reviews on the web, Facebook and check a trade etc.

Is it ok overboard existing bitumen felt, any risks or down sides of doing this?  FYI, My garage roof boards are in sound condition with no leaks etc.  

Thanks in advance your assistance.

grumpy_codger

What's the purpose of overboarding? If the roof is flat, IMO overboarding makes sense to create a small slope/pitch.

And what's "OSB fibre board"?

OSB = Oriented Strand Board (no fibres)

bloke91

Quote indicates fully overboard existing bitumen felt leaving bitumen felt intact over boarding with 11 mm OSB fibre board.

I am told the roof and decking is solid and 100% dry, no current or sign or previous water leaks, soft spots.

Hope that helps.

grumpy_codger

Well, you are the customer and you pay your money. Don't trust any "great reviews on the web, Facebook and check a trade etc." 

Ask the "well respected roofers" what "OSB fibre board" is and why it is needed. I'm not a roofer, but I know two different products - OSB and Fibre Board. 

IMO, if the existing felt is failing, it needs removing and replacing - like the quotes say - "to replace". There is no point in keeping it under some boards. And if the "garage roof boards are in sound condition", IMO no overboarding is needed unless for creating a slope like I suggested above.

Veteransaver

Surprised they are leaving the old felt in place. Maybe they don't want to dispose of it? 
If the old felt is failing then I would be surprised also if the wooden boarding isn't failing too. I'd be concerned it would continue to rot of it is overlaid with rubber and any moisture within it can't escape.

tetrarch

I'm not sure that bitumen felt is the best thing to overlay EPDM onto. Personally, I'd want the felt removed and and reboarded to give a completely flat surface for the EPDM to be then glued onto

Regards

Tet

Albermarle

If the current felt is ‘intact and sound’ it begs the question as to why you are wanting the work done in the first place?

EssexExile

I assume just covering what's there is easier and cheaper than stripping the existing felt off and getting the surface smooth enough to lay the rubber on. I don't see any downsides although, like the post above, I wonder why you want to replace a perfectly functional roof.