warm flat roof

[jg61]

Hi Im new here so any help appreciated,
old (at least 12yrs) north facing 8'x12' felt flat roof cracked in places not yet leaked inside?this 'summer'
My plan is to lay 100/ 120 pir foil faced insul over the ex felt, osb over this, then epdm waterproofing. My questions are:
is it ok to use ex felt as vapor check?
can i fix osb through pir into ex deck joists thinking about any probs with restricted expansion? also plan to fill any gaps from top of bwk to underside of warm deck,
Thanks in anticipation jg61
ps sorry if answers in older posts i did do a search first, honest

 

[Mw Roofline]

Can't you take off the felt and the old deck first?

 

[jg61]

Hi yes I could remove old deck just want to leave it if I can I think its solid enough and don't want to damage ceiling with extra work. Any thoughts?
John

 

[SurreyRoofingEstimator]

You can leave the existing as a VCL as long as it is in good order though considering you have cracks and how cheap polythene VCL is you may as well use it too (loose laid) and fix the insulation down with thermally broken fixings (plastic tube washers) and glue the EPDM over the top. you don't need the extra OSB unless you want the surface to be more walkable

 

[jg61]

SRE thanks for that it will need osb on top for window cleaning access can you explain plastic tube detail please can I fix top osb and insulation in one hit with that method thanks john

 

[SurreyRoofingEstimator]

This link shows the tube washers

http://www.fixfast.co/fastener-systems/fr_globaltubewashers.php

though if you are needing to fix OSB then the tube washers won't really be any help and the fixings for the OSB will of course hold down the insulation anyway