Is '90 pound cap' the same as 90 pound felt

Hello Everyone,

I am in the process of getting estimates on a new roof. I currently live in a townhouse (quad) and all 4 owners have agreed to get a new roof. My portion currently has silver coating, the other three have roof roll. Our roof is flat, which makes it worse. So there is ponding water after it rains and around the AC unit. Anyway …

One roofer wanted to put a thermoplastic membrane - which I hear (from another roofer) that it doesn’t hold up very well in the Florida heat and I would get 5 yrs max out of it.
Two others mentioned a cap sheet that I believe they called ponding spec - meant for ponding issues. Which sounds like what I want.
The fourth -who happens to be a friend of one of the homeowners in my quad, put this in his proposal:

[size=100]“All roofing will be removed and the sheeting will be renailed to code specs and will be inspected then 70-lb. felt will be applied tin-tagged to code specs and inspected again then single glass ply will be laid (just like what you have on right now) then a cap sheet will be applied using the hot mop process.”[/size]
and later explained [size=100]“Cap sheet is 90-lb. sheet that must he laid by the hot mop process”[/size]

My question is: Is 90-lb. cap sheet the same thing as 90-lb. felt roof roll, or is more like modified? This is going to determine if he is a possible candidate because I have heard over and over that 90-lb. felt should not be on flat roof systems because it doesn’t do well with standing water.

I just want to make an educated decision. Any input would be greatly appreciated!


In my area referring to 90# means 90# rolled roofing, complete and utter garbage.

Go with the roofers that speced the thermoplastic, it is much better.

Axiom - Thanks!

That’s what I was afraid of. I just wanted to make sure that those terms weren’t two different things.
So you think thermoplastic will hold up to S Florida heat? In your opinion, what do you think the life of it would be vs. having a BUR with a ‘ponding spec’ cap?

I was tempted to just put another silver coat on but I bought this place two yrs ago, and the owner at the time had just fixed a leak, and now I’ve had a couple - and I have blisters around the AC unit. I don’t really have a good history of the roof, supposedly it was “replaced” 10 yrs ago along with the neighbors but they both have two different coverings, which leaves me to question the age of the roof. And sense all four owners are willing to be in on it, I figure I’d take that opportunity and just do it.

(I’ve patched two leaks myself just to buy time. I hate to say it, but sometimes I think roofers think they’ve got an easy target because I’m a woman who, more than likely, won’t know the difference, you know?). Anyhow, thanks again for your prompt reply!

PS (I guess I do need a signature, ‘cuz I’m not a freakin’ roofer, :D)

A PVC membrane should work just fine in Florida, TPO also.

It sounds like you have some roofers trying to push what they like rather than what your home needs.
This is not necessarily a bad thing, they like what they like for a reason.

A 90lb Awa plan is a decent product IMO.But with your very harsh heat and humidity it would be last on my list.Lowes and Home depot sell some junk $22 per roll.The product I am speaking of is around $150 per roll.

thanks guys.

The roofer just clarified that the cap will be modified bitumen.

So I just need to consult with the other three units and make a decision. Thanks for all your input fellows!


Mopping a base ply and a modified cap is a good roof in most cases but i have seen many sbs modifieds fail prematurally in ponding water,they do not hold up well in these cases.I would be brand specfic and ask app or sbs, Tpo is the popular flat roof covering of the Decade some have no problem with standing warrant also.

Dana, regarding the membrane: There is a product made by Firestone called TPO which comes with a 20-year manufacturer warranty. The contractor however must be a certified installer.
As to the cap sheet, there is a 72# which is granulated cap sheet, embedded in asphalt. Then there is a modified cap sheet. You are fine with the 72# granulated cap sheet in the field. We highly recommend modified cap sheet along perimeter (edgement) for all roof-to-wall intersecting and flashings.


So, it looks like I am leaning towards a pvc covering/IB Roof system. From what I’ve been quoted, the warranties that I have been offered on the modified and pvc have been the same (10 yrs) just waiting on estimate for the pvc. plus I was told that it has an energy star rating and Florida Power & Light (utilites provider in FL) provides a rebate - a certain $ amount per square foot. Seeing that it isn’t porous, I think it might be the better alternative depending on the estimate I get. If the cost is within the same range as the modified, seeing that the warranty amount is the same, there is nothing to lose with the pvc.