Replacing the roof

[Squeeto]

With a new roof, what is the best way to deal with the gap on a fiberglass end cap?
I need an adhesive sealant that can also give some rigidity to support the cap trim and stick to a plasticized roof membrane.
You can see the depression of the screw hole from a prior install.

The edge of the fiberglass does align with a truss so that is a good thing. I will make sure not to over-tighten.

I am considering something like 3M's 4000 sealant for plastic. Is there a better product for this application?
Thank you.

 

[Gary RV_Wizard]

How close in height will the adjoining surfaces be once you lay on the new roof? Typically the roof membrane (EPDM or TPO) or filon (fiberglass) will extend a bit under the cap. They you use a sealant with a high stretch factor because in near all RVs that joint is subject to a lot of movement stress. Some owners cover the seam with roof tape (e.g. Eternabond) after sealing, for some extra protection. Most RV-use sealants offer a lot of stretch along with a excellent adhesion.

 

[Squeeto]

How close in height ..

Up to 3/16" in places with roof membrane tucked under.
I have managed to clean out about 1.5" under the fiberglass.
I was hoping for a sealant that has some rigidity too so that the screws can be tight without flexing the fiberglass.

 

[Gary RV_Wizard]

Just remember that the cap seam is gonna move no matter what. The RV body will twist & flex enough to guarantee that, so use sealants that can accommodate it.

 

[Squeeto]

How do you feel about Sikaflex 291 and would you do the extra cleaner, activator, and primer or will a good scuff do?

 

[Gary RV_Wizard]

I don't have any experience with the 291 product but Sikaflex is a top quality brand. I've used their glass to metal sealants several times.