SBS New Cap Sheet over Old SBS Cap Sheet


To properly seal, the silicon needs to be in thick even costs to form a barrier. The granular spec you are looking at requiring a second coat is most likely just to stick the granuals. If you put the granuals in the first coat I think you works defeat the purpose of the silicon all together. The spec you are looking at is most likely for creating a safe place to walk on a flat roof, not for aesthetics. I don’t think you are going to get a surface that looks anything like a granular cap sheet by embedding granuals in silicon epically after rain washes of excess. Don’t know how big your roof is but at 30# of granuals a sq and an extra cost of silicon the price keeps climbing.

If it was my house and I really didn’t want to tear the roof off for some reason, which I would never do, I would cement and nail new metal edge over the old one, coat the whole mess with asphalt primer and torch new cap over whole thing


good advise.asphalt primer and id mop it on.but I’m old school.


DECISION: Not doing silicone. Slippery characteristic is unacceptable.

Not sure what you’re suggesting… do you mean, primer, mop adhesive, cap sheet?


Yes that would basically leave you with 3 ply stsyem, base, cap, cap.


A Second Thought on the Silicone Slipperiness:

When it gets dirty with junk from trees, is it still slippery?

My roofing contractor friend likes the idea of the silicone durability and said we shouldn’t be up on the roof after the job is done.

So I’m reconsidering the Silicone. (He said sprinkle a little sand on it around the edges if concerned.)


I’ve made my decision: Gaco Roof (all quantities per square)

1.5 gal to cover the cap sheet
1.0 gal 2nd coat
Broadcast 10-20# granules on 2nd coat while still wet

Did get warning from Gaco rep: DO NOT apply more than 1.5 gal since that will interfere with solvent dissipation and will crack. NOTE: The Henry stuff is OK for >50 wet mils which is impressive. Their butter grade is OK to 1/4" and their fibered to 1/2" which will stick to verticals too.