Do I need both?

I want to use GAF’s Liberty self-adhesive mod bit. on my flat roof. The Home Depot ‘experts’ couldn’t confirm whether or not I needed a base sheet in addition to the cap sheet. They seem to think the cap sheet was all I needed. This is fine if they are correct. Are they?

no they are not. buy the base sheet. follow the instructions and you will survive.

Thats why its called a cap sheet. Its a two part system

Base 4-sure :smiley:


Finish this job and you could be a manager at Home Depot.

Make sure you use an SA base sheet and not a hot base.
nailable or SA base. I don’t know if this is proper, but I have had a few guys tell me they use Ice and Water shield as the base on SA’s. They say it seems to stick better and haven’t experienced any bubbles like you sometime see with SA’s.;

i would think the cap sheet wouldnt stick to ice & water shield well. especially if its granular surfaced.

One of our local residential roofing companies uses Grace for their base sheet for SA modified.
They say it is working well for them with no issues.

While some of their methods are different from mine they are very good reputable roofers.

I have heard of guys sticking the cap right to new, clean plywood. I would not do it. Nailbase and cap sheet. You can also do a mid ply for a third layer. use nailbase on bottom, SA base in middle and cap. Don’t forget your edge metal. Go to or and review their installation instructions for the SA mod bit products. LOL lefty


Finish this job and you could be a manager at Home Depot.[/quote]

lmao priceless!!!

If you find yourself asking advice from a worker at a big box store you may have bit on more than you can chew.

With a bad economy in my area I have found more and more washed up “jack of all trade” types getting jobs for $12-14 an hour at the big box stores. Funny thing is none of them ever carried a license and just did “side work”. Biggest problem is they think they know everything.

You would be better off going on line doing research than asking any questions to workers at the big box stores other than, “What isle are the nails in?”

Gotta think you can get more advice at a small local hardware store.