Thatch Underlayment

I have my tiki bar built without roof and ready to lay thatch for the roof.

My question to all is.. Is there a good underlayment to place under neath the tahtch to keep rain and moisture out. Thinking that we would be able to saty outside if it is raining a little bit.

I was thinking a tarp or even a camping tarp that is built a bit better.

Any help/suggestions would be great!

What is the base surface? We did my brother in laws roof like you would a house with plywood covered by tar paper and then the thatch.

I have the roof frame and that's it. No plywood or tar paper.

I just have the thatch laid over the roof frame. Layered enough the thatch will keep almost all the rain out. Being in NJ the winters kill the thatch so when I do replace it next it will be with artificial thatch and I'll put down a plywood base covered with tar paper.

I put down plywood, weatherproof paint, tar paper then shingles before putting on the thatch just to be safe!!!

What I'm thinking for the tiki roof to look as real as possible, but with the change of weather is a pain! This will be my final plan:

1. Lay thatch and attach to the roof framing (so when anyone is under the tiki bar, look up and see the thatch)
2. Lay pressure treated plywood with tar paper to seal
3. Layer thatch for the final covering

I attach a bamboo grid to bamboo uprights. The grids are apprx 18” square. I tie the thatch to the grids with jute- looks great from below. I replace the thatch every couple of years and haven’t had a problem with rain. I usually do my replacing in the fall before the rains arrive. Dried out , brittle thatch leaks like crazy
Cheers