30-35K shot in the dark. But you more than likely cannot build that on top of you existing deck. It will be too heavy as decks are not designed for that type of load typically.

Thanks millworkman. But I'm going to get some post and put them into the ground after I cut into the deck.

Measure out the exact size you will build. Put together a list of materials-include everything-screws, concrete, lumber, plywood, sheathing, shingles. This will give you an exact dollar figure . Do you need new tools for this project? Add that cost so you won’t be surprised by another $800-2000. We can’t make this list for you.

Don't forget to check with your local building inspector office to see if you need to pull permits and if so how much the permits cost for you to do demo and building. You might not need permits, but a lot of places do require them so it's wise to check.

The cost of materials is also going to depend on what materials you have planned. If you are using pine vs cedar or a composite material, 10 year vs 30 year shingles, and so on.

A detached pavilion on a raised deck, just go to Costco or Sams and buy a prefab kit for $1700.

Costco I was gonna say...