How to turn a deck into a room?

Have you first checked to see what permits are needed? There should be basic guidelines or specs you need to follow just to comply with local requirements.

This isn't an inexpensive endeavor. Permits need to be pulled and inspections need to be scheduled. Chances are foundation work will need to be done to carry the additional load. Check with your local Building permit office and follow local code. It is far more involved than slapping up some framing - fire and safety codes need to be followed.

Yep. You need to check what your local building codes are and if it's allowed. Also check with your homeowners insurance. They may not approve and insure.

If this is going to be part of your house, like Mogie said you'll probably need permits. You can't just frame on top of a deck, it will need proper footings and foundation to build a room. Pallet wood isn't strong enough or big enough to build with. You can't just sister the wood together and expect it to be able to support a roof let alone the windows, sheetrock and everything else you're putting in there. Save the scrap wood for furniture if you want to use it. Save your money for the proper materials so that you have a safe home. Don't forget that you'll need electric and hvac run also.

I doubt if using pallet lumber for enclosing a deck would pass inspection, or meet building codes, as it is not a veritable approved interior construction material.

Enclosing a deck is often considered an improvement that adds to the interior sq footage of a home. Not completing the job properly may null your home insurance policy if you were ever to file a damage claim.

No permits needed....here ya go.

https://www.youtube.com/watch?v=0jhqbnM-5XQ

https://www.pinterest.com/pin/475763148105087195/