(Sigh) We added a deck last summer. And it is too small in the area where we would like to install a canvas gazebo. We need one more foot on at least one, if not two sides of the deck, in order to install a gazebo. I want to know if it is possible to install 2x4" brackets to the fascia at the joists to support 2-3 more decking boards on at least one of the two sides. The deck is 12x20', but the entry door bay sticks out into this area giving us only a 9x12' area, and we need at least 10x10'.

Can you supply a drawing of what you have and what you want? No, you can not just scab on some 2x4s to make your deck larger. It would be againist code and dangerous.

The only basic way to add onto a deck is remove the outside band and that's usually what the original joist are hanging. Now one can sister the joist and add some length to that. And re-band the new joist. No this will only work if there there is a post and beam to carry the initial load and then cantilever from there a couple of feet.

The side will need another ledger board and another outside bearing post for that new outside corner.
The other side of that needs bearing on the old corner post .

This is just a generic way. As Bal 1 mentioned pictures are needed to fine tune it.

Just thought I mention there is a lot more work here then you may think

I agree with boat21. A picture would be very helpful.

Chuck