Converting deck to addition?
Due to bid coming back much higher than expected for a 30 foot wide, 12 foot deep bumpout, I am working on scaling back the bumpout area to perhaps just a 10x12 foot breakfast room. Right now we have an 11 foot deep treated pine deck that runs across most of the back of the house, between 10-30 inches off the ground. It is 15 years old but looks in great shape since we have it cleaned and stained every 2 years. In the interest of economy, can this breakfast room be built on the existing deck? The deck now sits about two inches below the floor level. This would allow us to not have to tear out the rest of the deck, which could flank the addition on both sides.
Some considerations I have thought of:
1. Can supports/posts be added if necessary to an existing structure to support an addition?
2. Would it be best to remove the decking in the addition area to add insulation underneath??
3. I think that I could add sleepers on top of the decking with 1.5 inch rigid foam insulation, topped by a plywood subfloor, for additional insulation. Or would it be better to remove the decking entirely in the addition area an create a subfloor on the joists?