We just started work on another room addition. This client needs the room to house a hot tub that can be used for therapeutic care. We worked with them to come up with a design that is both simple, to keep costs down, but also serves the purpose well.
The floor system for this room will be concrete. We considered wood framing for the floor system but ruled it out for two reasons. First, the distance from the wood framing to the ground is very small. It is always difficult to construct and maintain a wood structure that is close to the ground. Another reason that pushed us toward a concrete floor was the fact that the client planned to mainly use the room for a hot tub. Hot tubs are very heavy. It is much easier to deal with the weight of a hot tub using a reinforced concrete slab than a wood joist system. In addition, a concrete floor generally withstands moisture better than a wood floor system does.
This site has very limited access. We were able to get our skid steer loader and a small truck into the backyard, but bringing in any large equipment is not possible. We carefully excavated the perimeter of the addition and poured insulated concrete foundation stem walls. We will then add floor reinforcing and pour the concrete floor.