We are building a new garage and adding a 8′ x 24′ utility room space one the back. The utility room will sit on the slab of the old garage space. The floor will be pressure treated 2″ X 10″ to get the utility room to same level as house. We want to run water, waste and HVAC through the floor (for laundry equipment and maybe a 1/2 bath) What’s the best way to insulate the floor over the slab to protect the water lines? Also, i guess critters could be an issue? We are in mid-atlantic area.
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Some questions:
How much different are the floor and slab elevations? Where will the water supply, HVAC ducts, vents and plumbing come from/go to? How will you access the space beneath?
If going to create an accessible crawl space, the approach would be different that if you had no access. Is this utility space adjacent to the conditioned house space, or is it detached? What is the structure like adjacent to the garage (crawls space, basement)?
I had similar situation, an addition was on a slab on grade,It was where I wanted to locate the laundry room. It was adjacent to an accessible crawl space. Gas, water and drains (sanitary) were all in the crawl space. Gas, water are fed up the adjacent wall and HVAC supplies are overhead, between floors. Sanitary was cut into the slab and cored into the crawl space.
The slab is about 12" below the finished floor space. Right now, we have one step down into the garage. Basically, the existing doorway into the garage will become the door into the mud/utility room. We'll build up the floor from the existing garage slab to the level of the house floor. The HVAC, water, and electric come from the basement adjacent to the new space. The slab is level with the foundation so it will come thru the rim joist.
The builder wants to run everything between the slab & floor and "insulate the heck out of it". The only thing I'm concerned about is the water as the finished floor will be ceramic tile and it would be a pain to get access for service. Thanks, Jim
Run the water line a little over half way up in the 12" space. Use two layers of 2" blue board foam below, in each joist bay. Insulate the remaining area with unface fiberglass batts. Keep the long runs from the basement away from the old exterior walls, and turn them up in a new chase wall that is also insulated. If you are in a real cold climate, you may also over drill the holes for the water pipe and use ArmorFlex insulation on the pipe (the back stuff you see around air conditioning refrigeration lines). If you are still unsure, use a electric heat trace spiral wrapped around the pipe before the ArmorFlex. Turn on the heat trace at the beginning of your heating season and don't turn it off unt spring thaw.
Don't worry about the DWV pipes. The only time they will have water in them is when the bathroom or laundry is in use. Except for the draps, the rest of the pipe is empty all of the time.
Dave