We decided to put a room on our little house. It will be a place for out kids to stay when they visit as well as a "workroom" for my wife's projects & crafts. It's 14' square and just off our "boiler" room on the rear of the house, turned down slab with radiant heat like the rest of the house. To avoid traditional 4' frost walls and footers, I'm doing what is sometimes called FPSF or "frost protected shallow foundation" where you put down 2" of xps insulation extending a few feet out beyond the foundation to prevent the formation of frost under the slab's thickened edges. I'll let the pics talk. Notice the overdig, the painted line is where the room ends and the rest of the space is where the insulation is going to the frost from getting under the wall. I used the foam as part of the form work. The concrete block was just dry stacked and packed full of crushed stone to form the interior form & support the insulation Then 2.5" of iso foam for under the slab. This is used material and should have a "R" value of about 16, very important with in slab radiant Then plastic sheeting, rebar & wire and the radiant tubing, AND crossing my fingers hoping the forms are strong enough. Add concrete It turned out very well and I may have just got this in in time before the weather get's to where concrete work is real tough. The forms held straight and we didn't need to add calcium to the mix. My concrete guy put a good hard smooth finish on it or "burned" it. This will be the finished floor like the other floors in the house. I did strip the forms and I'll backfill it, but I'm not sure what I'll get to for framing this winter as my firewood working has been….. really nothing yet this season. This years wood and then some is already to go.
Very nice, but I'm wondering why 2 loops in such a small room. How deep is the slab, and same question for the perimeter? Wife and I have been talking about doing a small addition off our living room, but haven't pulled the trigger, so I'm being nosy. Love this kind of stuff. Do you plan to open up that window for a door? ETA: looks like you put a nice little slope away from the "foundation" with the foam too. Gooder.
Yes Dave, the window will become the door. I just used 2 "loops" because I have areas in the existing house where the outside perimeter is a little chilly on the toesie's. But I didn't do as thorough a job on the wall insulation either. (was worried that the perimeter loops would steal all the heat out of a longer, single loop) The slab is 5" and the turned down edges are 2', leaving about 20" below grade.
looks good fuelrod ... I am not aware of this type of frost protection.. but I do like the idea of radiant floor.. how do you check for leaks which I am sure you want to do before you pour the concrete
Like Dave said, I looped all the ends together and put 60 psi in it with a gauge and monitor it during the pour. That pex is pretty sough stuff. Google that "frost protected shallow foundation" in image's. It's new to me but it seems that it's not all that new of an idea.
What's really important with the shallow frost free foundation is that the insulation keeps its integrity and not be penetrated.
Interesting project. thanks for posting the pictures. We don't have those considerations here for frost protection.
I got it backfilled and covered with hay & plastic for the winter, or late winter?? I really have been neglecting gettin to the wood pile. I just started my wood boiler today and that will help motivate me to get busy making future btu's. I really hadn't planned on fighting winter on this project (with opening up walls on the house) and my goal was to sneak the foundation in so it will be ready to go with better weather. Don't worry, I'll re post when there is something to show, but for now that will hopefully be posting some progress in the "wood pile"
Back at it. This was when I "unwrapped it" after the winter. The first floor walls We decided to make it 2 floors, expanding the bedroom. I'm using all rough sawn full dimension lumber because I like how "beefy" it is, and it allows me to stuff a lot of insulation it the walls. I'm using poly/iso foam and will end up with 4" in the walls and about 6" in the ceiling if I can work it out matching the existing roof line. The walls should end up with an "R" value of about 41, and I'm not sure on the roof yet. These 6X8 timbers are for the floor. We like the timber - barn look, it will get 3/4" pine ship lap that will be the ceiling, with a 2X6 t&g directly on top of the pine for the floor. That get's painted.
looks real good fuelrod... I like beefy beams.. in my mind too many skimp on structure ... and put in pretty.. dumb way to build a house IMO
Hemlock, lot's of it around here. Got a few or the floor beams in today after finally finding some good 8" fasteners. I'm partial to the new structural screws over old time lag bolts. I've had too many of them break or shear off while installing them. I was worried about them "moving" as they dry. This is the north side and only gets sun until about lunchtime, but being green I wanted them screwed and braced as they are surprisingly "true" right now.
