What about having the piece of XPS tall enough that it laps the foundation by a foot or more, glue it to the foundation.

Your drawing says "#4 @ 32" O.C." Send the rebar through the rigid foam.

Chris

I like the drain to stop some of the radiant flow. I will do that on my next house.

However I was thinking about having a 2x6 vinyl or composite decking board rotated on edge, aligned to the garage door seal. Not great, but a 1" or 5\4" wide board exposed to traffic will hardly take any weight and should act as a thermal break well enough for me.

I see where Lowes now carries EverTru solid PVC moulding in various sizes. One piece I noted was 5/8" thick x 1-1/2" wide x 12' long. You could cut a piece of 1" thick EPS or XPS foam just shy of the top of the concrete by 5/8" then lay this piece of PVC flat wise on top of the foam and secure in place with glue or canned foam prior to pouring the concrete. This would provide a good thermal break while providing protection for the insulating foam below.

http://www.lowes.com/pd_113010-1487-02150_0__?productId=3339300&Ntt=pvc+moulding&pl=1¤tURL=%3FNtt%3Dpvc%2Bmoulding&facetInfo=

We frequently use the drainage grate approach to thermally isolate garage entrances. There is 2" of XPS on each side of channel, so about R21. The drain line is 1" pex and simply drains to exterior of garage (i.e., not attached to storm/waste lines), so there isn't any chance of water backing up. We also get a lot of rain in the PNW, so garage drainage grates are fairly common even for garages without hydronic radiant floor heat...although I can't imagine anyone who spends any time in their garage/shop not being able to dial up a heated floor (or car lift) when desired...

Well I poured the footings today so I would appreciate any last comments on this topic. At the moment I am leaning toward 2" XPS across the inside of the garage wall, rebar tied across to the apron, and possibly tapered at the top to 1"

Sounds like a good plan to me. Wish I had done that in my radiant heated garage.

Chris

rebar tied across to the apron

The rebar is unnecessary if you are properly compacted inside and out, although aren't you in a very mild climate? If that's the case, the heat loss won't matter much for the peace of mind over the settling.

zone 5 Chicago. The apron will sit on the garage foundation so it won't sink. I will be sure to compact the garage. I am thinking it is code here to have the rebar anyway. I guess I will press on with the 2" XPS break across the garage bays

Another question about this. With the rebar across/through the foam, the apron sitting on top of the foundation wall will be a 10"x6" apron block of concrete sitting by itself on the foundation. With the garage door sitting on the foam (sealed well) i am curious if anyone has an opinion if should the seal break, or leak water, water would weep down and under that 10x6 block of apron concrete and freeze, heaving it up, since the foundation wall wont move?

Posted By ICFHybrid on 14 Sep 2013 12:29 AM

How long does expose eps stand up to weather and vehicle traffic?

I have 2" wide XPS in there and after a year and a half, it shows essentially no wear. My garage slab is about 1/4" higher than the driveway slab and the XPS sits about 1/4" below the driveway slab, so it is down in a "slot" which seems to protect it some.

what zone/climate are you in?

Posted By spall on 29 May 2014 06:08 PM
Another question about this. With the rebar across/through the foam, the apron sitting on top of the foundation wall will be a 10"x6" apron block of concrete sitting by itself on the foundation. With the garage door sitting on the foam (sealed well) i am curious if anyone has an opinion if should the seal break, or leak water, water would weep down and under that 10x6 block of apron concrete and freeze, heaving it up, since the foundation wall wont move?

Surf - you have several problems. With no support where the rebar goes through the foam, the rebar has no value. It will bend.

There is no question that the seal will leak and over time, in a big way. A few thermal cycles in your clime will tear the concrete away from the foam. Not only will it cause frost heave but you will be bringing salty water/slush into the garage when you drive in. This will drain through the crack and cause the rebar to rust, causing the concrete to spall.

Well I'm glad I asked the question! Interestingly enough, some guys on the GarageJournal.com site in WI, OH and Ontario have this done and claim to have no issues. Any ideas on how to accomplish radiant garage heat in my garage?

Posted By Surfsup on 30 May 2014 02:51 PM
Well I'm glad I asked the question! Interestingly enough, some guys on the GarageJournal.com site in WI, OH and Ontario have this done and claim to have no issues. Any ideas on how to accomplish radiant garage heat in my garage?

Heres a detail on an ICF wall

Typically, water and salty water end up in the area where the overhead door sits on the garage slab because the slab is typically sloped toward the overhead door and the door tends to dam the water. I would be concerned about this water getting past the composite board, causing the rebar to rust (perhaps resulting in concrete spalling), and perhaps getting under slab/apron area causing frost heave. Much of this water comes from melting snow or water drainage from the vehicles and not so much from outside the overhead door. We have found that having a drainage grate just inboard of the overhead door effectively addresses both this water and the thermal break. Is there something about the effectiveness of composite board dovetails that mitigates my concern in actual practice?

••• Is there something about the effectiveness of composite board dovetails that mitigates my concern in actual practice?•••
The rebar holds the two slabs together and the composite is fairly stable through a large range of temperature and moisture. The dovetails provide enough of a keyway to stop 95% of the water ingress provided the concrete is well consolidated filling the keyway with paste.

I have not as yet had the pleasure of working with a trench drain that has the ability to structurally bond two slabs, so when we use trench drains in a structural or semi structural setting, we detail the rebar under them to make it one slab. This is usually a complex detail as we have to offset the structural strengths around the drain. An of course the concrete under the drain would provide a thermal bypass.

Surf lives in the windy city so I suspect his frost protection is about 36" deep. This means that his foundation is trenched in (unless he is going slab on grade) leaving the area of the drain (or any break) at the weakness area (most susceptible to settlement) so if the rebar is not properly detailed there will be issues. If we can guarantee 96% Proctor, this would not be an issue but we seldom see that kind of compaction in a residential setting.

For a trench drain to work as a thermal break, it needs to have its front lip almost under the door. (and of course it must be of a material other then steel) If the drain is deeper the slab, and most are, it would be in close proximity or in conflict with the foundation wall. 8" foundation, 6" stud wall.

If you find a drain that is not deeper than the slab, we would still need to make sure that it doesn't cause the two slabs to separate. If placed at the door, the apron would have to be secured to the drain in such a fashion to prevent the apron from walking away from it during temperature cycles.

Yes, my garage is excavated, footing will be 48 below after finish grading. I think I am just going to pour a continuous garage slab. I installed foamular250 on the inside walls from the footing up to the top of foundation. I figure this will hold some heat in. I'll trim the F250 @ the doorways so it doesn't span across, only against the concrete,wall so there is no thermal break. With the foam on the walls it will be a bit warmer in the garage. If I do radiant I might only run tubing in the back 2/3 of the garage but that might just be pointless. I'd rather keep the risk low than have the break. I suppose radiant in the basement will have to be enough...

As I said before I didn't do a break across my 2 garage door openings and 1 entry door. Has worked fine for 4 winters.

I keep the garage between 50*- 60*F. The first tube is set back about 15" from the inside of the foundation.

I also have the rigid foam on the inside of the foundation from footing to top of slab, cut to 45*.

Chris

If you are going to insulate the foundation, I always think it is better to put the foam on the outside. Why stop the cold when it is already in the foundation?

Good point, I think it was done that way so it could be used as the slab perimeter insulation. Should probably do both.

ChrisJ in RI

Thought about,both but,didn't do outside...still debating radiant without the break but think it is a waste of heat...waht are your bills for that slab with no break? Also, what climate do,you live in?