New shop planning stages - Foundation and flooring?

[Wes Billups]

I received some good news the other day and it appears we will be able to start building a detached shop this spring. I'm getting ready to put together a detailed list of items that I'll be able to give to potential contractors so that any bids will be apples-to-apples.

My first of many questions is about insulating the concrete floor. The shop will have a poured foundation that will then have a concrete slab inside. I know I want a minimum of 2" styrofoam insulation under the slab but am wondering how do I make sure the slab is isolated from the concrete foundation wall? I would imagine there could be quite a bit of thermal transfer through the edge of the slab if we don't isolate it in some manner. I'll keep everyone updated on this but right now I'm working on the quote package and am stumped on this.

I've attached a rough sketch of my ultimate plan.
174484
The bathroom may have to wait but I'm sure I want to build the bumpout during the construction phase. If we can't afford to finish it off now, we'll just use it for storage until we can run the plumbing to our septic system. We'll be sure to rough in the plumbing so we don't have to break up any concrete at a later date.

Thanks,
Wes

P.S. I should have mentioned that I'm pretty set on concrete for the floor. I'd love to do wood but due to resale considerations I don't think this would be a wise decision.

[Art Mulder]

Wes, I'm not a concrete contractor, but I don't think that you isolate your slab from the foundation. Rather, ALSO put 2" of styrofoam around the outside of the foundation. So the entire thermal mass is insulated.

[Jaromir Svoboda]

Put 2" insulation between wall and slab.Cut it at 45* bevel so you wont see it,or you can insulate outside wall.
http://www.radiantcompany.com/details/grade.shtml

[Kevin Stockwell]

Search around the www.buildingscience.com (http://www.buildingscience.com) site--they have information on that. It might be in articles about basements

[NICK BARBOZA]

Wes,
You don't really need 2" insulation to get the thermal break from concrete wall to slab. 1" should be fine with the 45* bevel mentioned above (we typically do this in Maine).

On a cost note: If it is possible to work the bathroom into a back corner of the rectangular footprint of the building i would highly reccommend it. The 'bump-out' will add substantial cost to concrete and framing work. Alot of concrete contractors actually estimate projects based on the number of corners. I am sure there are far more driving factors to size/design than I know, but it is a thought to possibly reduce cost. Now that i think about it...this looks like it may be a connector to existing house; in which case... nevermind.

Good luck!
NWB

[Don Bullock]

Wes, congratulations on the plans for a new shop. That's a very exciting event.

I wish I could help you on the foundation/slab but where I live insulation isn't necessary. I would suggest, however, that you talk with some contractors who do this kind of work before drawing up the plans for a bid. As always in these builds, I suggest that you consult your local building code. My shop/garage project was delayed because my designer was unaware of a "new" local requirement that the foundation needed to be 8" above grade instead of 6". By consulting the current building code and local contractors who are familiar with the code you can avoid problems and delays.

I was wondering about what appear to be windows in your plan. As I looked at your drawing it looks like there windows over the "garage" doors that are part of the attic space. They will add considerably to your cost and won't provide needed daylight to your shop.

The bathroom is a good idea. Eventually I plan to have a sink and toilet in a corner of my shop. Again local code may be important here. In our area if a bathroom is present it is assumed that the space can be used as a living space and the code in much stricter than it is for a garage or shop. You will also need to make sure that adding a bathroom will not require a larger septic system.

[Joe A Faulkner]

Wes, are you considering radiant heating in your slab? I've yet to hear of a person who has gone this route and regretted it. Some who have done it, wish they had it in their houses. I was in a shop the other day about the size of yours and the owner told me he heated that and his house with radiant heat. The shop was very comfortable, and it was in the teens that day. Just something to consider. Looks like you will have a great space. Keep us posted.

[Wes Billups]

Joe, I received some rough quotes and don't think I can justify the radiant heat. Here are the different options all from the same company.

$17,000 Radiant heat and split cooling system
$6,000 All electric
$7,500 Gas furnace with AC

The above quotes don't include running the gas line to the shop which was estimated as an additional $2,600 (100' from shop to gas meter). Please let me know if these are in the ballpark.

I'd love to go radiant but since I need air conditioning as well I just can't justify the difference.

[Wes Billups]

Nick, it's funny you mention the back corner as my wife was asking this same question last night. I'm thinking maybe I could go 26' x 50' and take the back 12' for a bathroom, office, and spray room. I thought the side addition would look better with the house but if we can put the money into some details maybe it would make more sense to keep it to four corners.

Thanks also for the thermal break. You and Jaromir have what I think we'll use for the solution assuming I can have the wall's start at the same level as the foundation walls. If I have to have a 8" stub wall above the floor level I'll still need ideas for insulating. Art's idea would work but would require some sort of exterior treatment to protect the foam.

[Rob Fisher]

If I have to have a 8" stub wall above the floor level I'll still need ideas for insulating. Art's idea would work but would require some sort of exterior treatment to protect the foam.

I do not know building codes in your area, but it is typical to require that the wood part of the building be 6" or 8" above exterior grade. This is typically why you step up into a house.

EIFS is installed over exterior foam insulation, stucco can also be installed over exterior foam. Concrete siding may be able to be installed in that location, although I am not sure if it can go below grade. If you want to get fancy you could also do a brick veneer, although that would be considerably more expensive.

Rob

[Jaromir Svoboda]

$ 17,000 for radiant heating is insane.Mine shop is 26 x 31 and I bought 1,000' of 1/2 pex tubing for $ 300,monifold for $ 300 and 2" insulation $ 140 from Craigslist.
Boiler is about $ 1,000 and panel $ 1,300.Some use regular water heater.I dont have mine running yet,not sure if I go with electric or gas.For cooling I have 25,000 btu thru-wall unit.

[Brodie Brickey]

Joe, I received some rough quotes and don't think I can justify the radiant heat. Here are the different options all from the same company.

$17,000 Radiant heat and split cooling system
$6,000 All electric
$7,500 Gas furnace with AC

The above quotes don't include running the gas line to the shop which was estimated as an additional $2,600 (100' from shop to gas meter). Please let me know if these are in the ballpark.

I'd love to go radiant but since I need air conditioning as well I just can't justify the difference.

I think your Radiant quote is from someone that doesn't do it or they added a zero. I'd recheck those figures from another company. You could also put in the tubing and add the heat source later.

[Joe Jensen]

I was just in my brother's shop in Iowa. He did his own radiant system. Pretty simple. He ran the plastic pipe when he poured the foundation. Bought a pump and control system designed for use with an instantaneous water heater. I think he said the water heater was like $800, and the pump and control system was another $400. Not sure on the pipe but it can't be that expensive.

Super nice to have radiant heating. If I had to heat my shop where it's cold and I were building new, I'd for sure lay the pipe when pouring...joe

[Dave Wagner]

I was thinking the same thing on the radiant floor heating, put the PEX tubing before pouring the slab and have it there if you ever need it, adding a small instant hot water and tank type boiler. There are many online retailers for Pex tubing and small systems. I wish I would have done that before pouring mine.

Here a good site and thread on garage heating just to give you some options...
http://www.garagejournal.com/forum/showthread.php?t=63253&showall=1

[jed piatt]

found a good visual

http://www.hydronicpros.com/hydronicheating/services.php


at the bottom of the page is a good graphic of footing slab and wall. the only thing I would do different is raise the wall up so the framing is not that close to the interior grade. depending on how you want to insulate the exterior, you can come up with a complete cold break.
pex is really easy to work with if you decide to save on labor costs. before you install it, lay it out on graph paper first. figure your runs on the length of tubing available to you. don't leave any joints under the floor & work with your hvac guy.

[Brian Schroeder]

Have you considered ICF (Insulating Concrete Forms) for the walls? Little more expensive than stick walls, but when it comes to insulation there really isn't anything better. Next house and shop we build will be made out of it. Actually helped my father build his addition with it. One person can easily put up the forms, just need to grab some helpers when you pour the walls.

[Matt Neil]

When I was preparing to pour the slab, I put 2" insulation underneath and glued 2" insulation along the interior of the foundation, all the way to the top of the foundation (about 1 foot above poured slab). I figured I'd want not just the thermal break between slab and foundation but also insulation against the concrete. Now I'll cover it up with plywood or some material so my kids don't run out there and pull it off the wall.