Unheated Building with Slab-on-Grade

[JAE]

Just taking a poll of everyone on what to do for a swimming pool bathhouse. This is a stand-alone building with masonry load-bearing walls on conventional footings and an interior slab-on-grade.

The issue is that in the winter, the building is not used and is open to the weather - unheated. It has a roof over everything, but no insulation.

We are concerned that the slab-on-grade will possibly heave and have wrestled with using a flowable fill under the slab for some depth, or using a uniformly graded granular fill for some depth to minimize heave.

Is this a valid concern and what options could be used?

 

[miecz]

Seems like it would be least expensive to eliminate the gaps so the cold air can't get in. I own a detached (across the street) two car garage in northern Connecticut, where we regularly see temperatures below zero. Our low this year was -7F. This wood frame is uninsulated and sits on a stonemasonry foundation, built in the 1930s. It has a few visible gaps between the foundation and the sole plate. I believe the soil below is clay. On winter nights, the temperature inside is typically 10 to 15 degrees higher than outside. The colder it gets, the greater the difference. Eight years ago I had a contractor pour a 5 inch slab on 10 inches of CGF. To this day, no cracks, no apparent movement. If you can't close your building up, I think you need to protect it to the full frost depth.

 

[jhall]

I have used the Design Guide For Frost-Protected Shallow Foundations to design foundations for unheated pre-engineered buildings. Has anyone else used this design guide?

 

[haynewp]

That guide is one of the links I posted above.
I would like to see what this one has to say

http://www.toolbase.org/tertiaryT.asp?DocumentID=3845&CategoryID=1844

 

[teero]

I would use either insulation or specify free draining material to the frost depth. Insulation rule of thumb, 1"=1' of grade cover. Ofcourse depending on the R value of the material. If you use gran. material make sure there is a weeping tile at the bottom to get any water away.

 

[dazataz]

Similar situation...differnt details:
I am starting a project in Coastal Maine (Hancock)in July. The soil is silt-clay-sand and is high (1/4 mi off coast, 72 ft elevation) with ledge rock all around. Ground water at 20".
We are doing a full 8' basement with walkout and 5-7 feet of backfill, full perimeter drains in & out to a daylight discharge on slope (covered with rock and hay to mitigate freezing), floating slab, 2 Piers for center columns (slab floats around lally columns. I've asked the contractor his opinion and from experience he stated that yes, slabs can lift, and that he can't guarantee anything. We decided adding 4-6" of stone under the slab will allow room for water to flow and/or provide some room to freeze. We'll also provide construction joints or score the slab into quarters.
Here's the beef. The residence will be weathertight by winter, but will NOT be insulated or heated. I'm told the soil generally stays @ 40 degrees F but have decided not to apply exterior insulation to the Foundation to allow the heat from ground to "warm" the unheated space thru the winter. Outside air temps can go below 0 but average 10-30 as lows.
Is this a cause for concern to heave the first winter? In subsequent winters, the house will be insulated, but still unoccupied. Perhaps a supplement of (2)100 watt bulbs will do the trick in the future, but what about the first winter?