Frost prevention

[fire911]

Last winter the frost caused the ground to expand in front of my shed door so I couldn't open it. My question is:
How can I prepare the ground to prevent this from happening again?

Particulars:
I live in New Hampshire, USA, near the seacoast.
Shed is on blocks with sill approx. 6" above grade.
Doors swing out.
Soil type is unknown, but not sandy or clay.


Thank you for any assistance you can provide.

Stay safe;
paul

 

[gtrainor]

The soils are "Frost Susceptible" soils. The soil has the capability of holding water so when it freezes, the water can't really escape and so expands in place causing a heave or swell. If possible, dig out the soils below the blocks to two to three feet down and a foot beyond the block horizontally (You'll have to support the shed around where the block is positioned). Then place in clean angular gravel (3/4 0r 1&quot. Clean means that has been washed with water to remove the finer material such as silt. Compact this as best you can and place the blocks back in place and lower the shed onto it. Bury the gravel with the soil you took out (this will help insulate the soils). The clean gravel won't hold water and the ice in the gravel can expand in the void space of the clean rock. Now when the next freeze comes the gravel won't expand. Type in Frost Susceptible in google search to learn more.

 

[fire911]

Thanks for your prompt an thorough reply. My little manual snowblowers (age 15 & 17) will appreciate being able to get in the shed this winter to utilize the mechanical one.

stay safe;
paul (fire proection engineer)

 

[gtrainor]

I forgot to mention to encapsulate the clean gravel with a filter screen like material. This will help keep fines from the surrounding soil migrating into the clean gravel. Otherwise you'll be right back where you are now in a few years. Find out what the freeze depth penetration is for your area. Dig below that depth to place the gravel.

 

[PEinc]

Check out this thread. Click on the thread link.

thread507-68846

 

[djeep]

As I understand your problem, the soil in front of your shed is heaving at a greater rate than the soil supporting the shed. Consequently reducing the heave of the shed (following the directions outlined above) while not addressing the door sweep area may not completely remedy the problem.

For frost action to occur three conditions must exist: 1) freezing temperatures 2)frost susceptible soils and 3) water must be present.

Eliminating any one of these conditions will greatly reduce the risk of frost heave.

The problem you are describing is fairly common at the entrance to unheated buildings where snow is routinely plowed, and is particularily common when poor surface drainage exists and the underlying soils are frost susceptable.

Granular soils are not inherently frost susceptable owing to their insignificant proportion of silt size particles. However if poor surface drainage or a high water table exists a "bathtub effect" (void spaces fill with water) can be created,causing an increase in the moisture content of adjacent frost susceptible soils and incresed heaving at the periphery of the excavation. Have you ever noticed a bump-dip-bump effect while driving over service trenches which were cut into frost susceptible soils and backfilled with granular soils?

If you elect to replace the frost susceptible soils, as suggested, be sure that the replacement area encompasses the entire door sweep area. Also the gravel need not necessarily be washed or angular, a clean well graded 0-4" sand and gravel would also be appropriate and would have the advantage of:1)less void space to potentially fill with water, 2)decreasing the depth to which frost penetrates below the fill, again owing to a decrease in voids, and 3)possibly providing filter criteria between the native soils and the fill soils, reducing your dependence on filter fabric to prevent the migration of fines.

Rigid flat lying polystyrene insulation is another possibility (major manufacturers typically provide design charts).

I dont know your logistics,i.e. size of shed interior supports etc.., but if the frost heave is fairly consistent year to year would it be possible to raise the shed a few inches?

Again, look at the surface drainage. The ground surface adjacent to the building should be sloped away from the structure at not less than 2%. If the building has gutters they should not discharge in the vicinity of the entrance door.

Good luck