Tag Archives: gravel pad

Pier Insulation, Hold Up Distances, and Site Prep

This week the Pole Barn Guru answers reader questions about insulating around outside of post piers, the hold-up distance of any non-treated lumber or wall sheathing, and if laying gravel prior to drilling and setting columns would be best order of building.

DEAR POLE BARN GURU: Kind of a 2 parter. I am trenching 4′ straight down around the perimeter (in between posts, just inside the splash plank) of my post frame home. Should I also do the porch on the front of the house? Also I was told I should insulate around the outside of the post piers as well to prevent frost heave. Is this necessary? If so how would I do that if my collard are already poured? DYLAN in GLENWOOD

DEAR DYLAN: Your easiest design solution is to place rigid insulation boards down 2′, then out horizontally (most Building Departments accept 2′ out). This places all of your insulation above tops of concrete collars. This guide should prove helpful (keep in mind, it is for traditional stick built, but concrete has no magical frost preventive properties, so replace “concrete” with compactable fill): https://www.huduser.gov/publications/pdf/fpsfguide.pdf Your porch is best insulated, not only around perimeter, but also under slab itself.


DEAR POLE BARN GURU: Hey I see you post a lot on the pole building pages. I have a question about vinyl siding on a pole building and how to keep the OSB water proof. Which a traditional pole building you have your metal siding attaching to your skirt board, but with vinyl siding you have OSB nailed to your skirt board and then tyvek then your siding. How do you keep the OSB board from wicking water up from the ground when you back fill on the outside of the building? Is there a proper way to keep that water tight? STEVEN in CENTREVILLE

DEAR STEVEN: By Code – any non-treated lumber or sheathing must be kept at least six inches above grade. When we have OSB or plywood sheathing, or T1-11 siding, we use a 2×10 pressure treated splash plank, so there is still 3-1/4″ of splash plank to nail to when sheathing is held up 6″.


DEAR POLE BARN GURU: Is it ok to put in the gravel leveled and compacted before the builder starts building the post type garage This is what they like, not sure why. Thanks. DAVID in SHEPHERDSVILLE

DEAR DAVID: It is going to be far easier (and less expensive) to properly grade your site and compact fill before your building begins, than trying to do it afterwards. Working equipment around posts and walls is going to be time consuming and can result in structural damage, if not done carefully.

Stilt Post Frame on Permafrost

I have written previously about post frame design involving concrete slabs on grade in areas of permafrost: https://www.hansenpolebuildings.com/2018/04/post-frame-permafrost/. Today we will venture into a land where “stilts” are a design solution.

Permafrost is loosely defined as soil and/or rock remaining frozen for more than two years. Big trees do not guarantee an absence of permafrost; it might just mean permanently frozen ground or ice is down far enough so soils in those spots can support a larger root system. Only way to be certain of what ground contains is to have a soils test drilling done.

With permafrost, a safe bet is to it avoid it altogether and move to another piece of land. This is easier said than done, particularly because of a scarcity of affordable buildable land. If you decide to build on permafrost, be as strategic as possible. Smaller and simpler structures will tend to fare better than larger, more complicated ones.

Minimal site disturbance is an accepted practice. Trees and ground cover are your best friend. They protect and insulate ground from summer’s heat. A great example is green moss you find on many shaded low-level areas. Moss has a high insulating value, and in many cases if you dig down a couple of feet, ground might still be frozen in middle of summer.

Strategies for construction on permafrost include:

  • As a general rule, organic layer of ground cover provides insulation and should not be removed, as this will increase risks of thawing any frozen ground underneath.
  • Elevate and properly insulate bottom of your post frame building to prevent floor system heat losses from reaching ground underneath, leading to thawing.
  • Use a thick gravel pad significantly wider than post frame building itself (also insulated if possible) to stabilize the ground and spread building loads.
  • Embed columns to a depth able to both support the structure and resist frost jacking from seasonal ground movement.
  • Cut trees sparingly to maximize site shading (while permitting for a fire break).
  • Build a wrap-around porch, which will help shade the ground around and underneath your post frame building.
  • Incorporate large roof overhangs to shed water away from building and provide shade.
  • Install gutters and manage site drainage well away from building.
  • Retain a geotechnical engineer familiar with local soil’s conditions to assist in designing a foundation system adequate to safely support your post frame building on soils specific to your site.
  • Septic systems also must be engineered to function on permafrost, and remember conventional systems might risk thawing the ground.    

More information on permafrost is available at these websites:

If you have a question, contact the Cold Climate Housing Research Center at info@cchrc.org or 1(907)457-3454.