Winter frost and heaving patios

Introduction

If you live in northern climates of Canada  such as Nova Scotia you have experienced ground frost.  Why is this bad for pavers, slate and flagstone?  As the soil freezes it expands, this causes a "heave" in the earth.  If the earth heaves and your patio is on top of it, well guess what?  The patio heaves too.  Here we discuss a few ways to prevent that.


Water Retention and dispersion

Soils and substrates that hold water will freeze and heave, a few best practices to prevent that will be:

  • Remove organic layer.  If there is topsoil, roots, composting leaves or moss it must be removed down to a firm insitu material that can bear your patio.
  • Create dispersion if runoff is a problem.  If water cannot get under your shed or patio then the risk of freezing under the shed or patio is greatly minimized.  By creating proper slopes away from the new patio and some ditching divert overland water.
 What causes interlock to settle and shift over time?

Sub Base

Having the proper sub base will greatly improve the performance of your patio and lead to a flatter patio for a longer lifespan.  The sub base typically consists of:

  • Structural fill to bring up the grade to a level sound surface.  This can be existing material if it is firm and sound.  Otherwise if grade needs to be brought up more than 12" it is recommended to use a heavier aggregate such as a 6" minus surge.  Kynocks carrier the following size gradations: 6" minus (Surge), 2" minus (Type 2), 1" Minus (Type 1)
  • Subgrade on top of the surge will need to be a substrate that will compact.  For this we will require a product with fines that can be fine graded (graded with accuracy).  Recommended for this would be a 1" minus, other names or materials similar would be Type 1, Class B, Class A, 1" Crusher Run.
  • Fine grade - on sop of your subgrade to achieve laser accuracy we need a product that is very fine but resist breaking down and washing away.  The ideal product for this is crusher dust.  Crusher dust will be for fine tuning anything less than an inch.


Conclusion

Having the proper subgrades will not only help you resist frost and heaving in our Canadian climate it will mean that your patio will stay looking new for a longer time!  Check out our service areas for delvery then call or click to order!