Should I use a Type S or Type M mortar for paver edge in Ottawa?

For paver edging in Ottawa, neither Type S nor Type M mortar is the correct choice. Standard masonry mortars are not designed for the flexible movement that interlock paver systems require, and they will crack and fail under Ottawa's extreme freeze-thaw conditions.

Proper paver edging in Ottawa requires mechanical restraint systems, not mortar. The correct approach is to install concrete or plastic edge restraints that hold the pavers in place while allowing the natural expansion and contraction that occurs through Ottawa's 60+ degree temperature swings from winter to summer. Concrete edge restraints (precast or poured-in-place) are secured with rebar pins driven into the compacted base. Plastic edge restraints use heavy-duty spikes anchored into the base material.

Why mortar fails for paver edging in Ottawa: Interlock paver systems are designed to be flexible — individual pavers move slightly as the base expands and contracts with moisture and temperature changes. This movement is normal and necessary. Mortar creates a rigid connection that fights against this natural movement. When Ottawa's freeze-thaw cycles cause the base to shift, mortared edges crack and break away, leaving loose pavers that shift under traffic and snowplow loads.

The proper Ottawa paver edge installation process involves excavating a concrete edge beam trench 150-200mm wide and extending to the same depth as the paver base (typically 450-600mm total depth in Ottawa). Pour a concrete edge beam using 30 MPa air-entrained concrete, or install precast concrete edge restraints. The edge restraint sits at the same height as the bottom of the pavers, not the top — it restrains the base layer, and the pavers butt against it. Backfill against the outside of the edge restraint for additional support.

For repairs to existing mortared edges that have failed, remove all loose mortar and damaged material, then install proper mechanical edge restraints. Trying to re-mortar failed edges will result in the same failure pattern within 1-2 freeze-thaw seasons.

Need help finding a paving contractor experienced with proper interlock installation? Ottawa Driveways can match you with professionals who understand Ottawa's climate requirements and use appropriate edge restraint systems for long-term durability.