Interlocking base preparation guide for Mississauga and the GTA
This step-by-step how-to walks homeowners and small-business owners through preparing an engineered base for interlocking pavers for patios, walkways, and residential driveways. Follow the ordered workflow and the inspection stop points before you place pavers. Use this guidance to verify a contractor’s scope or to attempt a modest DIY install on firm, well-draining soil. If your site has steep slopes, poor soils, frequent heavy vehicular traffic, or buried utilities, stop and request a professional site visit.
When this guide applies and when to call a pro
This guidance is suitable for small to medium patios and walkways and for property managers preparing for contractor bids. Do not rely on it for structural engineering or permitting decisions. Request a professional assessment for any of the following conditions: slopes steeper than one in six, visibly organic or saturated soils, evidence of underground utilities, anticipated commercial traffic, or where municipal permits may be required. HR Greenroots Landscaping offers on-site consultations and maintenance-minded design for Ontario properties if you prefer a site visit before work begins.
Overview: paver system layers and why the base matters
An interlocking paver system is a layered assembly. From bottom to top the typical layers are compacted subgrade, woven geotextile where required, compacted granular subbase, screeded bedding sand, the pavers, and compacted jointing sand. The visible paver is only part of the system. An engineered base prevents movement, settlement, and frost-related damage and determines whether the surface will remain level and tight for years.
Step 1: site assessment and subgrade preparation
Tasks before you dig
- Mark the project limits and measure the area. Allow an extra 100 to 200 mm around the pattern area for edge restraint and compaction access.
- Call your local utility locator before any excavation. Do not assume no utilities are present.
- Check surface drainage and plan for a minimum fall of 1:100 (1%) away from buildings where possible. Re-route downspouts to avoid saturation of the base area.
Subgrade excavation
Remove topsoil, organic matter, sod, and any unstable fill until you reach firm, non-organic subsoil. If you encounter peat, deep organic layers, or standing water, stop and consult a geotechnical or landscape professional. Hand tools are fine for small areas; use mechanical excavation for larger or deeper work. Confirm elevations and slope before placing aggregate.
Step 2: geotextile, subbase selection and compaction specs
Geotextile placement
Place a woven geotextile fabric on the prepared subgrade where soil separation and drainage control are required. The fabric allows water to drain while preventing fines from migrating into the aggregate. Without this separation the finer soil and coarser base will gradually blend, causing the interlocking surface to sink or shift. Technical installation notes for Ontario installations describe this practice and its benefits.
Granular subbase depth and compaction
Common Ontario practice sets a compacted Granular A subbase of 150 to 200 mm (6 to 8 inches) for foot-traffic-only patios and walkways. For residential driveways the base should be deeper and built using heavier materials and compaction equipment, so verify the contractor's specification for vehicular areas. Place the granular material in uniform lifts and compact each lift thoroughly. A plate compactor sized to the area is appropriate for small patios. Larger driveway projects require heavier compaction equipment and professional oversight.
A well-compacted base will be firm and non-yielding under the compactor and will not visibly settle when walked on. If you cannot achieve a uniform, firm surface after compaction, stop before adding bedding sand and consult a contractor. Reworking the subbase at this stage is far less costly than reconstructing the finished paver surface later.
Step 3: bedding sand, paver selection and edge restraints
Bedding sand and screeding
Screed a nominal 10 to 20 mm layer of clean, coarse concrete sand as the bedding for pavers. The bedding layer must be uniform and should not be used to correct an inadequate base. Use two screed rails and a straightedge to ensure consistent thickness and slope. Avoid fine sand that will wash out of joints.
Paver thickness and selection
Choose paver thickness to match the intended load. A common guideline is 60 mm pavers for pedestrian walkways and 80 mm units for residential driveways. Confirm manufacturer load ratings and frost performance before purchase. Ontario-focused references note these thicknesses as common practice for the indicated uses.
Edge restraint options
Install a rigid edge restraint around the perimeter to retain lateral movement. Options include concrete curbs, cast-in-place concrete banding, or manufactured plastic or metal edge restraints anchored into the compacted base. Without secure edge control the paving field can spread and joints will open over time.
Step 4: compaction, jointing sand, and final quality checks
Compaction sequencing
- After bedding and paver placement, use a vibrating plate compactor with a protective mat or neoprene pad to compact pavers into the bedding sand. Compact in overlapping passes.
- Apply dry jointing sand and sweep it into the joints while continuing compaction. Repeat sand application and compaction until joints are full and locked.
On-site inspection stop points
- Before placing aggregate: confirm subgrade is free of organic material and at the planned elevation and slope.
- After compacting the subbase: the surface should be uniform and non-yielding. If you detect soft spots, do not proceed.
- After final compaction and jointing: check that pavers are level within the intended tolerance and that edge restraint is secure.
If any stop point fails, pause work and either rework the layer or bring in a professional. Fixing a poor base after pavers are installed usually requires full reconstruction.
Ontario freeze-thaw and drainage notes
Mississauga and the GTA experience freeze-thaw cycles that amplify the consequences of poor drainage and inadequate base preparation. Ensure positive drainage away from structures and avoid trapping surface water on the paver plane. A properly drained and structured base reduces frost heave risks. Design simple maintenance-minded features such as clean edge control and predictable downspout discharge so thaw cycles do not concentrate water beneath the paving.
Common mistakes, signs of failure and how to fix them
Frequent installation errors
- Insufficient base depth or poor compaction, leading to settlement.
- No geotextile on poor subsoils, allowing fines to migrate into the base.
- Poor edge restraint, permitting lateral movement and joint failure.
- Using fine sand that washes out of joints and undermines interlock.
Signs your base is failing
- Localized depressions or rocking pavers.
- Open joints or shifting pattern lines.
- Surface pooling after rain indicating lost permeability or poor grading.
Spot repairs can address small depressions by removing affected pavers and reworking the base zone. Widespread or recurrent movement usually means the base must be reconstructed.
Printable one-page checklist and what to ask a contractor
Site and materials checklist
- Project area measured and marked; utilities located.
- Subgrade excavated to firm, non-organic soil.
- Woven geotextile placed where soil separation is required.
- Granular A subbase compacted to 150 to 200 mm for pedestrian areas; deeper for driveways (verify with contractor).
- Base compacted in lifts until uniformly firm and non-yielding.
- Bedding sand screeded to a uniform 10 to 20 mm thickness.
- Paver selection: 60 mm typical for walkways, 80 mm for residential driveways (confirm manufacturer specs).
- Rigid edge restraint installed and anchored into compacted base.
- Jointing sand swept and compacted until joints are full. Final inspection for level and drainage.
Direct contractor questions to verify best practice
- What depth and material will you use for the granular subbase for my intended use?
- Will you place geotextile fabric and why?
- What compaction equipment and method will you use for base lifts and final compaction?
- How will you manage surface drainage and downspout discharge?
- What edge restraint will you install and how will it be anchored?
Ask the contractor to show material samples and to mark the elevation and slope before work begins. You can also review detailed installation notes on the HR Greenroots blog, for example the interlocking paver base preparation article at interlocking paver base preparation.
Frequently asked questions
How thick should the base be for a patio, walkway, and driveway in Mississauga?
For pedestrian patios and walkways, a common recommended compacted Granular A depth is 150 to 200 mm (6 to 8 inches). Residential driveways require a deeper, stronger base and heavier equipment; local Ontario practice commonly increases the structural depth for vehicular use. See Ontario installation references for context.
Do I need woven geotextile under pavers and where should it go?
Woven geotextile is recommended where the existing soil can migrate into the aggregate or when additional separation and improved drainage are desired. Install the fabric on the prepared subgrade before placing the granular subbase to prevent soil-aggregate mixing and to maintain drainage performance.
How can I tell if the Granular A subbase is compacted enough?
A properly compacted subbase will be firm and non-yielding under a plate compactor and will not show visible settlement when walked on. For absolute verification on larger projects, professionals use compaction testing. If you detect soft spots or cannot attain a uniform firm surface, do not proceed with bedding and pavers.
What are the earliest warning signs that my interlock base is failing?
Early signs include isolated depressions, rocking pavers, open or separating joints, and surface pooling after rain. Address small issues early by removing affected pavers and reworking the base; recurrent or extensive movement usually requires base reconstruction.
When should I not attempt DIY base preparation and hire a pro?
Hire a professional if your site has poor soils such as peat or high clay, steep slopes, heavy vehicular loads, drainage complications, or any uncertainty about utility locations or municipal requirements. A contractor can provide engineered recommendations, heavier compaction equipment, and a warranty-backed installation scope appropriate for the intended use.
For additional technical reading on base depths and installation practice in Ontario, consult installation notes such as the Oakshs how-to on strong bases for interlock and regional contractor guidance from Cedarwood Development.
If you want a professional site assessment, HR Greenroots Landscaping offers on-site consultations and coordinated design-build services across Mississauga and the GTA. Request a site visit to verify base design and receive a custom quote at HR Greenroots Landscaping.
