Interlock & Pattern Concrete Sealing in Markham — Your Questions Answered

Interlock, natural stone and pattern concrete are an expensive addition to a property, and in this climate they take a beating — road salt, freeze-and-thaw cycles, and constant vegetation growth in the joints. Seal Tech has been cleaning and sealing hard surfaces across the Greater Toronto Area since 1998, and Markham is a long-standing part of our service area. Here's what people ask us most.

Working in Markham

Do you service Markham?

Yes — Markham is one of our named service areas, alongside Vaughan, Woodbridge, Richmond Hill, Stouffville, Mississauga, Oakville, Pickering, Ajax and Whitby, plus Toronto itself. Our project gallery includes both residential and commercial work carried out in Markham.

Do you handle commercial properties in Markham too?

Yes. Beyond residential driveways and patios we do commercial pattern concrete sealing, gum removal, high-rise and low-rise exterior cleaning, and underground parking garage cleaning. Several of the Markham projects in our gallery are commercial.

Why Seal Interlock and Stone at All?

What actually happens to unsealed interlock?

Left unsealed or poorly finished, interlock is subject to staining, discolouration and fading from UV rays, pool chemicals and acid rain, cracking from freeze-and-thaw cycles, pitting, sand loss from the joints, and general daily wear.

What causes the staining?

More things than most people expect. Dirt, calcium, tree droppings such as berries, rust, bird droppings, paint, oil and transmission and brake fluids, leaf decomposition, BBQ or automotive grease, rubber, sap and gasoline all stain stone. On top of that you get growth — fungus, algae, moss, weeds and insect infestation.

Why does pattern concrete need special attention?

Because when it fails, it fails structurally rather than just cosmetically. Left unsealed and unmaintained, pattern concrete deteriorates prematurely, begins to pit, and eventually breaks up. Resealing roughly every two years is what protects the investment. A new seal also lifts the curb appeal noticeably — enough that real estate agents often recommend it before a property goes on the market.

The Sealing Process

What does the job involve?

• A high-pressure chemical wash, with scrubbing where needed, to remove stains.
• Removal of efflorescence — the whitish chemical powder that appears on interlock and concrete.
• Removal of existing weeds and other vegetation.
• Application of polymeric joint sand, which hardens like a flexible mortar to reduce weed growth, bug infestation and erosion.
• An overlapping coat of sealant in your chosen finish.

What is polymeric joint sand and why does it matter?

It's the sand that goes between the stones, and unlike ordinary sand it sets firm while staying flexible — like a mortar that can move. That's what keeps weeds from pushing through the joints, discourages insects nesting underneath, and stops the joint sand washing out every time it rains.

There's white powder all over my driveway. What is it?

Efflorescence — a whitish chemical powder that surfaces on interlock and concrete as moisture moves through the material. It isn't damage as such, and removing it is a standard part of our cleaning before any sealant is applied.

Can you get rid of the moss and weeds permanently?

We remove the existing growth and then apply polymeric joint sand specifically to reduce it coming back. Nothing outdoors is permanent, but sealed joints with proper sand are a very different proposition from open joints full of loose sand.

Finishes & Maintenance

What finishes can I choose from?

• Clear sealer, natural look — won't change the appearance of your stone. The finished result looks very close to how the stone looks after cleaning and drying.
• Semi-gloss "wet look" — roughly 12–15% acrylic post sealing, giving the stone the appearance it has after light rain, with a little shine.
• High-gloss "wet look" — roughly 20–25% acrylic, for the shiny wet appearance of stone after heavy rain, intensified by the extra acrylic.

Will my driveway be slippery once it's sealed?

We use a slip-resistant final sealer as a standard feature on all pattern concrete and natural stone we seal, specifically to reduce the danger on wet surfaces, and there's a slip-resistant option for smooth non-porous concrete. Any surface can still be slippery when wet or icy.

How often does it need redoing?

Every two to three years is common practice. It depends on sun exposure, moisture, overhanging trees, salt exposure, traffic and how the surface is cleaned.

Can you remove old stains, or is that permanent?

Most rust and other stains can be removed from interlock, concrete and natural stone with our power washing process and a range of cleaners and techniques. Some stains are permanent and can't be removed by any process — we'll tell you which yours is rather than promise a result we can't deliver.

How soon can I drive on it?

Rain safe in about 30 minutes, walk safe in about 4 hours, and vehicle traffic after 24 to 48 hours. Actual times vary with temperature and sun exposure.

More Services

• Interlock Cleaning & Sealing
• Natural Stone & Pattern Concrete
• Commercial Services
• Deck & Fence Staining
• Project Gallery
• General FAQ

Questions we haven't covered? Call (416) 966-4200 and we'll talk it through.