Backyard Deck, Concrete Patio or Interlock? A Choose-X-If Guide for Ontario

Choose a deck when your back door sits well above the ground or the yard slopes. Choose a concrete patio for a flat, solid surface with little fuss. Choose interlock for a flat surface you can repair in sections. In a deck vs concrete patio decision, grade, drainage and upkeep matter more than looks.

Deck vs concrete patio vs interlock: the short answer

Start with the ground, not the style. Most of the right answer comes from how high your door is above the yard and how water moves across it.

• Choose a deck if the door threshold is more than a step above the ground, the yard slopes away from the house, or you want a raised platform that levels out uneven ground.
• Choose a concrete patio if the yard is fairly flat, you want one solid surface for a barbecue, a hot tub pad or large furniture, and you are happy with a plain or finished slab.
• Choose interlock if the yard is flat, you want a colour and pattern choice, and you like that a sunken section can be lifted and relaid rather than broken out.

A deck is built up from the ground. A patio is built on it. That one difference drives almost everything else in this post: drainage, frost, upkeep and the permit conversation.

Deck vs patio vs interlock side by side

This table compares the three in an Ontario yard. It describes how each one behaves, not a ranking.

No column wins every row. A deck needs framing and footings, but frost does not lift it when the footings are deep enough. A slab is simple but cannot flex. Interlock flexes but needs a good base and regular small attention.

Grade, door height and drainage decide it first

Measure the door. A deck can sit flush with a raised door. A concrete or interlock patio needs a surface that stays below the threshold and slopes gently away from the house. If the ground by your door is already high, forcing a patio there can push water toward the wall.

Look at where water goes. Roof water, snow melt and spring runoff all arrive at the back of the house. A patio is a large hard surface, so its slope has to carry that water to a safe place. Point downspouts away as well, because a downspout emptying onto a patio will freeze into ice in winter.

Permeable pavers are one way to handle water: it soaks through the joints into an open-graded base. A deck handles water by letting it fall between the boards, so the space underneath must stay clear and the ground below should not slope toward the house.

Think about height. Once a deck surface is more than 600 mm (about 24 inches) above the ground, the Ontario Building Code requires guards. Guards are at least 900 mm (about 36 inches) high, or 1070 mm (about 42 inches) when the deck is more than 1.8 m above the ground. Railings add to the cost and change the feel of the space, so a low deck and a patio may look more similar than a tall deck does.

The composite vs wood decking comparison helps once you have settled on a deck.

Frost heave and freeze-thaw: how each one behaves

Frost depth in this region is typically about 1.2 m (4 feet). Water in the ground freezes, expands and lifts whatever sits on it. Each choice deals with that differently.

Deck. Footings go below the frost line, so the frame is not pushed around by freezing soil. Helical piles are an alternative to poured footings. Where a deck attaches to the house, a flashed ledger board keeps water out of the wall. The weak spots are the frame and ledger, not frost heave.

Concrete patio. A slab sits on a compacted granular base rather than footings. Exterior concrete exposed to freezing and de-icing salt is air-entrained, and 32 MPa is a common strength for this exposure. Control joints guide where cracking will occur. Salt is the enemy: avoid de-icing salt on new concrete through its first winter. Cracked or heaved slabs are often removed and re-poured, with the cause (base, drainage, salt) fixed first.

Interlock patio. Pavers move a little with the ground, which is both the benefit and the risk. The base is excavated and built in compacted layers, then topped with a bedding layer, edge restraint and polymeric sand in the joints. Common problems are sunken or heaved pavers, weeds and ant hills in the joints, and edges that spread. Many of these are fixed by lifting and relaying the pavers on a corrected base.

So the question is not which survives winter, but which kind of repair you would rather face: re-pour, relay or re-board.

Upkeep, snow and everyday use

Think about a normal January and a normal July.

• Snow. A concrete or interlock patio is easy to shovel, though salt can damage new concrete and wash sand out of paver joints. A deck needs gentler tools: a plastic shovel used along the boards, not across them.
• Summer. Dark composite boards can get hot on bare feet in direct sun. A concrete slab warms up in the sun too. Interlock holds heat as well, but colour and shade help.
• Cleaning. Composite needs regular cleaning. Pressure-treated wood needs staining or sealing on a schedule. Concrete needs sweeping and, if you choose, a sealer. Interlock needs sweeping, weeding and the odd top-up of joint sand.
• Heavy items. Hot tubs and large planters put steady load on a surface. Ask the installer what base or framing the item needs before you choose.
• Entertaining. A deck feels like an extension of the kitchen when the door is high. A patio spreads out and can reach further into the yard.

A pressure-treated deck needs the most routine upkeep. Composite costs more up front and needs less. Concrete and interlock sit lowest to the ground and need the least routine care, but each has its own repair pattern.

If winter use matters, read deck staining and sealing before choosing wood.

Composite deck vs concrete patio cost: what sets the price

There is no honest one-line answer, because the three options are priced on different things. Comparing them means comparing written estimates for the same space.

• Deck. Height above the ground, size, footings or piles, framing, decking material, railings, stairs and any gates or privacy screens. Composite costs more up front than pressure-treated wood.
• Concrete patio. Excavation and base depth, thickness and reinforcing, forming and access for the truck, finish (broom, exposed aggregate or stamped) and drainage slope.
• Interlock patio. Excavation, base depth, the type of paver or stone, laying pattern, cuts and curves, edge restraint and sand.

On a flat yard with an at-grade door, a patio often involves less structure than a high deck. On a slope or a high door, the deck may be the simpler way to build a level surface. The details of your yard change the answer, which is why a site visit matters.

Use the deck building cost guide to see what a deck quote covers, and ask for the same scope on each option you compare. Do not compare an unfinished slab with a railed deck as if they were the same product.

Permits and zoning: check before you dig

Rules vary by municipality, so confirm with yours. The City of Waterloo says a deck needs a permit if it is more than 2 feet (24 inches) above the ground or has a roof or cover. The City of Guelph says a permit is needed where any part of the walking surface is 24 inches (0.6 m) or higher above finished grade, and it lists concrete porches of any height. Both note that zoning rules on setbacks still apply. Neither page deals with patios directly.

So for a ground-level concrete or interlock patio, ask your building and zoning department about setbacks, lot coverage and drainage before work starts. Also make sure underground utilities are located before digging. Ontario One Call is a free locate service.

If you want the same crew to quote more than one option, D&D Exterior Finishing builds decks, and also handles interlock and concrete work. The free written estimate lists scope, materials, colours and warranty terms, and notes whether a deck permit is likely needed.

Deck and patio questions homeowners ask

Is a deck or a patio better for a sloped yard?

A deck usually suits a slope or a high door, because it is built up from footings and levels the surface without cutting the ground. A patio needs flat, well-drained ground and a gentle fall away from the house. On a steep lot, grading for a patio can be a bigger job than framing a deck.

Is interlock better than a concrete patio?

Neither is better in every yard. Interlock can be lifted and relaid when a section sinks, and it offers more patterns and colours. Concrete is one continuous surface that suits heavy loads, but a cracked or heaved slab is usually removed and re-poured. Base quality matters most for both.

What is the difference between a deck, a porch and a patio?

A deck is a raised platform of wood or composite on footings and a frame. A porch is usually at an entrance, often with a roof and sometimes enclosed. A patio is a ground-level surface of concrete, pavers or stone built on a compacted base. Permit rules treat them differently.

Is a composite deck cheaper than a concrete patio?

It depends on your yard. A high or complex deck with railings and stairs involves more structure. A patio on level ground involves excavation, base and drainage. Composite costs more than pressure-treated wood up front. Ask for written estimates with the same size and scope to compare fairly.

Do I need a permit for a patio in Ontario?

Municipal building and zoning departments set the rules, and the pages for Waterloo and Guelph focus on decks 24 inches or higher above the ground. For a ground-level patio, contact your municipality about zoning, setbacks and drainage before you start, and have utilities located before any digging.

Devon Moore, Operations Lead Co-Founder & Operations Lead — D&D Exterior Finishing

Devon Moore is the co-founder and Operations Lead at D&D Exterior Finishing, specializing in siding, roofing, windows, and exterior renovations across Waterloo Region.