The patio is stained, but still there. Covering it feels less wasteful than breaking it out. Sometimes it is. First, measure the thing that cannot conveniently move: the door threshold.
Draw the layers in section
Put the existing concrete, proposed supports, decking, door sill, and adjacent grade on one drawing. A plan view hides the height problem beautifully. The section brings it back.
Ask how the overlay will stay supported if the existing slab is cracked or moves. An old patio should not quietly become a structural foundation just because it occupies the right rectangle.
Oakville's deck requirements remain relevant when a new deck sits over an old surface. Describe the complete assembly to the building department rather than asking only whether new boards need a permit.
Follow the water under the boards
Where will rain leave the slab? Can debris be cleared from that route? How will the selected decking receive the clearance and airflow its manufacturer requires? Have the installer identify the current product detail, including fasteners, support spacing, and any sleeper conditions.
Do not borrow dimensions from another brand or from a deck raised well above soil. Low clearance is precisely why the detail deserves attention.
Compare the complete alternatives
- An overlay with verified height, support, drainage, and maintenance access.
- Repairing or resurfacing the existing patio where appropriate.
- Removing the slab and rebuilding the outdoor space properly.
Get each option priced to the same finished boundaries. A cheap overlay with an unresolved doorway is not a complete alternative. It is the beginning of another conversation.