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Pad Placement

Written for Canada. Plans are metric, but many crews and suppliers work in feet and inches, so this site gives both: millimetres and metres, with feet and inches beside them. Codes are the National Building Code of Canada 2020 (NBC 2020) Part 9 as your province adopts it. A number marked Confirm has not been checked against every province, so check it with your own authority before you act on it.

Reviewed by a working tradesman with 17+ years in the field.

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Pads carry equipment such as heat pumps, generators and pumps. They have to be flat, solid and strong at the edges.

I am a:

Tap your level and the boxes below open to the advice for you. Remembered on this device.

What it isA small concrete pad that carries equipment such as a heat pump, generator or pump.
Your jobMake it flat, solid and strong at the edges, to the equipment maker's instructions.
The hard ruleThe maker's instructions set the size, thickness and anchors. Get them before you form.
The checkLevel within the maker's tolerance, anchors in place, cured before the equipment goes on.

By the end you can

  • Find the pad size, thickness and level the equipment maker requires.
  • Place and finish a small pad flat with tight edges.
  • Set anchors or sleeves to the maker's layout.
  • Know when the equipment can go on the pad.
Stop and read

Stay away from power, gas and refrigerant lines, and leave all hookups to licensed trades. Call before you dig for the base, because small pads sit close to buried services. Wet concrete burns skin, so wear gloves, long sleeves, tall waterproof boots and eye protection, and use kneeboards or knee pads.

The big idea

Pads carry equipment such as heat pumps, generators and pumps. They have to be flat, solid and strong at the edges, because a pad that rocks or cracks shortens the life of what sits on it.

Pads are ordered and tested to CSA A23.1 and A23.2, but the code does not set a pad size or thickness. The equipment maker's instructions do, and some are part of the permit, so keep them on site.

What the maker asks for

Get the installation manual before you form. As an example of what a maker can ask, one generator maker's support page gives:

  • A concrete pad about 5 in (127 mm) thick.
  • A pad at least 3 in (75 mm) larger than the generator footprint. Its sheet lists 51 in × 28 in (1,295 mm × 711 mm) for a 48 in × 25 in (1,219 mm × 635 mm) unit.
  • The generator level within 0.5 in (13 mm).
  • Anchoring with 3/8 in (M10) lag bolts, with embedment depth set by the local inspector if the code requires anchoring.

For heat pumps, a general HVAC article says most residential pads are four to six inches (100 to 150 mm) thick, slightly larger than the unit base, on a compacted gravel layer, with rebar or mesh at mid-depth if the maker or code calls for it. It also suggests about 1/8 in per foot (about 10 mm per metre) of fall away from the unit. That is general advice, not a maker's requirement, and a maker may ask for a level pad. The manual for your unit decides.

Example quantity. A pad 1.3 m × 0.8 m (4 ft 3 in × 2 ft 7 in) at 127 mm (5 in) is 1.3 × 0.8 × 0.127 = 0.13 m³ (0.17 yd³). The sizes are made up. Ask your supplier about small loads.

Before you pour

Run the checklist on the Concrete Delivery & Preparation page, plus these pad checks.

  • The base is compacted and level, and the pad thickness and edge height match the maker's instructions.
  • Steel or mesh is on chairs, and forms are level and tight.
  • Anchor locations or sleeves are in place, set from the maker's template.
  • Services are located and the pad clears them.
Mix

The code names garage and carport floors and exterior steps (32 MPa with 5 to 8 percent air) but not equipment pads (Part 9, 9.3.1.6). A pad outdoors sees the same frost and wet. Ask your supplier for an exterior flatwork mix, with the exposure class, and use the maker's number if it asks for more.

Placing and finishing

  • Fill edges and corners first, then the middle.
  • Use rakes to pull concrete and do not disturb the steel.
  • Rod small pads, and use a small vibrator on thick ones.
  • Screed to the level the maker asks for. Check across the pad with a long level before the concrete stiffens.
  • Float to close the surface. Trowel after the bleed water is gone, if a smooth finish is specified. See Slab Placement for the finishing sequence.
  • Round the edges with an edger so they do not chip.

Curing and loading

  • Cure with compound or a cover. Below 5°C (41°F), Part 9 requires the concrete to be kept at 10°C (50°F) or warmer for 72 hours after placing (9.3.1.9).
  • Do not set equipment on the pad until it has the strength the equipment maker or engineer asks for. A trade article says on-site pads take several days to harden, and pre-cast pads up to a week. Follow the maker's instruction.
  • Anchor the unit to the maker's template.

Common mistakes

  • Pad not level
  • Steel on the ground
  • Finishing too early
  • Weak edges
  • Not enough curing
  • Loading before strength
  • Forming without the maker's instructions
Pro note

Set a long level across the pad before the concrete stiffens. Dead flat now saves shimming forever.

Weather note

Hot weather dries the surface fast. Cold delays the set. Plan finishing around the conditions.

What the inspector looks at

Base, thickness, steel and level. Some equipment makers' instructions are part of the permit, so keep them on site.

✅ Check yourselfTap a question
A maker says its generator pad should be about 5 in thick. How many millimetres is that, and how much concrete is a 1.3 m × 0.8 m pad (4 ft 3 in × 2 ft 7 in)?
5 in = 127 mm. 1.3 × 0.8 × 0.127 = 0.13 m³ (0.17 yd³). The sizes are an example. Use the maker's manual for the real ones.
The maker says the unit must be level within 0.5 in. How many millimetres is that?
0.5 in = 12.7 mm, about 13 mm. Check the pad with a long level before the concrete stiffens.
Where does the weight of the equipment go if the base under the pad is soft?
The pad settles, tilts or cracks. Compact the base, and call the maker or engineer if the equipment needs a deeper or reinforced pad.
Why round the pad edges with an edger?
Sharp edges chip. A rounded edge holds up.
When can the equipment go on the pad?
When the pad has the strength the equipment maker or the engineer asks for. A trade article says on-site pads take several days to harden properly. Follow the maker's instruction.
May you connect the gas, electrical or refrigerant lines because you are already there?
No. Those are licensed trades. Your job ends at the pad and the anchors, unless you hold the licence.
🧰 Gear for this stepMust-haveRent itNice to have
  • Must-haveLayout and checking:
  • Must-havePlacing by hand:
  • Must-haveConsolidating a small pad: a rod
  • Rent itConsolidating a thicker pad: a hand vibrator
  • Must-haveFinishing:
  • Must-haveConsumables:
  • Must-havePPE:
👷 Who can do thisTap your level
Home DIY
A capable owner can form and pour a small pad for a heat pump or generator on a compacted base. Electrical, gas and refrigerant hookups are licensed trades, and a pad that supports structure or heavy equipment needs the maker's or an engineer's design.
Laborer or helper
Help dig, compact and form the small pad under direction. Stay away from power, gas and refrigerant lines and leave hookups alone. Those are licensed trades. Report a soft or wet base to your lead.
1st-year apprentice
You can form, place and finish a small pad under supervision. Learn to get the pad flat and the edges tight.
Apprentice, 2nd to 4th year
Form, place and finish a small pad and set anchors to the maker's layout, under a journeyperson. Get the pad flat and the edges tight. Make no electrical, gas or refrigerant connections. Ask first if the equipment instructions are unclear.
Journeyperson
You own level, edge quality, curing and the anchor layout. Stop-work triggers: a base too soft or too thin for the equipment, frost exposure the pad is not designed for, or equipment needing a deeper or reinforced pad (ask the maker or engineer).
Lead hand or foreman
Get the equipment maker's instructions before forming and check base, size and anchor layout against them. Enforce the stop-work triggers. Call the maker or engineer if the equipment needs a deeper or reinforced pad. Coordinate pour timing with the licensed trade.
Contractor or business owner
Price the pad as part of the equipment install, and coordinate with the licensed trade. Keep the equipment maker's instructions with the permit file. Ask the maker and your insurer whether a cracked or tilted pad affects the warranty.
Starting a new business
Treat the pad as part of the equipment install and agree scope with the licensed trade in writing. Keep the maker's instructions in the permit file. Confirm permit needs with your building department, and ask your insurer about coverage for a cracked or tilted pad.
By Province:

The technique is the same across Canada. What changes is the code edition and local permit rules. NBC Part 9, Section 9.3.1 gives 28-day minimums of 15 MPa for footings and walls, 20 MPa for floors and 32 MPa for garage and carport floors and exterior steps. Provinces adopt the code with changes, so check your edition. I did not re-verify provincial code editions on this pass, so confirm yours with the local authority.

See Canada by Province for the full comparison.

Sources:

Last reviewed October 2026. General information, not engineering or legal advice.

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