Ontario's Plain-English Guide to Custom Home Buildingπ 705-533-1633 | βοΈ 1-866-868-6606 | βοΈ info@icfhome.ca
Spray Foam Insulation Cost Calculator Ontario (2026): Board Feet by Surface and Thickness, Closed or Open Cell, Rim Joists, Masking, Backing, Thermal Barrier, Minimum Charge and HST
Insulation & Air SealingFree Calculator
What Should Spray Foam Cost? By the Board Foot, Surface by Surface, With the Thickness That Decides the Price and the Masking Nobody Mentions.
Closed or open cell, each surface at its own thickness, rim joists by the foot, masking, backing, the thermal barrier, the minimum charge, HST. And the R-value each inch actually gives you. No email address required.
Spray foam is sold by the board foot: one square foot, one inch thick. A quote that says “$4,800 to foam the basement” without the thickness is a quote for an unknown amount of foam, and 2 in. and 3 in. on the same wall are 50% apart in money. The other thing that moves a foam quote is everything that is not foam: masking the windows and the furnace, cardboard or OSB backing in open bays so there is something to spray against, the drywall or coating the code wants over foam that stays exposed, and the fact that two men, a truck and a rig do not come out for 400 square feet. This calculator prices all of it the way the sub prices it for me.
Step-by-step
Spray Foam Calculator (Ontario)
1
The surfaces being foamed
| Surface | Area (sq ft) | Thickness (in.) | Foam | Where |
|---|
One line per surface. Basement walls: perimeter x height less windows. A cathedral roof: the slope area. Closed cell is about R-6 per in. (2 in. = R-12, 3 in. = R-18, 3.5 in. = R-20); open cell about R-3.7 per in. and never below grade or against roof sheathing without a vapour retarder.
Perimeter of the house at the floor framing. 2 in. closed cell in the rim, $5.50 per ft. Rim joists.
Closed cell runs $1.00 to $1.50 a board foot and open cell $0.90 to $1.20 with the crews I use. The low end is a big open wall; the high end is a crawlspace on your knees.
2
The work around the foam
Cardboard or OSB in open joist bays, behind a knee wall or at the rim where there is nothing to spray against, $2.00 per sq ft. Zero on a bare concrete wall.
Foam that will not be covered with drywall needs a thermal barrier (OBC 9.10.17): intumescent coating at $1.60 per sq ft. In a crawlspace or attic an ignition barrier at $1.25. Put the drywalled area at 0.
3
Where is the house?
Material costs the same everywhere; labour does not, and insulation is mostly labour, a truck and two men in a crawlspace.
Used only to tell you whether the house is in our direct service area. Not stored.
Enter a postal code to see service coverage.
BuildersOntario.com
Your Spray Foam Budget
Illustrative Ontario estimate
| Item | Estimate |
|---|
Estimated total with HST$0
Example only, using BuildersOntario budgeting rates checked October 2026 for medium-density closed-cell (2 lb) or open-cell (0.5 lb) polyurethane foam sprayed by a CUFCA-certified installer to the stated thickness in passes the product allows, with the daily work sheet, on a clean dry substrate above 5 C, with normal access. It includes the masking, backing and barrier lines you selected. It does not include removing old insulation, framing, drywall, electrical moves, moisture repairs to the foundation, or heating a cold basement so the foam cures. Thickness is what you asked for, not a statement that it meets the code for your assembly; the SB-12 form for the house says what it needs. The contractor’s site measure governs the contract, not this page.
Request a Real Quotation
Your surfaces, thicknesses and board feet become a written scope a spray foam contractor can price without a site visit, so three of them price the same foam. It goes straight to our inbox, and a copy comes back to you; reply to that copy with photos of each surface (the basement wall, the rim, the roof slope), a photo of the furnace and water heater area, and the house plans if you have them.
What this calculator does, and what it will not do!
It prices foam the only honest way, by the board foot, so that 2 in. and 3 in. on the same wall come out as different jobs, and it shows the R-value each thickness gives so you can see whether the thickness on a quote is a number somebody chose or a number the wall needs. It adds the lines that live outside the foam price: masking, backing, the barrier over exposed foam, the minimum charge.
It cannot tell you whether your assembly should be foamed at all. Foam is the right answer at the rim, on a concrete wall, in an unvented roof and in a floor over a garage; it is the expensive answer on an attic floor and in an open stud wall that a batt and good air sealing would do. Where foam wins and where it does not. This is a budget; the contractor’s measure is the quote.
A rule of thumb: in Ontario in 2026, closed-cell foam runs $1.00 to $1.50 a board foot with the crews I use, about $1.25 as a planning number, and open cell $0.90 to $1.20. A 36 by 28 basement at 3 in. (about 2,950 board feet) with the rim joists is $4,400 to $5,000 before HST; 2 in. is about $3,500. Small jobs cost more per foot because of the minimum, not the foam. Nobody comes for less than about $1,200.
How I price it
| Line | Rate | Notes |
|---|---|---|
| Closed cell, 2 lb | $1.25 per board ft | R-6 per in. nominal, R-5.6 aged. Air barrier and vapour retarder at 2 in. $1.00 to $1.50 depending on access and how much there is; quotes up to $2.50 a board foot on small jobs are the minimum charge talking. |
| Open cell, 0.5 lb | $1.05 per board ft | R-3.7 per in. Sound and air sealing in interior walls and vented roofs; not below grade. $0.90 to $1.20. Cheaper per board foot, but it takes about 60% more inches for the same R. |
| Rim joists | $5.50 per linear ft | 2 in. closed cell in a 10 in. rim with the sill and joist ends. The foam is a third of it; the crawling is the rest. |
| Masking | $150 to $500 | Overspray goes everywhere. Windows, furnace, water heater, plumbing, your stored boxes. |
| Backing | $2.00 per sq ft | Cardboard or OSB where there is nothing behind the bay to spray against. Open joists, knee walls, some rims. |
| Thermal barrier | $1.60 per sq ft | Intumescent coating over foam that stays exposed in a living space (OBC 9.10.17); or 1/2 in. drywall at the drywall rate. Ignition barrier in a crawlspace or attic $1.25. |
| Minimum charge | $1,200 | Two men, a truck and a rig. “It is not worth going out for 400 sq ft of wall.” |
Checked against Ontario spray foam crews each month. Spray foam costs has three jobs worked through; closed vs open cell explains the two products.
Where homeowners go wrong
- Comparing quotes without the thickness. “$4,800 for the basement” at 2 in. and “$6,200” at 3 in. is not a $1,400 difference; it is a different wall. Board feet on every quote.
- Open cell below grade. It drinks. Closed cell on concrete, at the rim, in a crawlspace. What goes against concrete.
- Leaving foam exposed. Foam burns and smokes. The code wants a thermal barrier over it in living space; a garage ceiling with bare foam under a bedroom is a fire inspector’s favourite photo. The barrier rule.
- No certification, no work sheet. Off-ratio foam that shrinks, stinks and pulls off the studs is a real thing, and the daily work sheet with lift thickness and density is how you know it did not happen to you. Problems and the checks.
- Foaming the attic floor. Three times the money of air sealing plus cellulose, for the same R. Foam the rim and the slopes; blow the flat.
Questions people ask
How much does spray foam cost per board foot in Ontario?
Closed cell $1.00 to $1.50 a board foot installed in 2026, with $1.25 a fair planning number; open cell $0.90 to $1.20. Small jobs get quoted higher because of the minimum charge, not because the foam costs more. A board foot is one square foot at one inch thick, so 1,000 sq ft at 2 in. is 2,000 board feet, about $2,500 plus masking and HST.
How thick should closed-cell foam be on a basement wall?
About 3.5 in. to reach R-20 on its own, which is what a finished full-height basement wall in Ontario needs. Many jobs do 2 in. (R-12) with a 2×4 wall and R-14 batts in front, which gets there cheaper. Either way the number should be on the quote with the R-value beside it. Basement assemblies priced.
Does spray foam need a vapour barrier?
Closed cell at 2 in. or more is its own vapour retarder and air barrier; no poly. Open cell is not; it needs a vapour retarder on the warm side in our climate. On an ICF wall none of this comes up; the foam is already there. ICF and foam.
Why is there a minimum charge?
Because the foam is cheap and the trip is not. Two installers, a heated truck, a proportioner and a day’s setup cost the contractor the same for 400 square feet as for 4,000. Bundle the small job with the rim joists or a garage ceiling so the trip earns its keep.
Is spray foam safe once it is cured?
Properly mixed and applied, yes, after the re-entry time the product sheet gives (usually 24 hours with ventilation). Foam that still smells after a week was off-ratio or too thick per pass, and that is a warranty conversation with the contractor and the manufacturer, which is why you want the certified installer and the work sheet.
Comparing a foamed wall to a batt wall or ICF?
The Wall Assembly Comparison Calculator prices the same house with batts, exterior foam, flash and batt, full foam and ICF, and shows the effective R-value and the heat going through each. If you already have foam quotes, the $99 quote review puts them on one grid by the board foot.
