Can Fiberglass Rebar Be Used in Footings and Foundations?

Fiberglass (GFRP) rebar can be used in footings and foundations, but only as part of a design made for it, not as a substitute for steel bar on a drawing or code detail. The 2024 Ontario Building Code's prescriptive Part 9 rules that call for rebar in foundations assume steel bar, and the code doesn't reference the FRP standards. So a GFRP footing or foundation wall is normally designed by an engineer to CSA S806, using bar made to CSA S807, and accepted by the building department as an alternative solution.

That makes GFRP practical in some foundations and pointless in others. This guide looks at where it fits below grade. For the standards themselves, see does fiberglass rebar meet code.

What the Ontario code says about reinforcement in foundations

Start with what the code actually requires below grade in houses and small buildings:

• Plain footings. Subsection 9.15.3. sizes strip and column footings by width, area and thickness, with no rebar requirement. Our guide to whether footings need rebar covers this in detail.
• Flat ICF foundation walls. Article 9.15.4.5. sets horizontal and vertical bar sizes and spacing, and Sentence 9.3.1.1.(4) requires that reinforcing to conform to CSA G30.18, with a minimum specified yield strength of 400 MPa. That's steel bar.
• Other reinforced concrete. Sentence 9.3.1.1.(3) sends reinforced concrete to Part 4 design, apart from the ICF walls in Subsection 9.15.4. and the cold room slabs in Section 9.40.

Two consequences follow. Where the code requires steel bar, GFRP can't simply replace it. And where the code doesn't require reinforcement at all, a designer can choose to add GFRP, but it should still be their decision, because GFRP behaves differently from steel in concrete.

Where GFRP makes sense below grade

GFRP's main advantages are that it doesn't corrode, it's non-conductive and non-magnetic, and it's light to handle. Below grade, those benefits matter most where steel would be at real risk:

• Foundations exposed to chlorides. Frost walls and grade beams along driveways, parking areas and walkways that are salted, or foundations near salt water.
• Exposed foundation walls and piers at garages, loading areas or structures where de-icing salt splashes onto the concrete.
• Retaining walls next to salted roads or parking lots, where the wall face takes salt spray every winter.
• Special uses where non-magnetic or non-conductive reinforcement is needed, for example near sensitive equipment.

For a typical house footing buried in soil, corrosion of properly covered steel isn't usually the governing problem, so the case for GFRP is weaker. Concrete cover, as set out in CSA A23.1, is what normally protects steel in that position.

What changes when a footing is designed with GFRP

GFRP is not a stronger steel. It has high tensile strength but is much less stiff and doesn't yield. In a footing or foundation design that means:

• More bar, or a different layout. Lower stiffness means wider cracks and more deflection for the same amount of bar, so GFRP designs are often governed by crack control rather than strength. Our GFRP vs steel rebar comparison covers the numbers.
• No field bending. Every corner bar, L-bar, hook, stirrup and dowel has to be made as a bent shape at the factory and ordered before the pour.
• Different development and lap lengths. The bar-to-concrete bond and anchorage rules for FRP differ from steel, so laps and embedment come from the GFRP design, not from steel charts.
• Code scope gaps. US guidance has limits too: ACI CODE-440.11-22, the US building code for GFRP-reinforced concrete, does not address earthquake-resistant structures or anchoring to concrete. Your engineer works out how the design is justified in Ontario.

None of this rules GFRP out. It means the decision is made at the design stage, not at the supply desk.

Footings, dowels and the wall above

Foundations are rarely just a footing. The bars that tie the footing to the wall, the corners and the steps are where GFRP needs the most planning:

• Dowels from footing to wall. These are usually bent L-shapes set in the footing. In GFRP they're ordered bent, with the leg lengths fixed at the factory, so the wall height, lap and cover have to be settled first.
• Corner and intersection bars. Continuous horizontal reinforcement around corners needs factory-bent corner bars in GFRP.
• Stepped footings. Each step changes bar lengths and shapes. Detail them all on the bar list.
• Mixing materials. Some designs use GFRP in the most exposed elements and steel elsewhere. That's an engineering call, including how the two meet.

If the wall above is an ICF wall, the reinforcing rules change again. Our article on fiberglass rebar in ICF walls covers that case.

Retaining walls and garden walls

"Fiberglass rebar for retaining wall" is a common search, and a wall next to a salted road, driveway or parking area is a reasonable candidate for GFRP. In Ontario, Part 4 of Division B applies to a retaining wall exceeding 1,000 mm in exposed height adjacent to public property, access to a building, or private property to which the public is admitted (Division A, Sentence 1.3.3.2.(2)). Those walls are designed by an engineer, and that engineer decides whether GFRP suits the wall.

Lower garden walls aren't regulated the same way, but they still have to hold back soil and water. A wall that leans or cracks because the bar was swapped without a design is an expensive fix. Ask a designer before changing the reinforcement on any wall that retains soil.

Questions to settle before switching to GFRP

If someone on the project suggests GFRP for the foundation, get answers to these before anything is ordered:

• Why GFRP here? Name the exposure or requirement it solves. If there isn't one, steel is usually the simpler choice for a buried footing.
• Who is designing it? The engineer of record has to design for GFRP, not just approve a substitution on the steel drawings.
• Has the building department accepted it? Get the alternative solution reviewed before the bar is ordered, since bent shapes can't be returned or re-bent.
• Does the rest of the foundation still work? Wall dowels, anchor bolts, embedded plates and any connections to existing concrete all need to be detailed for the chosen reinforcement.
• Is the site crew ready? Handling, cutting, tying and inspection practices differ from steel, and the inspector will check the bar against the GFRP drawings.

Ordering GFRP for a foundation

Once the design is done, a GFRP foundation order needs more upfront detail than steel:

1. Bar standard, grade and durability class as specified on the drawings, with mill certificates or test reports.
2. Bar sizes by nominal area, not just a label like "15M", because GFRP sizes don't always match steel areas.
3. Every bent shape on the bar list: dowels, corner bars, L-bars, hooks and any stirrups.
4. Straight lengths that suit the laps in the design, since cutting on site is limited.
5. Accessories: non-metallic chairs and suitable ties, as the specification requires.
6. Lead time, because bent GFRP shapes are made to order.

Our guide to buying GFRP rebar in Ontario goes through ordering in more depth.

GFRP and steel from one supplier

We supply GFRP rebar alongside steel bar from 10M to 55M, with detailing, bar lists and cut, bent and tagged steel to your drawings. If your foundation design uses GFRP, steel or both, send us your drawings for a take-off and quote, or see our rebar products.