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Retrofit Anchors

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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Retrofit anchors tie an old building to its foundation. An engineer designs them. You install them exactly.

I am a:

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

What it isAdding anchors and connections to an existing building so its frame is tied to its foundation.
Your jobTest for hidden hazards, check the concrete, then install exactly what the engineer designed.
The hard ruleDo not design a retrofit from this guide. Stop if the concrete is poor or a hazardous material turns up.
The checkHazard testing, concrete condition, product approval, hole preparation, embedment and cure or torque.

By the end you can

  • Say where retrofit anchors are used and why they need an engineer.
  • Check old concrete before drilling.
  • Name the stop triggers on a retrofit job.
  • Describe the installing steps for epoxy and mechanical anchors.
Stop and read

Old buildings hide hazards: asbestos, lead paint, vermiculite insulation, mould, old wiring and plumbing. Have materials tested by a qualified person and follow your provincial rules before anyone drills or disturbs anything. Crawl spaces are confined spaces (see Sealed Crawl Space).

Drilling concrete makes silica dust. Use dust extraction or water, a respirator suited to the job, and scan for rebar first (see Epoxy Anchors).

Do not design a retrofit from this guide. The right retrofit depends on the building's age, soil, concrete and framing, and older buildings need an engineer.

The big idea

Many older buildings were never bolted to their foundations, or the bolts are missing or in the wrong place. A retrofit anchor ties the frame to the concrete after the fact. A Victoria Heritage Foundation guide calls the short cripple wall between the foundation and the first floor the weakest structural link in a wood-frame house, and says the fix is to connect the house firmly to the foundation and stiffen that wall into a shear wall. It must have all three: foundation bolts, plywood sheathing nailed in a tight pattern, and shear transfer ties to the floor above. Hold-downs go at each end of tall, narrow shear walls.

What the rules say

  • The Victoria Heritage Foundation guide (2025, a BC grant program) says seismic upgrades it funds on heritage foundations, chimneys and roof structures must be designed by a professional structural engineer, and that the 2012 BC code's prescriptive rules for new construction are likely not directly applicable to heritage buildings.
  • For adhesive anchors, design information comes from a product evaluation report, and the maker's printed installation instructions govern cleaning, working time and cure (see Epoxy Anchors for sources).
  • For new work, Part 9 anchorage rules are in Anchor Bolts. They are not a retrofit design.

The guide I read does not cover anchor types, spacing, concrete condition or hazardous materials, so those points below are common practice and the product sheets, not a code citation.

Types of retrofit anchor

  • Epoxy-set threaded rods: for high loads and for concrete that may be cracked, if the product is approved for it.
  • Mechanical (wedge or screw) anchors: for lighter loads in sound, uncracked concrete.
  • Expansion anchors: only in sound concrete and where the product is approved for the use.
  • Retrofit hold-down systems: designed for the job.

Where they are used: old sills that were never bolted down, missing or misplaced bolts, hold-downs on braced walls, garage-to-house connections, and structural corrections.

Check the concrete first

  • Look for cracks, crumbling and honeycombing. Old or damaged concrete may not hold an anchor.
  • Check that the concrete is thick enough and that the anchor has enough edge distance.
  • Locate the rebar before you drill.
  • Ask the engineer if the concrete is in poor condition. Never decide that poor concrete is good enough.

Installing

  1. Drill. Use a rotary hammer with the bit size the anchor maker states.
  2. Clean. Clean the hole as the product requires.
  3. Epoxy. Inject, insert and let it cure as in Epoxy Anchors.
  4. Mechanical. Set to the depth stated and tighten to the torque the maker gives, then check.
  5. Hardware. Fit the plates and nuts as the design says.
  6. Record. Photograph each anchor and keep the product sheet.

Example (numbers made up). Adding 12 anchors at about 20 minutes each for drilling and cleaning is 12 × 20 = 240 minutes, or 4 hours, before any cure time. Plan the cure from the product sheet.

Common mistakes

  • Anchors in cracked or crumbling concrete
  • Poor hole cleaning
  • Wrong embedment
  • Non-approved epoxy
  • Over- or under-tightening mechanical anchors
  • Not checking for hidden hazards
  • Designing the retrofit without an engineer
Pro note

In an old building, expect surprises. Take photos before you start, and call the engineer when the concrete or framing is not what the plans show.

Weather note

Cold slows epoxy cure and wet holes ruin it. Heat shortens working time. Damp old basements may be too wet for some products, so check the maker's limits.

What the inspector looks at

Product approval, hole preparation, embedment and torque or cure, often with an engineer's review before the work is covered. Confirm what your building department requires.

✅ Check yourselfTap a question
According to a Victoria Heritage Foundation guide, which part of an older wood-frame house is the weakest structural link?
The short cripple wall between the foundation and the first floor.
What three things must all be present for a cripple wall retrofit to work, per that guide?
Foundation bolts, plywood sheathing and shear transfer ties. It also says hold-downs are required at each end of shear walls that are tall relative to their width.
Who designs a seismic retrofit for an older or heritage house?
A professional structural engineer. That guide requires it for its grants, and the new-build Part 9 rules are likely not directly applicable to old buildings.
Before you drill into old concrete, what do you check?
Cracks, crumbling and honeycombing, thickness and edge distance, and where the rebar is. Ask the engineer if the concrete is in poor condition.
A basement wall has 12 anchors to add. Each hole takes about 20 minutes to drill and clean. How long is that?
12 × 20 = 240 minutes, or 4 hours. Times are made up, and the cure time comes from the product sheet.
The test shows vermiculite in a crawl space. What do you do?
Stop. Do not disturb it. Have it tested and handled by a qualified person under your provincial rules before anyone drills or enters.
🧰 Gear for this stepMust-haveRent itNice to have
  • Must-haveLayout and scanning:
  • Rent itDrilling (machine): rotary hammer with the bit size the maker states and a dust extractor
  • Must-haveHole cleaning (hand tools):
  • Must-haveAnchors:
  • Must-haveTightening and checking:
  • Must-haveCrawl space and old buildings: coveralls, knee pads, work lights, and test kits for old materials (testing is done by a qualified person)
  • Must-haveRecords:
  • Must-havePPE:
👷 Who can do thisTap your level
Home DIY
Do not design or install structural retrofit anchors yourself. Old concrete, hidden hazards (asbestos, lead, vermiculite, mould) and crawl spaces make this a job for an engineer and a trained installer. Once hazardous-material testing is done you can clear access, move belongings and take photos, but do not enter a crawl space or drill before then.
Laborer or helper
Help only with access, moving belongings and cleanup, and only after hazardous-material testing is done. Do not drill or scan. If you see dust, crumbling concrete or unknown material, stop and tell your lead.
1st-year apprentice
Help with access, scanning, drilling and cleaning under supervision. Do not drill or enter an old building or crawl space until testing is done and the engineer's design is in hand. Learn to recognise poor concrete.
Apprentice, 2nd to 4th year
Drill, clean and set anchors only to the engineer's design and under a journeyperson's direction. Learn to spot cracked or crumbling concrete, and never decide that poor concrete is good enough.
Journeyperson
You own safe access, drilling, cleaning, anchoring and records, following the engineer's design. Stop work and call the engineer if the concrete is cracked or crumbling, the framing does not match the plans, or testing finds hazardous material.
Lead hand or foreman
Confirm testing is cleared before anyone enters and check each hole location against the engineer's design. Cracked or crumbling concrete, framing that differs from the plans, or any hazardous material means work stops and the engineer is called.
Contractor or business owner
Price testing, abatement by licensed trades where needed, the engineer's design and inspection. Get a permit if the work needs one. Agree a written scope with the owner, keep testing reports, the design and photos on file, and confirm liability with your lawyer or insurer.
Starting a new business
Start with a written scope and learn who must do testing and abatement. Subcontract design to an engineer and abatement to licensed trades. Confirm permits, insurance and workers' compensation coverage before your first retrofit job.
By Province:

Retrofit anchoring follows an engineer's design, the product's evaluation report and your provincial building code. Silica, hazardous-material and respirator rules are provincial. I dropped the old per-province list, including its exposure limits, because I could not verify it. Confirm with your OHS regulator and building department.

See Canada by Province for the full comparison.

Sources:

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

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