Corrosion mapping · Montreal
Corrosion mapping in Montreal
Corrosion mapping locates the zones where reinforcing steel is likely corroding in a concrete slab or wall, so that repairs can be targeted in Montreal. In a Montreal parking garage, mapping is organized by level and by area that is actually accessible.
Montreal
Working in Montreal
In a Montreal parking garage, mapping works best when organized by level and by accessible area. Document earlier repairs, leaks and areas exposed to vehicles. Results must remain tied to the grid and the measurement method so that sectors can be compared. The engineer can then determine further investigations and project priorities. The map alone does not constitute a repair specification.
The division by level and by area is worth naming once and for all, from the first pass. A sector renamed between two surveys makes it impossible to say whether its condition changed or only the way it was outlined, which removes the main value of the map.
The state of the surface at the time of the survey is part of the scope. A freshly washed deck, a covering still in place or an area not yet cleared do not read the same way, and the report has to state the conditions under which each sector was examined.
In Montreal, construction, alteration and demolition permits are issued by the boroughs, each of which has its own service counter. If coring or a new opening is part of alteration work, check with the borough concerned.
Preparing your project in Montreal
- Divide the survey by level and by cleared area
- Document earlier repairs and known leaks
- Plan phasing with the manager to keep access open for users
Montreal’s building stock and your concrete surveys
Montreal industrialized along the Lachine Canal. According to Parks Canada, its first industrial boom began in 1848, when the first widening of the canal made a new power source available. More than 600 businesses have occupied the neighbouring land since the canal was built: flour mills, foundries, shipyards, a sugar refinery, then chemicals, petrochemicals and iron and steel production in the western section. The thousands of workers who settled near the factories gave rise to the working-class neighbourhoods of the South-West. Near the canal there are still 40 industrial complexes grouping more than 200 buildings.
On the residential side, Héritage Montréal describes the typical triplex as a building with three civic addresses, often built in series by an owner-developer or a contractor. In the 1920s, many triplexes adopted dark brick facades with artificial stone inserts. They are common in Verdun, the Plateau-Mont-Royal and Rosemont, among others. The early 20th century also brought “shoebox” houses, small one-storey single-family homes, often without a basement, found in Villeray and Hochelaga-Maisonneuve.
Beneath the city, the metro forms another generation of structures. According to the Répertoire du patrimoine culturel du Québec, construction began on May 23, 1962, and the metro opened on October 14, 1966, with 20 stations on two lines. At street level, the City states that it spreads salt and crushed stone as soon as roadways and sidewalks become slippery.
Since the City spreads salt as soon as roadways and sidewalks become slippery, reinforced concrete elements close to the public way receive salty water with every thaw: access ramps, entrance thresholds, steps, balcony slabs facing the street. These contact areas are worth delineating first.
Before a mapping survey, indicate where meltwater runs and pools, which elements have already been patched and where concrete spalling is visible. These markers help the engineer compare sectors rather than read a map in isolation.
Measuring corrosion activity
The ASTM C876 test method covers the estimation of the corrosion potential of uncoated reinforcing steel in concrete, for the purpose of determining its corrosion activity. Taken on a grid, these measurements produce a map of the surveyed surface.
Exposed slabs and parking garages
Parking garages are subject to specific obligations in Quebec: an annual visual verification and an in-depth verification report by an engineer every five years, according to the Régie du bâtiment du Québec. A corrosion map helps locate the zones to watch between these verifications.
- On a cracked or spalled parking slab
- Before planning concrete repairs
- To monitor an area that has already been repaired
Mapping method, process and limitations
How potential measurements work, how the survey runs, how to read the maps and their limitations are covered on our corrosion mapping in Quebec page. This page only covers what is specific to Montreal.
Frequently asked questions
Does corrosion mapping indicate the strength of the structure?
Not directly. It provides information on the corrosion activity of the rebar; assessing structural capacity is an engineer’s responsibility.
Why combine it with a concrete scan?
Ground-penetrating radar locates the rebar and estimates its depth, which helps position corrosion measurements on the steel.
How should a survey in an occupied garage be prepared?
Mark the zones, provide a plan and clarify access with the manager. Phasing must be agreed for the survey scope.
Must every level of a parking garage be mapped?
Not necessarily. The choice of levels and areas depends on observed signs, earlier repairs and the engineer’s needs. Unmeasured areas must be clearly identified in the deliverable.
Sources
- ASTM C876-22b, Standard Test Method for Corrosion Potentials of Uncoated Reinforcing Steel in Concrete
- Régie du bâtiment du Québec: Parking garages, maintenance and inspection
- Ville de Montréal open data: Permis de construction, transformation et démolition (in French)
- Parks Canada, Lachine Canal National Historic Site: The cradle of industrialization
- Parcs Canada: Le berceau de l’industrialisation, French version with the current industrial complexes (in French)
- Héritage Montréal: What is the personality of your home?
- Répertoire du patrimoine culturel du Québec: Inauguration du métro de Montréal (in French)
- Ville de Montréal: Snow removal on sidewalks and streets
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