Case Study Overview
How Rimkus Delivered Construction Administration for Underground Parking Garage, Podium Deck, Ramp, and Retaining Wall Rehabilitation at an Occupied Residential Community in Thornhill, Ontario
Rimkus Building Sciences provided construction administration for a full parking garage, ramp, and deck rehabilitation at Thornhill Green, an affordable residential community in Thornhill, Ontario — delivering 17 field reviews, five construction change orders, and five payment certificates from mobilization through holdback release for Housing York Inc. and the Regional Municipality of York.
A Rimkus Building Sciences engagement for Housing York Inc. and the Regional Municipality of York delivered construction administration for a comprehensive rehabilitation program at Thornhill Green in Thornhill, Ontario: underground parking garage repairs, podium deck waterproofing and resurfacing, heated ramp reconstruction, Sienastone retaining wall replacement, staircase rehabilitation, and associated drainage and safety upgrades across an occupied affordable housing community of 101 townhouse units. Rimkus conducted 17 field reviews from November 2023 through May 2024, administered five construction change orders, and issued five payment certificates including holdback release in October 2024.
We serve affordable housing providers, municipal housing corporations, property managers, building owners, and institutional asset managers requiring technical consulting for parking garage rehabilitation, building envelope condition assessment, reserve fund studies, and construction administration across residential and commercial properties throughout Canada.
Who this is for: Affordable housing providers, municipal housing corporations, property managers, and institutional asset managers planning parking garage, deck, or ramp rehabilitation on occupied residential communities requiring independent construction oversight, change order administration, and payment certification.
What We Did
- Provided construction administration for the full rehabilitation program: underground parking garage repairs, podium deck waterproofing, heated ramp reconstruction, retaining wall replacement, staircase rehabilitation, and associated safety upgrades.
- Conducted 17 field reviews from mobilization (November 6, 2023) through final site visit (May 24, 2024), documenting progress and directing corrective actions at each milestone.
- Administered five construction change orders covering additional scope, and issued five payment certificates including 10% holdback release in October 2024.
How We Helped
- Provided independent oversight of waterproofing installation, concrete repairs, ramp reconstruction, and retaining wall replacement across an occupied site, maintaining continued resident parking access throughout construction.
- Identified and directed correction of construction deficiencies including residual asphalt on sidewalks, wet slab conditions preventing sealer application, and incomplete painting at column bases before final acceptance.
- Administered scope additions for unanticipated work, including additional concrete repairs, new slab waterproofing across 9,040 sf, and staircase heating cable replacement, and returned unused provisional and cash allowance credits through Change Order 5.
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SERVICE LINES |
SECTOR |
LOCATION |
ENGAGEMENT LEAD |
|---|---|---|---|
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Building Sciences |
Affordable Housing / Municipal |
Thornhill, Ontario |
Marc Winters, P.Eng. — Rimkus BES, Canada |
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17 |
5 |
5 |
101 |
|---|---|---|---|
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FIELD REVIEWS |
CHANGE ORDERS |
PAYMENT CERTS |
TOWNHOUSE UNITS |
What Was the Challenge? Aging Parking Infrastructure at an Occupied Affordable Housing Community
Thornhill Green is an affordable residential community of 101 townhouse units in Thornhill, Ontario, constructed circa 1966. The property includes a one-level underground parking garage with a podium deck above serving as additional surface parking, a vehicle ramp, and two retaining walls on the east side of the property.
A prior evaluation had identified the parking infrastructure as having reached the end of its useful life: the podium deck exhibited localized deterioration and water leakage, the ramp surface showed widespread cracking and was in poor condition, the stairwell was in poor condition, the expansion joint at the parking garage-ramp retaining wall required replacement, and the existing garage louver was inadequate for minimum airflow requirements. The Region concluded that full rehabilitation was required.
The challenge for Housing York Inc. and the Regional Municipality of York was overseeing a complex, multi-system rehabilitation program across an occupied residential site, maintaining resident access to parking throughout construction, coordinating work across the underground garage, podium deck, ramp, and retaining wall areas, and verifying that specified materials and installation standards were met at each phase. Rimkus was engaged to provide independent construction administration throughout.
“Parking garage rehabilitation on an occupied affordable housing site requires construction administration that keeps residents informed and maintains site access throughout. On this project, 17 field reviews across six months documented progress and directed corrective actions at every construction phase.” – Chander Thusu, B.Eng., BSS, Practice Leader, Building Sciences
How Did Rimkus Help? Construction Administration Across a Multi-System Rehabilitation
Rimkus was engaged to provide construction administration services for the full rehabilitation program, serving as independent contract administrator on behalf of Housing York Inc. and the Regional Municipality of York.
Field Reviews and Site Oversight |
Payment Certification |
|---|---|
|
Conducted 17 field reviews from mobilization on November 6, 2023 through the final site visit on May 24, 2024. Each visit documented construction progress across the underground garage, podium deck, ramp, and retaining wall areas, and directed corrective actions where required. Field review reports were distributed to the Regional Municipality of York and Housing York Inc. following each visit. |
Reviewed contractor invoices and issued five payment certificates: PC1 (December 19, 2023), PC2 (January 11, 2024), PC3 (May 9, 2024), PC4 (July 17, 2024), and PC5 (October 15, 2024). PC5 was the 10% holdback release, recommended subject to confirmation that the 60-day period had expired and no liens had been registered against the property. |
Change Order Administration |
Occupied-Site Coordination |
|
Administered five construction change orders covering unanticipated scope additions and end-of-project credit adjustments. Change orders addressed items including additional concrete repairs, staircase heating cable replacement, additional drainage, new guardrails, expanded waterproofing coverage, and the return of unused provisional items and cash allowances. |
Construction was administered on an active, occupied residential site. Field review reports documented contractor adherence to working hours (Monday to Friday, 8am to 5pm), site hoarding requirements, and coordination with property management to maintain resident access to parking throughout construction. |
How Our Services Address Common Challenges
Common Challenge |
What Rimkus Provides |
|---|---|
|
Verifying waterproofing and concrete repair quality on occupied parking structures |
Regular field reviews at critical installation milestones document material application, surface preparation, and installation sequence before subsequent work proceeds |
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Unanticipated scope requiring documented change order administration |
Prepared and administered construction change orders with itemized scope descriptions and unit rates, reviewed and approved by the owner before work proceeded |
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Payment certification on multi-phase occupied-site construction |
Reviewed contractor invoices against work completed to date; certified payment amounts and issued formal payment certificates with supporting documentation to the owner |
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Contractor deficiency management on occupied residential sites |
Deficiencies documented with photographic evidence in field review reports; contractors directed to rectify before demobilization or before subsequent work proceeded |
Deliverables: What Housing York Inc. and York Region Received
- 17 formal field review reports documenting construction progress, material installations, and directed corrective actions across all work areas
- Payment Certificate No. 1 (December 19, 2023): recommended payment of $269,566.02 (taxes incl.) to Quality Connect Construction Inc.
- Payment Certificate No. 2 (January 11, 2024): recommended payment of $152,960.53 (taxes incl.)
- Payment Certificate No. 3 (May 9, 2024): recommended payment of $155,624.73 (taxes incl.)
- Payment Certificate No. 4 (July 17, 2024): recommended payment of $50,374.04 (taxes incl.)
- Payment Certificate No. 5 (October 15, 2024): recommended 10% holdback release of $72,244.29 (taxes incl.), subject to confirmation of lien period expiry
- Five construction change orders: CO1 (staircase work, drain, handrails, +$29,800), CO2 (additional concrete repairs, electrical, +$22,940), CO3 (chain-link fence and access control), CO4 (parking markings, signage, Tremco waterproofing 9,040 sf, +$47,540), CO5 (unused provisional items and cash allowance credits, -$98,300)
- Progress meeting minutes (November 21, 2023) documenting construction coordination, outstanding items, and contractor direction
Technical Scope of Work
The rehabilitation program addressed the following systems at the Thornhill Green parking facility, with Rimkus providing construction administration oversight across all work areas:
- Podium Deck: Demolition of existing asphalt overburden; concrete repair of topside deck surface including crack sealing and localized repairs; application of below-grade waterproofing membrane within exterior walls; new waterproofing system (Tremco) applied to full podium deck slab (9,040 sf, CO4); new base course asphalt (HL8) on podium deck surface; new 4″ diameter surface drain at low point.
- Underground Parking Garage: Vertical concrete repairs to foundation walls; two coats of crystalline waterproofing mortar applied to perimeter foundation walls; crack sealing on slab on grade using Sikadur Hi-Mod 32 with Sika 122; application of concrete sealer (EUCLID ULTRASIL LI+) to slab surface; painting of all interior garage wall surfaces; installation of new wiring to connect new lights to main panel.
- Heated Vehicle Ramp: Excavation and removal of existing asphalt along ramp area; removal of deteriorated parging and existing paint from ramp walls; application of new Mapei wall coating; new heated concrete ramp installation (provisional item, approved by York Region).
- Staircase Rehabilitation: Removal of existing soil within staircase roof slab walls; replacement of existing staircase heating cables; installation of new galvanized steel handrails on both sides of staircase walls (length and location to match existing).
- Retaining Wall Replacement: Removal of existing retaining walls on the east side of the property; compaction testing of subgrade soil; installation of new Sienastone concrete unit retaining walls; new guardrail installation along ramp wall with anchors, nuts, and washers at each base plate connection; drilling of new railing into Sienastone retaining walls at 6-Block and 7-Block.
- Chain-Link Fencing and Access Control: Removal of existing chain-link fence within parking garage structure; supply and installation of new chain-link fence with new access gate; provision of 30 new garage access key fobs and new garage door sensors with wiring and installation.
- Painting and Finishing: Interior garage walls and columns painted; roof slab walls painted to match adjacent existing colour; painted grille on wall at bottom landing of staircase; parking lot lines and restricted parking fire lines painted (temporary and permanent); new parking sign installed.
The Process: Construction Administration Across 17 Field Reviews
Rimkus provided construction administration from mobilization through holdback release, with 17 field reviews conducted between November 2023 and May 2024.
- FR 1 (November 6, 2023): Contractor mobilized; 6-foot steel hoarding fence installed around work area. Asphalt overburden removal from podium deck surface commenced. Contractor directed to post required Ministry of Labour project signs and to install shoring under suspended roof deck as required by specifications.
- FRs 2-4 (November 2023): Continued asphalt overburden removal and deck surface preparation. Crack sealing and concrete repairs to podium deck surface completed. Contractor prepared surface for waterproofing installation; base course asphalt scheduled.
- FR 5 (November 27, 2023): Concrete repairs to podium deck surface complete; deck ready for waterproofing. Excavation and asphalt removal commenced on ramp; ramp wall parging and paint removed. Existing retaining walls on east side removed; compaction testing completed. Sienastone installation planned for the following week.
- FRs 6-8 (December 2023): Waterproofing applied to podium deck and exterior walls of stairwell and air shaft. Retaining wall installation progressed. Ramp wall coating work continued. CO1 issued (December 4, 2023): staircase soil removal, heating cable replacement, new 4″ drain, new galvanized steel handrails.
- FR 9 (January 8, 2024): HL8 base course asphalt completed on podium deck; parking lot returned to service. Foundation wall vertical concrete repairs complete; two coats of crystalline waterproofing mortar applied. Garage power-washed in preparation for painting. Deficiency: residual asphalt on adjacent sidewalk directed for removal before demobilization. CO2 issued (January 3, 2024): additional concrete repairs, temporary parking line painting, and electrical wiring.
- FRs 10-12 (January-February 2024): Interior garage painting commenced and progressed. Ramp waterproofing and coating work continued. Guardrail installation on ramp wall progressed. Retaining wall work continued.
- FR 13 (February 12, 2024): Guardrail installation on ramp wall progressing; anchors, nuts, and washers installed at base plate connections. Slab on grade cracks sealed with Sikadur Hi-Mod 32. Deficiency: garage slab surface wet with water appearing from beneath the concrete slab; Contractor directed to wait for dry surface before applying EUCLID ULTRASIL LI+ sealer.
- FRs 14-16 (March-April 2024): Slab sealer application completed once surface dried. CO3 issued (April 24, 2024): chain-link fence replacement and 30 new garage access key fobs and door sensors. CO4 issued (July 29, 2024): parking line painting, new parking sign, new Tremco waterproofing on full podium slab (9,040 sf). CO5 issued (July 25, 2024): credits for unused provisional items and cash allowances (-$98,300 excl. HST).
- FR 17 (May 24, 2024): Substantial completion review. Roof slab walls painted to match adjacent colour. Staircase grille painted. New railing drilled into Sienastone retaining walls at 6-Block and 7-Block. Deficiency: fence abrading sprinkler pipe (directed for adjustment). Deficiency: column base not painted at one location (directed for completion before final acceptance).
- Payment Certificate No. 5 (October 15, 2024): 10% holdback release recommended. PC5 recommended payment of $72,244.29 (taxes incl.) to Quality Connect Construction Inc., subject to Housing York Inc./York Region confirming the 60-day lien period had expired and no liens were registered against the property.
Notes on Methods and Limitations
Field reviews are discrete site observations and do not constitute continuous inspection. The contractor remains solely responsible for on-site health and safety, fire hazard management, and compliance with all applicable laws and regulations. Payment certificate amounts are based on work completed to date as observed and confirmed during site reviews; they are recommendations to the owner for payment approval.
“Construction administration on occupied affordable housing is as much about maintaining resident confidence as it is about verifying construction quality. Seventeen field reviews provided Housing York Inc. and York Region with a documented record of every milestone, every deficiency, and every corrective action taken.” – Chander Thusu, B.Eng., BSS, Practice Leader, Building Sciences
Key Observations and Corrective Actions
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Observation |
Condition |
Direction and Outcome |
|---|---|---|
|
Residual asphalt on sidewalk |
Contractor left residual asphalt on adjacent sidewalk following HL8 asphalt installation on podium deck (FR 9) |
Directed for removal before contractor demobilization from site |
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Slab surface wet during sealer application |
Garage slab surface found to be wet with water appearing from beneath the concrete when EUCLID ULTRASIL LI+ sealer was to be applied (FR 13) |
Contractor directed to wait for dry surface conditions before applying sealer; slab sealer subsequently completed |
|
Field-welded guardrail burn marks |
Field welding of guardrail on ramp wall left burn marks on metal surface (FR 13) |
Contractor applied paint over burn marks to achieve an aesthetically appropriate finish at weld connections |
|
Fence abrading sprinkler pipe |
Chain-link fence at bottom landing of staircase found to be in contact with and abrading the sprinkler pipe (FR 17) |
Contractor directed to adjust fence to prevent ongoing contact and damage to the sprinkler pipe |
|
Column base unpainted |
Back of column at one location not painted black at the base as required (FR 17) |
Contractor directed to complete painting at this location before final acceptance |
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Retaining wall soil bearing verification |
Following removal of existing retaining walls, confirmation of soil bearing capacity required before new Sienastone wall installation |
Contractor directed to provide compaction test results; testing completed and installation of Sienastone units confirmed to proceed |
Construction Administration Note: Deficiencies on this project were operational in nature: residual materials, incomplete finishes, and minor sequencing issues, rather than structural. All were identified through field review observation and directed for correction before final acceptance. The documented record of each observation and direction provides Housing York Inc. and York Region with a clear account of the construction administration performed on their behalf.
The Value Delivered
Independent construction administration on a multi-system rehabilitation of this scale delivers value at every phase: in the documented record of what was installed, the independent verification of payment amounts, and the transparent administration of scope changes.
Results Summary
- 17 field reviews conducted from mobilization (November 6, 2023) through final site visit (May 24, 2024) across all work areas: underground garage, podium deck, ramp, staircase, and retaining walls.
- 5 construction change orders administered, including $98,300 in credits returned to the owner through Change Order 5 for unused provisional items and cash allowances.
- 5 payment certificates issued, covering all progress payments and the 10% holdback release (October 15, 2024).
- All deficiencies identified through field review directed for correction before final acceptance.
Independent payment certification on a complex multi-phase program. Five payment certificates were issued over the construction program, each based on independent review of contractor invoices against work completed to date. The holdback release certificate (PC5) included the formal recommendation and conditions for release, protecting Housing York Inc. and York Region’s interests under the applicable holdback requirements.
Transparent change order administration returned unused allowances to the owner. Change Order 5 returned $98,300 (excl. HST) in unused provisional items and cash allowances to Housing York Inc. and York Region. Transparent change order administration means that scope not used is credited back rather than absorbed, and that every addition to scope is documented with itemized descriptions and unit rates before work proceeds.
Documented construction record across all work areas. Seventeen field review reports provide Housing York Inc. and York Region with a documented record of construction progress across the underground garage, podium deck, vehicle ramp, staircase, and retaining wall areas, including photographic evidence of installed conditions and a written account of every directive issued to the contractor.
Continuous access maintained for residents throughout construction. Field reviews documented contractor adherence to working hours, hoarding requirements, and the phased approach that returned the parking lot to resident service following podium deck resurfacing, with remaining work proceeding in areas that did not interrupt resident access.
Why Rimkus Built Environment Solutions
Parking garage and deck rehabilitation on occupied affordable housing requires a construction administrator who understands both the technical requirements of the work and the operational constraints of a residential site. Rimkus Building Sciences provides independent field review, payment certification, and change order administration that gives housing providers and municipal clients the documented evidence they need: that the work was done to specification, that payments are supported by verified completion, and that scope changes are administered transparently.
For Housing York Inc., York Region, and similar institutional housing clients, the value of independent construction administration is not only quality assurance — it is the auditable record of how public dollars were spent and what the community received in return.
Key Takeaways for Affordable Housing Providers and Municipal Asset Managers
What Every Affordable Housing Provider and Municipal Asset Manager Should Know
- Independent construction administration on parking garage rehabilitation provides the housing provider with an objective record of what was installed, when, and to what standard, separate from the contractor’s own account.
- Payment certification based on independent field review protects the owner: payments are recommended only when work has been verified as representative of the amount claimed, and holdback release is conditional on confirmed lien period expiry.
- Transparent change order administration means that unused provisional items and cash allowances are credited back to the owner. On this project, $98,300 (excl. HST) was returned through Change Order 5.
- On occupied affordable housing sites, construction must be phased to maintain resident access throughout. Field reviews document that working hours, hoarding, and site access requirements are being followed, not just the quality of the construction work.
- A multi-system parking garage rehabilitation involves simultaneous work on waterproofing, concrete, drainage, heating, electrical, fencing, and finishes. Construction administration that covers all work areas, not just the primary scope: it protects the owner against deficiencies in secondary or finishing work.
Related Services
- Building Sciences Consulting
- Parking Garage and Deck Rehabilitation
- Construction Administration
- Reserve Fund Studies and Condition Assessments
- Specification Writing and Tender Management
Frequently Asked Questions
Connect with Our Expert
Chander Thusu, B.Eng., BSS
Practice Leader, Building Sciences
+1 416 970 3107
[email protected]
View Chander’s Expert Profile
Chander has 32 years of experience in building sciences, structural rehabilitation of parking and balcony structures, and forensic investigation of high-humid buildings such as swimming pools and steam rooms. He holds a Building Science Specialist (BSS) designation from the Ontario Building Envelope Council and a Building Science Certificate from the University of Toronto.
This case study is intended to provide general information and insights into prevailing industry practices. It is not intended to constitute, and should not be relied upon as, legal, technical, or professional advice. The content does not replace consultation with a qualified expert or professional regarding the specific facts and circumstances of any particular matter.