ZERO LOT LINE (ZLL)
BEST PRACTICE GUIDE
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PAGES 4-7
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CHALLENGES OF ZLL
UTILITIES
EXCAVATIONS
OCCUPIED NEIGHBOURING PROPERTIES/SIDE ENTRANCES
ACCESS PAGE 5
SCAFFOLDING/LADDERS PAGE 6
ROOFING PAGE 6
FENCING PAGE 7
PAGES 8-16
PAGES 8-9
PAGES 10-11
PAGES 11-12
BEST PRACTICES FOR ZLL
UTILITIES
EXCAVATIONS
OCCUPIED NEIGHBOURING PROPERTIES/SIDE ENTRANCES
ACCESS PAGE 12
SCAFFOLDING/LADDERS PAGE 13
ROOFING PAGE 14
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FENCING PAGES 15-16 Page 2 of 17
Zero Lot Line (ZLL) homes are constructed directly on or very near the property boundary, typically with one side yard rather than the two seen in traditional detached homes. Common in urban or higher-density areas, ZLL homes can also be attached forms such as townhomes.
While these homes offer efficient land use, they also present unique challenges during construction. This guide outlines key considerations and best practices to support safe and efficient construction in ZLL developments.
The following outlines the challenges encountered when constructing ZLL homes:
UTILITIES
The limited space on ZLL lots and the close proximity of neighbouring homes create specific utility installation challenges. Improper placement of underground utilities can interfere with the excavation of the ZLL home and create safety hazards for workers. In particular, utility lines that are not “tucked in tight” (eg, gas, electrical, ground plates) or those that jog into adjacent lots can leave tradespeople vulnerable to accidental contact, potentially resulting in injury, significant property damage, and costly delays
Examples of common issues include:
A struck gas line from a neighbouring property due to it jogging into the excavation zone – resulting in gas leaks, evacuation requirements, and service disruptions
A pulled electrical ground plate, which can damage cabling or even pull an electrical panel from an interior wall risking the safety of both trades and residents
Damaged utility lines (gas, electrical, communications) causing service disruptions, delays in backfilling, and requiring involvement of the utility provider for repairs
EXCAVATIONS
Excavating for ZLL homes often requires working right up to the boundary of an alreadydeveloped adjacent lot This increases the potential for:
Exposure of neighbouring foundations.
Disruption to existing landscaping or fencing.
Restricted space for trades once cribbing and foundations are in place.
The previously disturbed soil on the neighbouring lot is less stable than undisturbed soil, presenting sloping and safety challenges. These may require the use of shotcrete or other stabilization techniques to ensure a safe working environment When backfilling, the narrow space between homes restricts equipment size and maneuverability. The presence of structures like gas risers, window wells, or vents increases the risk of accidental damage These challenges are further compounded by poor weather or unstable ground conditions.
Code Reference – National Building Code: 2023 Alberta Edition Division B – Section 8.2 Protection of the Public.
8.2.2.2 Protection of Adjoining Property:
“If the stability of adjoining buildings may be endangered by the work of excavating, adequate underpinning, shoring and bracing shall be provided to prevent: a) Damage to, or movement of, any part of the adjoining building, and b) The creation of a hazard to the public.”
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OCCUPIED NEIGHBOURING PROPERTIES/SIDE ENTRANCES
Due to Zero Lot Line (ZLL) homes being constructed directly at or near the property boundary, additional hazards arise when the adjacent property is occupied especially when that neighbouring home has a side entrance These scenarios require heightened attention to safety, communication, and site coordination.
Potential hazards include:
Unsafe access/egress due to poor housekeeping, uneven terrain, or open excavations adjacent to walkways or side entrances
Risk of falling objects during overhead work (e.g., roofing or exterior finishing above pedestrian routes).
Fencing and site security challenges, including potential unauthorized access to the construction site.
Sloping issues excavators may be forced to maintain access to a side entrance by cutting non-compliant slopes, making it difficult or impossible to meet the legislative requirements outlined in Part 32 of the Alberta Occupational Health and Safety (OHS) Code
ACCESS
ZLL sites often present significant access limitations for trades, equipment, and materials. The narrow working environment reduces available space for storage, movement, and the safe setup of tools and machinery. These constraints can impact productivity, increase ergonomic strain, and raise safety concerns.
Common access-related hazards include:
Introduction of tight and restricted workspaces trades may be forced to operate between excavation banks and structures, making material handling and safe body mechanics more difficult
Minimal clearance between properties posing challenges for the use of equipment like lifts and preventing the proper setup of ladders or scaffolding; full-sized skid steers often cannot access side areas at all.
Housekeeping concerns limited space reduces the ability to store and organize materials safely, leading to cluttered workspaces and tripping or collision hazards.
Code Reference – National Building Code: 2023 Alberta Edition Division B – Section 8.2 Protection of the Public.
8.2.3.1 Safe Passage Past Site:
“Except as provided in Article 8.2.3.2, provisions shall be made at all times for the safe passage of pedestrian and vehicular traffic past the site Material or equipment shall not be placed on any street or other public property except as authorized Except as provided in Sentence (4), where a sidewalk exists adjacent to the site it shall be kept clear of obstructions at all times. Where construction operations necessitate the obstruction of a sidewalk, a temporary sidewalk shall be provided and it shall be kept clear of obstruction at all times”
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SCAFFOLDING/LADDERS
Limited space between homes on Zero Lot Line (ZLL) sites presents significant challenges for trades working vertically. With restricted clearance, there is often inadequate room to safely set up equipment such as ladders or scaffolding These spatial constraints increase the risk of incidents and complicate adherence to safe work practices.
Common hazards associated with vertical work on ZLL sites include:
Inability to set ladders at the recommended 4:1 ratio.
Potential need to encroach or “trespass” onto adjacent occupied properties
Risk to adjacent trades and the public from falling tools, materials, or equipment.
Difficulty maintaining three-point contact on ladders due to restricted space for material installation
Overhead power line exposure and limited clearance during ladder or equipment use.
ROOFING
Roofing, already classified as high-risk work, becomes even more hazardous on ZLL sites due to restricted access and space limitations. These factors can compromise both worker safety and property protection.
Examples of roofing hazards on ZLL sites include:
Poor access/egress for loading or unloading roofing materials
Inability to safely set up a ladder hoist when materials must be dropped at grade.
Limited space for safe operation of mobile equipment (e.g., manlifts, scissor lifts).
Improper or unavailable anchor points for fall protection systems
Risk of materials falling into neighbouring properties or private yards.
Property damage from falling tools, equipment, or materials
Increased potential for falling materials to strike people or other trades in close proximity.
Swing fall risks leading to impacts with lower levels or nearby structures
Proximity to overhead power lines further complicating work zone safety.
Properly installed temporary fencing is a legal and safety requirement to protect the public from the inherent hazards of an active construction site. However, ZLL developments present specific fencing challenges due to the limited working area
Site-specific fencing concerns include:
Increased injury risk from improper lifting techniques due to awkward and tight maneuvering spaces
Insufficient room to install fencing where excavations reach the lot line, potentially requiring attachment to a neighbouring structure.
Limited access/egress where narrow side yards restrict fence placement and interfere with worker movement.
In addition to these ZLL-specific issues, general fencing hazards that exist on all construction sites remain present and are often amplified by the tighter conditions. This increases both the likelihood and severity of incidents
Code Reference – National Building Code: 2023 Alberta Edition
Division B – Section 8 2 Protection of the Public
8.2.1.3 Fencing, Boarding or Barricades:
“When a construction or demolition activity may constitute a hazard to the public and is located 2 m or more from a public way, a strongly constructed fence, boarding or barricade not less than 1 8 m high shall be erected between the site and the public way or open sides of a construction site.
Barricades shall have a reasonably smooth surface facing the public way and shall be without openings, except those required for access
Access openings through barricades shall be equipped with gates that shall be: Kept closed and locked when the site is unattended, and Maintained in place until completion of the construction or demolition activity” (National Building Code: 2023 Alberta Edition)
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UTILITIES
Due to the constrained nature of Zero Lot Line (ZLL) construction sites, careful planning and strict adherence to ground disturbance protocols are critical when working near underground utilities. Improper procedures can result in utility strikes, safety incidents, service interruptions, and significant delays or costs
Recommended best practices for working around utilities include:
All owners, contractors, and subcontractors should be familiar with and adhere to applicable Ground Disturbance policies. These should be shared clearly and reinforced through supervision and site orientations
Valid locates should be obtained before commencing any excavation work. Locates should be reviewed thoroughly, kept onsite at all times, and any discrepancies or concerns should be reported immediately.
Utilities within the designated hand-expose zone should be exposed using nonmechanical means such as hydrovac or hand shoveling mechanical excavation is not permitted in these areas.
Additional permits may be required if working near city streets, alleys, or utility rights-ofway. Confirm requirements with relevant authorities before proceeding.
Utility-Specific Requirements: ENMAX
When working near ENMAX facilities, the following procedures must be followed: Review and follow ENMAX’s Ground Disturbance Guidelines
Prior to any excavation that is within 2 meters of an ENMAX facility, request a Permission Letter by emailing hotdigs@enmax.com.
Notify ENMAX Line Inspection at lineinspection@enmaxcom with intent to excavate near their facilities.
Working Adjacent to Existing Utility Services
When excavating a new foundation adjacent to an existing home, it is critical to assess whether gas and/or electrical services have already been installed on the neighbouring property.
Follow the procedure below based on service installation status:
Confirm with the site supervisor whether the adjacent home had its services (gas/electrical) covered with 40 mm gravel and caution tape at the time of backfill. If services were not properly covered, request a hydrovac of the 4-party utility connection. Afterward, continue to hand-expose the gas line back toward the gas meter
If services were properly covered with gravel and caution tape: Begin excavation by hand-exposing the gas line. Shovel down in 12-inch increments, then use the excavator to remove the loose material.
Once the 40 mm gravel or gas line is visible, continue to hand-expose back toward the meter until the full line is uncovered.
Once the full line is safely exposed and verified, resume standard excavation procedures
During the backfill phase of Zero Lot Line (ZLL) construction, special attention should be given to how gas and electrical services are treated particularly if the area may be disturbed again during future excavation on an adjacent lot Proper backfill procedures are critical for safety, utility protection, and future site coordination.
Ground disturbers should follow these steps:
1 Determine future excavation plans:
Assess whether the side of the house containing gas and/or electrical services will be excavated again for an adjacent foundation.
If no further excavation is expected, backfill according to standard procedures
If future excavation is planned, continue with the additional protective steps below.
2 Secure utility placement:
Confirm the gas line is installed and secured near the footing in a location safe for backfill.
If the gas line is not in a safe or appropriate location, do not proceed Immediately notify the home builder’s supervisor so the appropriate utility provider can correct the line placement
3.Backfill procedure for 4-party lines:
Begin backfilling the side yard above the 4-party utility lines using approved material in line with ENMAX’s Backfill Standards
If approaching a utility right-of-way, ensure all required notifications have been made as per the ENMAX Ground Disturbance Guidelines
4.Service trench treatment:
When services enter from the rear of the home, cover the gas line with 40 mm gravel up to the back of the excavation stopping at the utility trench
Place caution tape directly on top of the gravel to mark the utility line location and enhance future visibility
5.Documentation:
Once the gas line is in a safe position and properly covered, take a photograph of the side yard showing the final location of the gas line for documentation and future reference.
6.Final backfill:
Complete the backfill process in accordance with all applicable Ground Disturbance policies, Utility Codes, and Canadian Electrical Code standards.
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All excavation work regardless of housing type should follow recognized best practices and comply with Part 32: Excavating and Tunnelling of the Alberta Occupational Health and Safety (OHS) Code Ensuring site safety before, during, and after excavation is critical, particularly in the context of Zero Lot Line (ZLL) developments where space constraints are significant
Prior to excavation, the following measures should be taken:
Install temporary fencing around the anticipated excavation area to protect workers and the public.
Complete utility locates in advance and keep on site for reference by the excavation team
Secure fencing to ensure it cannot fall into the excavation during work.
The site manager should notify adjacent homeowners of upcoming excavation activities, including the potential need to remove existing fencing on shared property lines.
Fence Removal and Safety Planning
Once the excavation area has been staked or surveyed, the site supervisor should evaluate whether adjacent fencing needs to be removed in order to perform the work safely.
Consider the following conditions when making this determination:
If the excavation depth is greater than 15 metres, and the soil is hard and compact but likely to crack or crumble, the neighbouring fence should be removed wherever possible to reduce the risk of collapse or injury
If the soil is classified as soft, sandy, or loose, the excavation walls should be sloped at a minimum angle of 45 degrees from the base to meet safety standards. If fence removal is not feasible, an engineered shoring system should be installed to ensure safe excavation in compliance with applicable code requirements. In cases where the excavation undermines the structural integrity of a neighbouring fence, the fence should either be removed, or an engineered solution be implemented. By following these practices, site supervisors can mitigate risks associated with excavation on ZLL lots and ensure compliance with safety legislation Early planning and communication with neighbours, utility providers, and excavation crews are essential for safe and successful project execution
EXCAVATIONS (CONTINUED)
Additional Excavation Safety Requirements
To maintain safe working conditions throughout excavation, the following measures should also be observed:
Cut heights and slopes should be maintained in accordance with Part 32 of the Alberta OHS Code, based on the specific soil type present.
The excavation should be kept free of standing water, which can introduce additional hazards such as slips, instability, or collapse.
If grading or downspout placement causes water to flow toward the excavation edge, steps should be taken to redirect runoff away from the excavation.
A safe means of entry and exit such as ladders or designated access points should be provided and maintained for all personnel entering or leaving the excavation
Spoil piles should be placed at least 1 meter away from the edge of the excavation, and any loose material scaled or trimmed from the walls to prevent collapse or injury
OCCUPIED NEIGHBOURING PROPERTIES/SIDE ENTRANCES
Zero Lot Line (ZLL) construction often involves work immediately adjacent to occupied properties, including homes with side entrances These situations require careful planning and proactive communication to ensure the safety of residents and workers, as well as compliance with safety codes
Before excavation or construction begins, the following steps should be taken: Conduct a lot inspection to identify potential access, excavation, and safety challenges.
Notify neighbouring homeowners of the planned excavation start date and expected duration of work. This should be done a minimum of 48 hours in advance.
If the neighbouring home has a side entrance that will be impacted, communicate early and work with the resident to determine alternate access options
Where possible, coordinate interior access through the home to temporarily bypass the side yard.
If access through the home is agreed upon, the side entrance should be blocked during the construction period for safety and security. If access through the home is not possible, the builder should coordinate either: temporary accommodations (e.g., hotel) for the occupant, or the installation of a safe scaffolding system to maintain access during excavation and construction
The excavation contractor should notify the builder if the planned excavation cut height may exceed limits outlined in the Alberta OHS Code Upon notification, the builder is responsible for arranging an appropriate protective system (e.g., engineered shoring, shotcrete) to ensure the site remains safe and compliant Page 11 of 17
OCCUPIED NEIGHBOURING PROPERTIES/SIDE ENTRANCES (CONT.)
Additional Safety Considerations:
Cordon off high-risk areas using pylons, signage, and hazard tape where there is potential for public or worker exposure
Be aware of the potential for harassment or conflict with neighbours. Workers should not engage with aggressive individuals. Report any concerns to a supervisor immediately and, if needed, leave the area to prevent escalation
Overhead work hazards may occur during framing, roofing, or material handling. Install appropriate signage and overhead protection where required
Maintain clear housekeeping practices along the side entrance throughout the duration of construction to avoid slips, trips, and obstructions.
Temporary fencing should be adjusted as needed to allow safe access and egress at the side entrance, without compromising site security.
Install gravel or other stable surfacing to provide a defined, safe path of travel for the homeowner or basement tenant if the side entrance is to remain in use.
When working on ZLL sites with occupied neighbouring properties and side entrances, all efforts should be made to maintain safe conditions and uphold respectful, proactive communication with affected homeowners.
ACCESS
Access can be a significant challenge on Zero Lot Line (ZLL) sites due to the limited space between structures and constrained working areas When access is restricted, it is essential that discussions take place with all involved parties to assess conditions and implement appropriate safety measures
The following best practices should be followed to reduce hazards and support safe site navigation:
Utilize shotcrete, shoring, or other means of protection to support soil integrity in narrow spaces between buildings and excavated banks.
Maintain clear and organized work areas through consistent housekeeping to minimize clutter and ease movement
Select tools and equipment suited to tight working conditions for example, mini skid steers, compact platforms, or narrow scaffolding
Plan and schedule trades strategically to avoid overlapping activities in confined areas and ensure safe, efficient progress.
Maintain frequent communication among site supervisors, trades, and contractors to coordinate access routes and address challenges as they arise.
Install and maintain safe walkways and temporary structures, such as stable ramps or steps, to provide secure access in and out of excavation areas.
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SCAFFOLDING/LADDERS
Due to the confined nature of Zero Lot Line (ZLL) sites, careful planning and setup of scaffolding and ladders is essential to ensure worker safety and compliance with legislation
When erecting scaffolding or setting up ladders, the following best practices should be followed:
Erect scaffold poles parallel to the structure to maintain stability and prevent encroachment into neighbouring lots.
Do not place poles inside open excavations, holes, or ditches, as this creates a significant fall and collapse hazard
Ensure side yards are clear of debris and the ground is level and stable before setting up any equipment
Position scaffold poles to ensure clearance over the neighbouring home’s roofline, especially when working at height.
Place ladders against the adjacent basement wall where possible to achieve the lowest safe slope and allow safe access to the scaffolding platform.
Remove or secure ladders when not in use Ladders should be either taken off-site or lowered and locked to prevent unauthorized access or misuse.
When setting up near energized lines, follow Part 17 – Safe Limits of Approach Distance for Overhead Power Lines as outlined in the Alberta Occupational Health and Safety Code.
Roofing is considered high-hazard work, and the risks are amplified on Zero Lot Line (ZLL) sites due to space constraints, proximity to adjacent homes, and limited access. Proper planning, equipment use, and housekeeping are essential to maintain a safe work environment.
The following best practices should be followed for roofing work on ZLL sites:
Be aware of your physical limitations and the weight of materials being handled Seek assistance when lifting or carrying heavy objects. Where possible, utilize mechanical lifting devices or powered equipment to move materials Due to restricted access, compact or narrow machinery may be required Ensure all materials are secured and accounted for during loading, unloading, and installation Take corrective action immediately if any material becomes loose or unstable.
Clearly cordon off high-risk areas using pylons, signage, and hazard tape particularly where there is potential for falling material Use overhead work signage to alert workers and the public as needed.
Check that all tools and equipment left at ground level are properly secured and do not pose tripping or access hazards during travel to and from the roof.
On the roof deck, ensure all tools, materials, and equipment are securely stored to prevent falls from height
Maintain clean working conditions by regularly removing loose materials from the roof deck throughout the day At the end of each shift, perform a final clean-up removing all debris and organizing materials into a designated pile or bin. Before leaving site, conduct a final inspection to confirm that all access points are secured Ladders should be removed or lowered and locked to prevent unauthorized use.
Proper fencing is essential for protecting the public, trades, and adjacent properties on Zero Lot Line (ZLL) sites Due to the proximity of construction activities to neighbouring homes, walkways, and public spaces, fencing should be carefully planned, installed, and maintained throughout the build process
The following best practices should be implemented when setting up and managing fencing:
Ensure fencing runs the entire perimeter of the construction area and is adequately braced to withstand wind and potential impact.
Use all required fencing components, securely fastened to prevent the fence from opening, collapsing, or becoming unstable
Take steps to eliminate any gaps or openings between fencing panels to maintain a secure enclosure
Install a designated access point that allows workers to enter and exit safely, without obstructing roads, sidewalks, or pathways.
Additional considerations include:
Fencing should be installed prior to any excavation activities begins
Fencing should remain in place until lockup, when openings up to 3m above grade are secured from entry, shingling is complete, and all climbable structures have been removed or lowered to the ground and secured.
Note: Houses under construction around areas where the public are expected like occupied homes, playgrounds, parks and public pathways the fence should remain in place until all exterior overhead construction is complete.
Fencing is considered an enclosure when it is continually connected and/or placed within 8 inches of a solid structure and encompasses the entire work site.
Fencing may be required to remain in place to protect municipally owned trees under The City of Calgary Tree Protection Bylaw
If access to a neighbouring property is required to ensure safe installation of fencing, permission should be sought from the property owner or designated representative prior to commencing activity.
If the neighbouring house has a fence, deck, side entrance etc. that may be a concern, the site supervisor should contact the safety representative and/or the construction manager to inspect the site prior to excavation and take photos of the concerning items
Workers should be instructed on the safe handling of fencing panels (proper ergonomics).
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FENCING (CONT.)
Fencing should not restrict public access to amenities, sidewalks and services, including access to fire hydrants.
Signage should provide contractor and site information to the public on any site requiring safety fencing The signage should contain relevant information including builder name and emergency contact, Building Permit number and site address. Signage should be clearly visible from the street
Fencing should not restrict emergency personnel from accessing emergency response resources.
Fencing may remain open while workers are physically on site but should be installed and secured any time the site is left unattended
National Building Code – 2023 Alberta Edition
CSA C22.1:24 Canadian Electrical Code 26th Edition
Alberta Electrical Utility Code, 6th Edition, 2022
Alberta Occupational Health and Safety Code (2024)
Part 17 Overhead Power Lines - Safe limit of approach distances
Part 32 Excavating and Tunneling
ENMAX Ground Disturbance Guidelines
City of Calgary Tree Protection Bylaw Page 16 of 17