Template:Part 14 (Waterproofing Roofs)

1 General

This Part covers the design and installation requirements for roofs that support an overburden, whether it is structurally supported or non-structurally situated on the roof platform. These overburdens include
1. Roof Coverings (including, without limitation)
  1. gravel ballast.
  2. wearing surfaces and living spaces (rooftop terraces) – pavers, wood or composite decks and walkways, cast-in-place concrete, rubberized surfaces and playscapes, pet relief areas.
  3. gardens/vegetated assemblies (modular and built-in-place).
2. Structures and Equipment (including, without limitation)
  1. planters.
  2. furnishings.
  3. hot tubs.
  4. gazebos, pergolas, nets and wind screens.
  5. housekeeping pads.
  6. photovoltaics.
  7. elevated walkways and stairs; satellite equipment; light standards; signage; lightning rods; sculptures.
  8. structural planters, pools and other water features.
3. Any covering, structure or item of equipment must be installed in a manner that protects the roof membrane and its performance.
4. Coverage under the RoofStar Guarantee may be affected by roof coverings or equipment that impede access to the roof assembly. Refer to Section 1 in this Manual.

1.1 Definitions

Refer to the Glossary for further definitions of key terms used in this Manual.

Extensive Vegetated Roof Assemblies

sometimes referred to as 'eco-roofs', 'low-profile green roofs,' ' rooftop gardens' or simply as 'green roofs',

are installed and maintained without the use of penetrating hand tools.
utilize pre-assembled trays, boxes, mats or other contained soil or media.
have minimal plant species diversity.
are irrigated only to establish plants.
have a soil depth no more than 150 mm (6").
are not normally accessed by building occupants.


Inaccessible Overburden: refers to overburden that must be demolished in order to access the roof membrane. A concrete split slab is a type of inaccessible overburden.

Overburden: (also referred to as a wearing course or layer) is a covering, structure or item of equipment that is situated on top of, and covering all or a portion of, a completed roof or waterproofing membrane assembly. Overburden includes, without limitation,

Roof Coverings

loose growing media, gravel (used as a covering, not exclusively as ballast), sand or any other granular material.
void fill.
tiles, pavers, supporting pedestals or other similar materials.
vegetated assemblies in trays, mats, other similar containers.
cast-in-place concrete.
playing surfaces.
pet relief areas.

Structures

planters, inclusive of everything they contain
gazebos, decks, benches.
water features & hot tubs.

Equipment

satellite / Communications.
lightning rods.
photovoltaics.
signage and lighting.


Roof Platform: refers to a roof assembly which supports an overburden or living (amenity) space consisting of coverings, structures or equipment that are not part of the assembly.

1.2 Design

Membrane Roof Assemblies may be utilized for more than simple weather protection; they can be occupied by casual or regular users, for gardening, playing, lounging, or other leisure activities. Roofs that serve as amenity spaces require that the Design Authority pay particular attention to the assembly selection itself and, especially, to the protection of the roof membrane.

A conventional roof membrane assembly is not appropriate for all types of use or roof coverings. For example, the designed live loading for occupied spaces, or the weight of a roof covering, may require the Design Authority to specify particular materials, and consequently to design a roof as a Protected Membrane Roof Assembly. Furthermore, some roof coverings require maintenance that may result in damage to conventionally insulated assemblies; protected membrane roofs shield the sensitive membrane from this inevitability.

A Protected Membrane Roof Assembly (often referred to as an ‘inverted roof’) offers the designer many benefits, including

longer lasting membranes.
capacity for heavier dead and live loads.
only one control layer to seal and join with the rest of the building envelope.
fewer waterproofing challenges around penetrations.
the capacity for electronic leak detection (whether passive or monitored).

For RoofStar Guarantee Standards pertaining to the securement of a ballasted Protected Membrane Roof Assembly, refer to 3 SECURING the ROOF ASSEMBLY, 3.3.2 Ballasted Roof Assemblies (PMRAs and MPMRAs).

Criteria for evaluating the sensitivity of building interiors is left to the Design Authority.

This Subsection is written to provide guidance by way of general Standards and Guiding Principles, to assist the Design Authority in making the best possible choices for the roof assembly.

1.2.1 General

The building structure must be designed to support any live loads required under the building code having jurisdiction, together with the loads from any covering, amenity space, structure or live loads superimposed upon the roof platform.
The Design Authority should give thought to the inevitability of roof repairs or replacement when designing the coverings, living spaces or structures the roof will support. This includes, without limitation,
1. access for maintenance.
2. material removal, storage and replacement logistics.
The Design Authority is responsible for the appropriate securement design of coverings, living (amenity) spaces and structures, to resist anticipated wind loads. Where structural securement is desirable or required, it must be made to fully waterproofed structural supports (curbs, sleepers, posts) and must be secured to the structural support at least 200 mm (8”) above the water plane. See 11 PENETRATIONS and DRAINS. See also 3 SECURING the ROOF ASSEMBLY.
A roof designed and constructed as a Protected Membrane Roof is strongly recommended when the roof covering or living (amenity) space
1. exceeds 150 mm (6”) in depth (excluding any plants).
2. is an intensive or semi-intensive vegetated system.
3. includes cast-in-place concrete surfaces.
4. is installed over a podium roof area adjacent to residential high rise structures.
5. includes water features or pools.
6. includes expansive terrace areas or play spaces.
Roofs designed as platforms for coverings, amenity spaces and equipment must take into account the following Standards and Guiding Principles:
1. Load bearing:
  1. Non-structural installations - Insulation and insulation overlays used in a conventional or modified protected membrane roof system must have a minimum load carrying capacity of 110 Kpa (20 psi), but in any event must be capable of supporting any superimposed loads on the exposed membrane, without compression or distortion of the roof system or any one of its components. Otherwise, the roof platform must be designed as a PMRA. See also 8.1.1 Design (Insulation Overlays).
  2. Structural installations - structural supports (i.e. curbs) should be considered to bear heavier dead loads, to resist specified wind loads, or to secure the equipment during seismic events.
2. Membrane thickness and puncture resistance: Membranes must be selected for their ability to resist accidental puncture by human activity on the roof; the minimum puncture resistance must be at least 400 N. Refer to the table in 9.1.2 for minimum membrane thickness and puncture resistance requirements.
3. Protection:
  1. Membranes must be protected from damage incurred
    1. during the construction of a building.
    2. from normal use and occupancy of the roof.
    3. from maintenance of any installation on top of a roof system, after the building has been commissioned.
  2. To prevent accidental damage and puncture from falling objects, conventional roofs at elevations lower than those designed for human occupancy should include a protective wearing course or, in the alternative, should be designed as a Protected Membrane Roof system.
  3. Where membranes installed on vertical surfaces may be damaged from foot traffic or shifting coverings, they must be protected as, for example, with base metal flashings. See 13.3.5 Cap, Counter and Base Flashings.
  4. Filter fabrics are required for roof platforms supporting
    1. growing media and vegetation.
    2. sand and other fine materials.
    3. gravel with a diameter less than 12.7 mm (1/2”).
    4. wet mortar or concrete.
    5. XPS insulation above the membrane, in order to contain the insulation and thereby prevent ‘insulation stacking’ (displacement) when insulation boards become buoyant in water, and to prevent fines from settling at the membrane level and filling the voids between insulation board joints.
4. Drainage:
  1. Roofs designed as platforms to support roof coverings, amenity spaces or equipment must promote unimpeded drainage of storm or irrigation water. Where a roof covering material naturally drains (gravel, for example), no additional drainage design is required. In all other cases, the design must incorporate a drainage plane above the supporting roof platform.
  2. Overburden must be contained with drain guards, rigid barriers and filter fabric. See also 11.2.2 Roof Drains and Scuppers.
  3. Equipment supports placed on the roof system must not impede the flow of water to drains. To facilitate the adequate movement of water when supports are oriented perpendicular to drainage flow,
    1. utilize shorter supports, to a maximum length of 1200 mm (4’).
    2. incorporate drainage mats beneath the supports longer than 1200 mm (4’) in any direction.
5. Clearance and accessibility: equipment installed on structural supports or on top of the roof system must be spaced or located in order to promote access to drains, ease of maintenance and worker or occupant safety.
6. Integrity Scan: An Integrity Scan, performed by an RGC-recognized service provider to ensure the waterproofing is leak and damage-free, is required on all Waterproofing roof and grade-level Projects when overburden, amenities or equipment are or will be installed on the completed Waterproofing Assembly by
  1. anyone other than the Contractor.
  2. the Contractor, and the overburden, amenities or equipment exceed 150 mm (6”) in depth.
  An Integrity Scan is not required when the Contractor installs overburden, amenities or equipment equal to or less than 150 mm (6”) in depth.
7. Electronic Leak Detection (ELD) is optional, depending upon the roof design, building exposure and desired Guarantee coverage. See 1.3.4 Waterpoofing Integrity Scans and Electronic Leak Detection. See also 1.6 RoofStar Guarantee: Coverage and Limitations.

1.2.2 Roof Coverings

1.2.2.1 Gravel

Note that gravel used as ballast on a PMRA or MPMRA is considered a means of securement and is covered in 3 SECURING the ROOF ASSEMBLY and in 12.1 Protected and Modified Protected Membrane Assemblies.

When gravel is specified as the roof covering,
1. only washed gravel may be used.
When the gravel used as a roof covering is crushed, or is smaller than 12 mm (1/2”),
1. a geotextile protection layer must be installed immediately above the roof membrane.
2. the gravel must be deep enough to retain the geotextile protection layer.

1.2.2.2 Wearing Surfaces and Living Spaces

Any wearing surface may be installed on a conventionally insulated roof assembly, provided
1. the compressive strength of the insulation will support it.
2. the insulation in the roof assembly is overlaid with a suitable insulation overlay (see 8.3.1.2 (4)).
3. the wearing surface does not bond with or touch the roof field membrane or membrane flashing.
4. drainage of storm or irrigation water is not impeded.
When concrete paver walkways or platforms are specified, they must promote free drainage of water. This can be achieved by using adequately spaced
1. pedestals. vproprietary pads.
2. XPS insulation.
3. drainage mats.
Wearing surfaces may be sloped or level, depending upon the intent of the design, and therefore Project specifications and drawings should indicate this.
When cast-in-place concrete is used as a roof covering directly over the roof membrane, the concrete must be separated from the membrane with both of the following:
1. A bond-breaking material, such as a proprietary drainage mat or XPS insulation.
2. A filter fabric or barrier material acceptable to the membrane manufacturer, able to prevent the concrete slurry from reaching the membrane.

1.2.2.3 Vegetated Roof Systems (VRSs)

Modular vegetated systems must be designed for wind uplift resistance, based on the Specified Wind Loads calculated using the WIND-MVRA online calculator (see also 3 SECURING the ROOF ASSEMBLY). Since VRSs often provide ballast for PMRAs and may be installed by someone other than the roofing contractor, the Design Authority must specify the coordination of work to ensure the roof assembly is immediately and properly secured.
Conventionally insulated roof assemblies may be used to support any type of Vegetated Roof System (VRS), provided
1. the compressive strength of the insulation will support it.
2. the insulation in the roof assembly is overlaid with a suitable insulation overlay (see 8.3.1.2 (4)).
3. the membrane manufacturer is agreeable to the application and is confident the membrane can withstand the anticipated hydrostatic pressures when the vegetated system is fully saturated with water
4. the membrane is fully adhered.
Notwithstanding the above, semi-intensive and intensive vegetated systems should be designed as part of a Protected Membrane Roof Assembly. See also 14.1.2.1 (4) above.
Every roof that supports a Vegetated Roof System must have, in addition to a drainage layer and membrane protection, a
1. root barrier.
2. filter fabric layer.
Vegetated Roof Systems that are built in place should be designed with an additional layer of protection immediately below the growing media and above the rest of the roof and vegetation assembly, to ensure the protection of these materials from tools.
Separation Zones, which are free of growing media or vegetation and protect vulnerable membrane seams from root damage, must be
1. at least 300 mm (12”) wide, or greater as determined through Specified Wind Load calculations (see also 3 SECURING the ROOF ASSEMBLY).
2. bordered by a non-penetrating, surface-installed physical barrier (for example, a retention Tee).
3. installed around the perimeter of the Vegetated Roof System, and around any of the following, which may be contained within the area covered by the VRS:
  1. roof drains.
  2. roof penetrations.
  3. sleepers and curbs.
  4. any mechanical equipment not supported by a curb.
  5. expansion or control joints.
Membrane flashing must be protected from damage, both during the installation of vegetated systems and during ongoing maintenance. Refer to 13 METAL FLASHINGS for guidance.

1.2.3 Structures and Equipment

Refer to the general design standards and guidelines in 14.1.2.1 General.
Non-structural installations
1. are strongly recommended whenever practical, since they
  1. minimize the number of penetrations, curbs or sleepers necessary for structural securement.
  2. eliminate possible weak points in the membrane assembly, where a leak may occur.
  3. avoid dedicated mechanical drainage.
  4. simplify removal of materials when membrane repairs are required.
2. must be placed on an appropriate protection layer or supported by pedestals, pavers or other means of distributing weight and point loading.
3. may be placed on a Conventionally Insulated Roof provided the insulation in the roof assembly is capable of supporting all anticipated dead loads, live loads and point loads (see 14.1.2.1 (1)).
A structural concrete planter or water feature that is
1. cast-in-place should be constructed on a pre‐curb that is continuously waterproofed as part of the primary roof membrane and waterproofed independently of the primary roof membrane.
2. pre-cast must be secured to
  1. a pre‐curb that is continuously waterproofed as part of the primary roof membrane.
  2. structural supports that are waterproofed in keeping with the Standards in 11 PENETRATIONS and DRAINS.
When concrete walls or structures are constructed without a pre-curb, all concrete surfaces must be fully and continuously enveloped with the primary roof membrane. See also 1.6 (8).
Pre‐curbs must be
1. at least 100 mm (4") in height above the water plane of the highest adjacent roof assembly.
2. completely enveloped with fully adhered acceptable membrane flashing (including all faces of drainage knock‐outs).
3. properly waterproofed around dowels in their final position with either of the following:
  1. a 2-component catalyzed polymethyl methacrylate (PMMA) reinforced liquid membrane flashing system.
  2. two cured coats of an Accepted polyurethane or silicon-based single-component liquid flashing system. See 11.3.3.1 General for application standards.
When a structural planter adjoins a Protected Membrane Roof Assembly, the planter design must include either of the following options for drainage:
1. a plumbed mechanical drain that
  1. incorporates a debris guard and maintenance access.
  2. extends above the top surface of the growing media at least 50 mm (2”).
2. drainage knock-outs in the pre-curb wall, which should be wide enough to allow for the free flow of water over or past of the membrane flashing plies.
When a structural planter adjoins a conventionally insulated roof assembly, only a plumbed mechanical drain is permissible.
A design review is advisable when a structural water features incorporates penetrations for wiring, lights or other submerged features.
Tiles or other architectural finishes may be applied to the waterproofing membrane, subject to a written Variance from the RoofStar Guarantee administration and approval by the membrane manufacturer.
Drains, re-circulation inlets and outlets used in water features must include clamping rings and must be sealed to the membrane assembly.
When a leak detection system is specified, or required, only non‐ferrous metal drains may be used.
Drain connections to internal piping must be made with mechanical compression type seals only.

2 Materials

2.1 Membranes

Refer to the table in 9.2.1 for minimum membrane thickness and puncture resistance requirements.

2.2 Membrane Protection

Membranes must be protected by using one of the following materials directly above the roof membrane:
1. drainage mat.
2. asphaltic core board measuring at least 3 mm (1/8”) thick.
3. XPS insulation measuring at least 25 mm (1”) thick.
4. a geotextile protection layer with a minimum thickness/weight of 200 g/m2 (used in VRS applications, where decorative gravel is crushed or smaller than 12 mm (1/2”) in diameter, or where the roof covering, superimposed structure or equipment does not exceed the load-bearing capacity of the protection material).

2.3 Insulation and Insulation Overlays

2.4 Components for Vegetated Systems and Other Roof Coverings

While drainage mats, filter fabrics, root barriers and other vegetated system components are ancillary to the roof assembly, they nevertheless must be
1. acceptable to the manufacturer of the primary membrane and XPS insulation (when used).
2. suitable for the installed roof covering.
3. selected for their ability to support dead loads, live loads and point loads.
4. capable of permitting the anticipated flow rate of water.
Geosynthetic drainage cores, and geocomposites with factory-laminated filter fabrics, must
1. be molded (dimpled) or woven plastic grids so that it contacts no more than 40% of XPS insulation surface area.
2. be manufactured with a minimum thickness of 9.5 mm (3/8”).
3. provide a uniform support for roof coverings, structures or equipment installed on the roof platform.
4. have a compressive strength equal to or greater than the design and anticipated live loads of the roof platform and its supported coverings, structures or equipment.
Fabric filter mats must be
1. water permeable and have proven long term weather resistance.
2. strong enough to withstand traffic abuse and prevent displacement of insulation boards under flotation conditions.
Root intrusion barriers
1. must be sheets or boards that are acceptable to the primary roof membrane manufacturer.
2. may be polyethylene or polypropylene sheeting, provided the material is no less than .2mm (8 mils) thick.
Membrane protection must be either of the following materials:
1. asphaltic core board measuring at least 3 mm (1/8”) thick.
2. XPS insulation measuring at least 25 mm (1”) thick.
3. a geotextile protection layer with a minimum thickness/weight of 200 g/m2 (applicable when the gravel is crushed or smaller than 12 mm (1/2”) in diameter).
Moisture retention and reservoir layers must be acceptable to the manufacturer/supplier of the vegetated system.

2.5 Decorative Gravel

Decorative gravel (different in function from gravel ballast) must be washed and may be smooth or crushed.
Large grade gravel may withstand wind scour more effectively than smaller gravel. The Design Authority should determine the gradients, based on the Specified Wind Loads for the roof. For size options, see 12.1.2 (6) for Protected Membrane Roof Assemblies.

2.6 Pavers and Pedestals

Pavers that are partially supported (i.e. with pedestals) should be capable of resisting anticipated loads (consider, for example, hydraulically pressed concrete pavers).
Pedestals
1. should be adjustable, when a level surface is required.
2. must be proprietary (purpose-made) and include an integral spacer rib measuring at least a 3mm (⅛”), to uniformly separate pavers.

3 Application

3.1 General

3.1.1 Membranes

Membranes and membrane flashing must be installed in keeping with the Standards found elsewhere in this Manual.
Protection of roof membranes from mechanical damage caused by tools, accident or the work of others is mandatory during the installation and maintenance of any roof covering or living space.

3.1.2 Drainage

A drainage mat must be installed below the XPS insulation. A second drainage layer may be installed above the insulation but this is at the discretion of the Design Authority.
Specialized proprietary drainage products must be acceptable to the membrane manufacturer.

3.1.3 Filter Fabric

Fabric filter mats must be
1. installed loose-laid (un-bonded) over the insulation and below any type of ballast or roof covering.
2. overlapped at all edges a minimum of 300mm (12").
3. at least 2.5 m x 2.5 m (8’ x 8’) in size.
4. slit to fit over roof penetrations, and cut out around roof drains and other openings.
Filter fabric must extend up perimeter edges and curbs, and must be placed loose (unattached) under metal counter flashings or wall finishes. See also 13.3.5 Cap, Counter and Base Flashings concerning metal flashings.

3.2 Roof Coverings

3.2.1 Decorative Gravel

When gravel is specified as a roof covering, only washed gravel may be used.
Ballast guards must be installed around all roof drains. See 11.2.2 Roof Drains & Scuppers.
Crushed gravel specified as a roof covering must be installed over a geotextile protection layer, or its equivalent, when the gravel is crushed or smaller than 12 mm (1/2”) in diameter.

3.2.2 Wearing Surfaces and Living Spaces

Pavers and unit-type masonry, such as brick or stone, must be supported by
1. proprietary (purpose-made) pedestals with at least a 3mm (⅛”) integral spacer ribs for uniform spacing of pavers.
2. a proprietary drainage layer overlaid with a filter fabric mat.
3. a drainage layer of loose aggregate (such as pea gravel) measuring at least 25 mm (1") in depth, installed over a filter fabric.
Pedestals or a drainage layer must permit at least 12.7 mm (½″) of vertical separation between the paver and the underlying substrate, to provide airflow for drying surfaces and assist in leveling. Pedestals should not impede the flow of water or air, and should uniformly distribute the dead load of pavers, and other unit masonry products, as well as predicted live loads.

3.2.3 Vegetated Roof Systems

All vegetated roof systems must be installed as specified and shown on drawings, and in any case must include a
1. root barrier.
2. drainage layer.
3. filter cloth.
Roofs that support built-in-place soil or growing media beds should include an additional penetration-resistant protection course between the growing bed and other vegetated assembly materials. The protection course prevents damage to these materials whenever sharp-pointed or edged tools are used for the maintenance of the vegetated assembly.
Root intrusion barriers must be
1. installed in a continuous plane above the roof membrane.
2. located within the vegetated system as specified by the Design Authority.
3. sealed at all seams and laps with a compatible tape, as directed by the manufacturer's instructions.
4. carried up the inside of soil retention perimeters (separation zones).
5. sealed to the separation zone edge material.
Separation Zones must be
1. at least 300 mm (12”) wide.
2. bordered by a non-penetrating, surface-installed physical barrier.
3. installed along all roof perimeters.
4. installed around
  1. up-stands.
  2. roof drains.
  3. penetrations.
  4. sleepers and curbs. mechanical equipment.
  5. expansion or control joints.

3.3 Structures and Equipment

Structural planters and water features (pools, ponds, water courses) must be constructed with a pre‐curb (start‐up curb), onto which the planter or water feature wall is formed and poured.
Pre‐curbs must be
1. at least 100 mm (4") in height above the water plane of the highest adjacent roof assembly.
2. completely enveloped with fully adhered acceptable membrane flashing (including all faces of drainage knock‐outs).
Dowels (reinforcement bar) must be
1. inserted into the pre‐curb after application of the membrane flashing.
2. waterproofed in their final position, where they penetrate the pre-curb, using either a reinforced 2-part liquid membrane flashing or two (2) applications of a single-component liquid membrane flashing (fully cured between coats),
  1. applied to properly prepared surfaces.
  2. in keeping with the application standards in 11.3.3.3 Liquid Membrane Flashing for 2-part reinforced liquid membrane flashing, or the manufacturer’s instructions for single-component liquid membrane flashing.
  3. applied no less than 50 mm (2”) on vertical surfaces and in a radius around the base of each dowel.
Structural planters and water features must be waterproofed on the inside with a fully‐adhered membrane that terminates on the inside vertical surface of the planter at least 100 mm (4”) above the level of soil, growing medium or water, or at the outside edge of the top surface of the planter or water feature wall.
Membranes must be terminated in keeping with the Standards in 11 DRAINS and PENETRATIONS, and protected with metal reglet or cap flashings in keeping with 13 METAL FLASHINGS.
A membrane integrity scan and any resulting repairs must be undertaken before the membrane is covered or submerged.