OBC DIVISION B · PART 9 — HOUSING AND SMALL BUILDINGSUpdated for the 2024 Ontario Building Code
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Section 9.13 — Dampproofing, Waterproofing and
Full text of Section 9.13 (Dampproofing, Waterproofing and) — Division B, Part 9 (Housing and Small Buildings) of the 2024 Ontario Building Code, with every article reproduced below.
On this page:
9.13.1.1.9.13.2.1.9.13.2.2.9.13.2.3.9.13.2.4.9.13.2.5.9.13.2.6.9.13.2.7.9.13.3.1.9.13.3.2.9.13.3.3.9.13.3.4.9.13.3.5.9.13.4.1.9.13.4.2.9.13.4.3.
9.13.1.1.9.13.2.1.9.13.2.2.9.13.2.3.9.13.2.4.9.13.2.5.9.13.2.6.9.13.2.7.9.13.3.1.9.13.3.2.9.13.3.3.9.13.3.4.9.13.3.5.9.13.4.1.9.13.4.2.9.13.4.3.
9.13.1.General
9.13.1.1.Scope and Application permalink →
(1) This Section presents measures to control the ingress of water, moisture and soil gas.
(2) Subsection 9.13.2. applies to below-ground walls and floors-on-ground where drainage is provided in accordance
with Section 9.14. over and along the entire below-ground portion of the foundation wall.
(3) Subsection 9.13.3. applies to below-ground walls, floors-on-ground and roofs of underground structures that are
subject to hydrostatic pressure.
(4) Subsection 9.13.4. applies to walls, roofs and floors that are in contact with the ground.
9.13.2.Dampproofing
9.13.2.1.Required Dampproofing permalink →
(1) Except as provided in Sentence (4) and Article 9.13.3.1., where the exterior finished ground level is at a higher
elevation than the ground level inside the foundation walls, exterior surfaces of foundation walls below ground level shall
be dampproofed.
(2) Except as provided in Sentence (3) and Article 9.13.3.1., floors-on-ground shall be dampproofed.
(3) Floors in garages, floors in unenclosed portions of buildings and floors installed over granular fill in conformance
with Article 9.16.2.1. need not be dampproofed.
(4) Dampproofing in Sentence (1) is not required where the exterior surfaces of foundation walls below ground level are
waterproofed.
9.13.2.2.Dampproofing Materials permalink →
(1) Materials installed to provide required dampproofing shall be
(a) capable of protecting assemblies against moisture transfer from the ground,
(b) compatible with adjoining materials, and
(c) resistant to mechanisms of deterioration that may reasonably be expected, given the nature, function and exposure of
the materials.
(2) Except as otherwise specified in this Section, materials used for exterior dampproofing shall
(a) conform to one of the following standards:
(i) ASTM D1227 / D1227M, “Standard Specification for Emulsified Asphalt Used as a Protective Coating for
Roofing,” Type III, Class I,
(ii) ASTM D4479 / D4479M, “Asphalt Roof Coatings - Asbestos-Free,” Type III,
(iii) CAN/CGSB-51.34-M, "Vapour Barrier, Polyethylene Sheet for Use in Building Construction," or
(iv) CAN/CSA-A123.4, "Asphalt for Constructing Built-Up Roof Coverings and Waterproofing Systems," or
(b) have a water vapour permeance of not more than 43 ng/(Pa×s×m 2) when tested in accordance with Procedure A (wet
cup) of ASTM E96 / E96M, “Standard Test Methods for Water Vapor Transmission of Materials,” and consist of
one of the following material types:
(i) a vapour-resistant coating,
(ii) a cold-fluid-applied or hot-rubberized bituminous dampproofing membrane,
(iii) a liquid-applied or spray-applied asphalt-based emulsion dampproofing, or
(iv) a Type III hot-applied asphalt.
9.13.2.3.Preparation of Surface permalink →
(1) The area in which dampproofing is to be carried out shall be kept free of water during the application and curing of
the dampproofing system.
(2) The surface to be dampproofed shall be prepared in accordance with the instructions of the dampproofing material
manufacturer.
(3) Where the dampproofing material is to be applied on insulating concrete form (ICF) walls, the instructions of the
ICF wall manufacturer shall be followed.
(4) Unit masonry walls to be dampproofed shall be parged on the exterior face below ground level with not less than
6 mm of mortar conforming to Section 9.20. coved over the footing.
(5) Concrete walls to be dampproofed shall have holes and recesses sealed with cement mortar or a mastic or sealant
that is suitable for vertical applications and compatible with the dampproofing material.
(6) The surface required to be dampproofed shall be clean and dry and free of ice, snow, frost, dust, dirt, oil, grease,
cracks, projections, depressions, loose particles and debris that could be detrimental to the performance of the membrane
to be applied.
9.13.2.4.Application of Dampproofing Material permalink →
(1) Exterior dampproofing shall be applied from finished ground level to the top of the exterior of the footing.
(2) Unless otherwise stated in this Subsection, dampproofing shall be installed in accordance with the manufacturer’s
instructions with regard to
(a) surface priming,
(b) conditions during application,
(c) application quantity and rate, and
(d) curing times.
(3) Joints, cracks and penetrations shall be sealed to maintain the continuity of the dampproofing, where the
dampproofing material is not capable of bridging such discontinuities.
9.13.2.5.Moisture Protection for Interior Finishes (See Note A-9.13.2.5.) permalink →
(1) The interior surface of foundation walls below ground level shall be protected by means that minimize the ingress of
moisture from the foundation wall into interior spaces, where
(a) a separate interior finish is applied to a concrete or unit masonry wall that is in contact with the soil, or
(b) wood members are placed in contact with such walls for the installation of insulation or finish.
(2) Except as provided in Sentence (3), where the protection of interior finishes required in Sentence (1) consists of
membranes or coatings,
(a) the membrane or coating shall extend from the basement floor surface up to the highest extent of the interior
insulation or finish, but not higher than the exterior finished ground level, and
(b) no membrane or coating with a permeance less than 170 ng/(Pa×s×m2) shall be applied to the interior surface of the
foundation wall above ground level between the insulation and the foundation wall.
(3) Where insulation functions as both moisture protection for interior finishes and as a vapour barrier in accordance
with Subsection 9.25.4., it shall be applied over the entire interior surface of the foundation wall.
9.13.2.6.Dampproofing of Floors-on-Ground permalink →
(1) Where dampproofing is installed below the floor, it shall consist of
(a) polyethylene not less than 0.15 mm thick with joints lapped not less than 100 mm,
(b) Type S roll roofing with joints lapped not less than 100 mm, or
(c) rigid extruded/expanded polystyrene with sealed or shiplapped joints that has
(i) sufficient compressive strength to support the floor assembly, and
(ii) a water vapour permeance complying with Clause 9.13.2.2.(2)(a).
(See Note A-9.13.2.6.(1))
(2) Where dampproofing is installed between a floor-on-ground and a finished floor, it shall consist of
(a) rigid extruded/expanded polystyrene with sealed or shiplapped joints that has
(i) sufficient compressive strength to support the floor assembly, and
(ii) a water vapour permeance complying with Clause 9.13.2.2.(2)(b), or
(b) polyethylene not less than 0.05 mm thick with joints lapped not less than 100 mm.
9.13.2.7.Dampproofing of Preserved Wood Foundation Walls permalink →
(1) Preserved wood foundation walls shall be dampproofed as described in CSA S406, “Specification of permanent
wood foundations for housing and small buildings.”
9.13.3.Waterproofing
9.13.3.1.Required Waterproofing permalink →
(1) Where hydrostatic pressure occurs, waterproofing is required for assemblies separating interior space from the
ground to prevent the ingress of water into building assemblies and interior spaces.
(2) Waterproofing is required for roofs of underground structures to prevent the ingress of water into building
assemblies and interior spaces.
9.13.3.2.Waterproofing Materials permalink →
(1) Materials installed to provide required waterproofing shall be
(a) compatible with adjoining materials, and
(b) resistant to mechanisms of deterioration that may reasonably be expected, given the nature, function and exposure of
the materials.
(2) Materials used for exterior waterproofing shall conform to
(a) ASTM D1227 / D1227M, “Standard Specification for Emulsified Asphalt Used as a Protective Coating for
Roofing,” in which case, they shall be installed in accordance with Sentence 9.13.3.3.(3),
(b) ASTM D3019 / D3019M, “Standard Specification for Lap Cement Used with Asphalt Roll Roofing, Non-Fibered,
and Fibered,” where non-fibered and non-asbestos-fibered (Types I and III) asphalt roll roofing are permitted,
(c) ASTM D4479 / D4479M, “Standard Specification for Asphalt Roof Coatings - Asbestos-Free,” in which case, they
shall be installed in accordance with Sentence 9.13.3.3.(3) and with reinforcing material,
(d) ASTM D4637 / D4637M, “Standard Specification for EPDM Sheet Used In Single-Ply Roof Membrane,”
(e) ASTM D4811 / D4811M, “Standard Specification for Nonvulcanized (Uncured) Rubber Sheet Used as Roof
Flashing,”
(f) ASTM D6878 / D6878M, “Standard Specification for Thermoplastic Polyolefin Based Sheet Roofing,”
(g) CGSB 37-GP-9Ma, “Primer, Asphalt, Unfilled, for Asphalt Roofing, Dampproofing and Waterproofing,” where a
primer is required,
(h) CAN/CGSB-37.50-M, “Hot-Applied, Rubberized Asphalt for Roofing and Waterproofing,”
(i) CAN/CGSB-37.54, “Polyvinyl Chloride Roofing and Waterproofing Membrane,”
(j) CGSB 37-GP-56M, “Membrane, Modified, Bituminous, Prefabricated, and Reinforced for Roofing”,
(k) CAN/CGSB-37.58-M, “Membrane, Elastomeric, Cold-Applied Liquid, for Non-Exposed Use in Roofing and
Waterproofing,”
(l) CAN/CSA-A123.2, “Asphalt-Coated Roofing Sheets,”
(m) CAN/CSA-A123.4, “Asphalt for Constructing Built-Up Roof Coverings and Waterproofing Systems,” in which
case, they shall be installed with reinforcing material, or
(n) CSA A123.17, “Asphalt Glass Felt Used in Roofing and Waterproofing.”
9.13.3.3.Preparation of Surface permalink →
(1) Surfaces to be waterproofed shall be prepared in accordance with the instructions of the waterproofing material
manufacturer.
(2) Where the waterproofing material is to be applied on ICF walls, the instructions of the ICF wall manufacturer shall
be followed.
(3) Unit masonry walls that are to be waterproofed shall be parged on exterior surfaces below ground level with not less
than 6 mm of mortar conforming to Section 9.20. coved over the footing.
(4) Concrete walls that are to be waterproofed shall have all holes and recesses sealed with mortar or waterproofing
material.
(5) Surfaces required to be waterproofed shall be clean and dry and free of ice, snow, frost, dust, dirt, oil, grease, cracks,
projections and depressions, loose particles and debris that could be detrimental to the performance of the waterproofing
material.
9.13.3.4.Application of Waterproofing Membranes permalink →
(1) Unless otherwise stated in this Subsection, waterproofing shall be installed in accordance with the manufacturer’s
instructions with regard to
(a) surface priming,
(b) conditions during application,
(c) the required number of layers of reinforcing fabric on foundations, footings, floors, walls and structural slabs,
(d) application quantity and rate, and
(e) curing times.
(2) Waterproofing shall be continuous across joints and at junctions between different building elements.
(3) The waterproofed surface shall be protected with a suitable material to minimize mechanical damage during
backfilling.
(4) The area in which the waterproofing is to be carried out shall be kept free of water during the application and curing
of the waterproofing system.
9.13.3.5.Floor Waterproofing System permalink →
(1) Basement floors-on-ground to be waterproofed shall have a system of membrane waterproofing provided between
2 layers of concrete, each of which shall be not less than 75 mm thick, with the floor membrane made continuous with the
wall membrane to form a complete seal.
9.13.4.Soil Gas Control (See Note A-9.13.4.)
9.13.4.1.Application and Scope permalink →
(1) This Subsection applies to
(a) wall, roof and floor assemblies separating conditioned space from the ground, and
(b) the rough-in to allow the future protection of conditioned space that is separated from the ground by a wall, roof or
floor assembly.
(2) This Subsection addresses the leakage of soil gas from the ground into the building.
(3) In areas of the province where radon gases are known to be a problem, the building shall be designed and
constructed to meet the radon limitations in Article 9.1.1.7.
9.13.4.2.Protection from Soil Gas Ingress permalink →
r1 (1) Except as provided in Sentence (1.1), all wall, roof and floor assemblies in contact with the ground shall be
constructed to resist the leakage of soil gas from the ground into the building in accordance with Subsection 9.25.3. or
MMAH Supplementary Standard SB-9, “Requirements for Soil Gas Control.”
(1.1) Construction to resist leakage of soil gas into the building is not required for garages and unenclosed portions of
buildings.
(1.2) Where polyethylene is used to provide a barrier to soil gas ingress through floors-on-ground, it shall conform to
CAN/CGSB‑51.34‑M, “Vapour Barrier, Polyethylene Sheet, for Use in Building Construction.”
(2) Unless the space between the air barrier system and the ground is designed to be accessible for the future
installation of a subfloor depressurization system, dwelling units and buildings containing residential occupancies shall
be provided with the rough-in for a radon extraction system conforming to Article 9.13.4.3.
(3) Where buildings are used for occupancies other than those described in Sentence (2), protection from radon ingress
and the means to address high radon concentrations in the future shall conform to
(a) Article 9.13.4.3., or
(b) Parts 5 and 6. (See Article 5.4.1.1. and 6.2.1.1.)
(See Note A-9.13.4.2.(3))
9.13.4.3.Providing for the Rough-in for a Subfloor Depressurization System permalink →
(See Note A-9.13.4.3.)
(1) Floors-on-ground shall be provided with a rough-in for subfloor depressurization consisting of
(a) a gas-permeable layer, an inlet and an outlet as described in Sentence (2), or
(b) clean granular material and a pipe as described in Sentence (3).
(2) The rough-in referred to in Clause (1)(a) shall include
(a) a gas-permeable layer installed in the space between the air barrier and the ground to allow the depressurization of
that space,
(b) an inlet that allows for the effective depressurization of the gas-permeable layer, and (See Note A-9.13.4.3.(2)(b) and
(3)(b)(i))
(c) an outlet in the conditioned space that
(i) permits connection to depressurization equipment,
(ii) is sealed to maintain the integrity of the air barrier system, and
(iii) is clearly labeled to indicate that it is intended only for the removal of radon from below the floor-on-ground.
(3) The rough-in referred to in Clause (1)(b) shall include
(a) clean granular material installed below the floor-on-ground in accordance with Sentence 9.16.2.1.(1), and
(b) pipe not less than 100 mm in diameter installed through the floor, such that
(i) its bottom end opens into the granular layer required in Clause (a) at or near the centre of the floor and not
less than 100 mm of granular material projects beyond the terminus of the pipe measured along its axis, (See
Note A-9.13.4.3.(2)(b) and (3)(b)(i))
(ii) its top end permits connection to depressurization equipment and is provided with an airtight cap, and
(iii) the pipe is clearly labeled near the cap and, if applicable, every 1.8 m and at every change in direction to
indicate that it is intended only for the removal of radon from below the floor-on-ground.
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Code text is reproduced for reference from the Ontario Building Code (O. Reg. 163/24, 2024 Building Code Compendium). This page is provided for general information and is not an official copy. Always verify requirements against the official Ontario Building Code and confirm with your local building department.