Resources

7 Sources of Basement Moisture 

Moisture develops in various ways within basements and other below ground structures. Critically all of these sources can contribute to a space being deemed unsuitable as a habitable space, can also cause extensive damage to personal possessions, while also increasing the risks to the health and safety of you and your family.

GROUND WATER

Water that comes from within the ground/earth and includes surface water percolating through the strata as it makes its way down to the water table. Building at or near the water table can create persistent damp conditions, with careful waterproofing design and membrane selection critical in reducing risk of failure.

SURFACE WATER

Surface water is water that has not yet penetrated ground.
Adequate surface drainage and profiling will reduce the volume of water that penetrates porous ground and thereby reducing the hydraulic load against a basement structure, but particularly where ingress into an internal space has occurred then this may not be acceptable as a long-term solution in itself.

RISING DAMP

Rising damp occurs when ground water ‘wicks’ via capillary action up through porous masonry or moisture sensitive materials that are in contact with the ground.
This can occur even when when no direct contact with free-water exists, and no hydraulic load or ‘head’ of pressure is present.
This can be the result of a compromised damp proof course (DPC).

MOISTURE VAPOUR TRANSMISSION

Moisture vapour is water in its gaseous state, and moisture vapour transmisson is the transfer of moisture vapour through a substrate, membrane or material.
Waterproofing membranes will stop a droplet of water passing through, but have varying rates of moisture vapour transmission, the rate of which is a defining difference between a waterproofing membrane and ‘paint’.

CONDENSATION

Condensation is not necessarily a source of water but the result of the conversion of moisture from its gaseous to liquid form.
Atmospheric changes such as an increase in humidity and/or a drop in temperature will result in the formation of condensation on surfaces at or near the dew point, and lead to the formation of mould.

INTERSTITIAL CONDENSATION

Interstitial condensation is the formation of condensation between layers of a building or membrane, and occurs where there is differential moisture vapour transmission rates of the layers, resulting in moisture being trapped, In basements this can occur between external structural walls and internal plaster linings, which is a key focus of NCC Vol2 3.8.7.2 (b)

GENERAL OCCUPANCY

General occupancy and use of a below ground area can generate moisture which can be trapped within the space, particularly where there is inadequate ventilation or atmospheric controls.
The use of unvented dryers, washing, cooking, cleaning and even perspiration, can be significant contributors to atmospheric moisture content, leading to mould and mildew.

6 Types of Basement Structures 

Educate yourself on what type of basement exists within your home, and pre-determine what the intended end use of the area will be. This provides important information for our technicians, while guiding a suitable design and specification for our fully guaranteed waterproofing systems.

BASEMENT

A basement is defined as an area that is one or more floors of a building that is either partly or completely below the ground floor.

SUB-BASEMENT

A sub-basement is another level of basement below the first level. Commercial building car parks are a typical example of basement and sub-basement construction, and is also referred to as ‘deep basement’

DAYLIGHT BASEMENT

A daylight basement is where at least part of the entire basement construction is above the external ground level, to provide reasonably sized windows on at least one side. This would also include basements with ‘light wells’.

WALK OUT BASEMENT

A below external ground level area that can be accessed from the ground level on at least one side. Most commonly referred to as ‘Terraced Construction’ or a building constructed on a sloping or’ cut and fill’ block, and is one of the most common designs in Australian residential properties.

CELLAR

Defined as an underground room that is used for the storage of wine (or coal in years gone by), and is constructed with the purpose to remain ‘cool’ all year, with the items stored not subject to moisture damage. Cellars originally had earth floors, however this has changed to concrete over the years.

CRAWL SPACE

Crawl spaces provide access to pipes, sub structures and other services which may otherwise be difficult to access. You generally cannot stand up in a ‘crawl space’.

3 Grades of Basement Waterproofing Systems 

Let’s take a closer look at the intended use of your basement or below ground space and how that determines the required grade of waterproofing. The reality is most homeowners want to optimise functionality, meaning a Grade 3 habitable space is the desired result.

GRADE 1

Some seepage and damp areas tolerable
Non-Habitable Space

EXAMPLES
– Commercial basement
– Car parking
– Areas where there will be no finishes or linings on the walls.

GRADE 2

No water penetration acceptable. Damp areas tolerable
Non-Habitable Space

EXAMPLES
– Basement plant and equipment rooms.
– Lift pits, pump rooms, storage rooms.
– Areas where there will be no finishes or linings on the walls.

GRADE 3

No water penetration or moisture acceptable
Habitable Space

EXAMPLES
– Basement media room
– Home gym
– Leisure or entertainment space
– Areas where there will be moisture sensitive materials on the inside, such as plasterboard linings.

3 Types of Waterproofing Systems

Dryspace Solutions utilises the global British Standard to guide systems implementation, meaning the most appropriate ‘for use’ classification into one of these three types

The British Standard grades basements and other below ground structures based on their intended use, which then determines the level of waterproofing protection required. Dryspace Solutions classifies waterproofing membranes based on the types detailed in BS8102:2009.

There are many different ways in which a property can be designed and waterproofed to achieve the required Grade, 1, 2 or 3, but all waterproofing systems can be classified into one of these three types:

Type A – represents systems that are ‘applied’ to a substrate, either internally, externally or sandwiched.
Type B – represents ‘built-in’ systems i.e. the water resistance is built into the structure and would typically include concrete additives and waterstops at joints and junctions.
Type C – represents ‘cavity drain’ systems, which are installed to the internal side of a structure, and more accurately described as a ‘moisture and water management’ system.

TYPE A

Protection against water ingress by a barrier membrane applied to the structure. This can be applied both internally or externally.

TYPE B

‘Structurally integral’ joint seals, concrete additives, injectable grouts and epoxies, and maintainable inter joint protection against water transmission.

TYPE C

An internally maintainable, drained system with dedicated ground water discharge management. Suitable for the management of condensation and water vapour.

Type A Basement Waterproofing Systems

What is Type A Waterproofing? How and where should it be used in my basement waterproofing project?

Defined in the BS8102:2009 as a ‘barrier membrane’, Type A waterproofing systems are those which are applied to either the internal or external substrate of the basement structure, to prevent the ingress of water. These barrier membranes also fulfil the requirements of the Building Code of Australia Part 2.2 Damp and Weatherproofing.

Examples of these membranes are bentonite to the underslab and walls, bitumen liquid or sheet membranes, cementitious coatings to the walls or polymer based liquids.

Type A systems can be used for both new construction and remediation works and are typically applied:

• Under the slab
• To the external basement walls
• To the top (positive side) or the podium slab
• To the internal walls of the basement structure (usually installed when there’s zero boundary or negative hydrostatic pressure).

Type A Waterproofing Case Study

Boutique Medium Rise Apartment Building – Anglers Esplanade, Runaway Bay

Dryspace Solutions was contracted to undertake the waterproofing of this luxury apartment complex before
construction commenced. Works included the design and installation of waterproofing systems to the entire building, including the basement, bathrooms, balconies and roof decks.
For the basement works we specified and installed the following elements:

• Underslab bentonite sheet membrane
• External wall bentonite sheet membrane
• Waterstops where required
• Detailing and sealing of pipe penetrations
• Application of waterproofing membrane to the podium slab level
• Application of a negative hydrostatic membrane to selected high risk walls on the internal basement walls

Type B Basement Waterproofing Systems

What is Type B Waterproofing? How and where should it be used in my basement waterproofing project?

Defined in the BS8102:2009 as an ‘integral protection’ – Type B waterproofing systems are those where the structure itself is integrally waterproof and the primary resistance against water ingress. These structures are generally made of high grade concrete with reinforcement fabric or additives, which will help reduce water ingress through cracks etc… in conjunction with water bars and water stops at joints and junctions.

Hydrophillic and hydrophobic grouts and epoxies, and other injectable sealants which are typically used for the remediation of water ingress through cracks are also considered Type B Waterproofing Systems as they become ‘integrally part of the structure’.

Type B systems are typically applied as:

• Additives to the concrete such as crystallines or cementitious powders
• Waterbars, waterstops and waterplugs
• Injectable grouts and epoxies

Type B Waterproofing Case Study

Multi-Level Luxury Beach House – Marine Parade, Miami QLD

This luxury beach house was designed with essentially a ‘zero boundary’ pile construction basement. To ensure the waterproofing of the basement several different waterproofing systems were installed, including bentonite sheeting, swellable water stops and concrete waterproof additives.

For the basement works we specified and installed the following elements:

• Underslab bentonite sheet membrane
• ‘Sandwiched’ bentonite sheet membrane
• Installation of waterstops where required
• Waterproofing Admix concrete additives to shotcrete and slabs
• Detailing all joints and junctions using

Type C Basement Waterproofing Systems

What is Type C Waterproofing? How and where should it be used in my basement waterproofing project?

A Type C system is defined as a below ground, maintainable waterproofing system, comprising of membranes, drainage and pumping systems where necessary.

As part of the BS8102:2009, it is considered ‘accepted’ that water has the potential to enter a building. The Type C membrane creates an internal cavity that allows the water to depressurise, subsequently allowing appropriate management of the water.

Once the water is collected it is then discharged from the property via natural stormwater or sump pump systems.

Type C systems are typically applied as:

• Internal below ground walls, floors and sometimes vaulted ceilings
• Above ground masonry walls where condensation and moisture ingress can be an issue
• Used in conjunction with both Type A and Type B systems to create a complete waterproofing solution

Type C Waterproofing Case Study

‘Palm Springs’ Luxury Residence, Sanctuary Cove, QLD

This custom built, luxury home was designed with a full habitable space basement which included a media room, gym and cellar. It was originally constructed with an external sheet waterproofing membrane which was compromised during the back-filling process, resulting in substantial water ingress into the basement, even during rain free periods.

Dryspace Solutions specified and installed a Type C, Cavity Drain membrane system to both the walls and the floors, draining into the two sump systems that were in place.

The cavity drain systems handle both the free water ingress, moisture vapour and condensation to produce a totally dry, internal habitable space.

7 Sources of Basement Moisture 

Moisture develops in various ways within basements and other below ground structures. Critically all of these sources can contribute to a space being deemed unsuitable as a habitable space, can also cause extensive damage to personal possessions, while also increasing the risks to the health and safety of you and your family.

GROUND WATER

Water that comes from within the ground/earth and includes surface water percolating through the strata as it makes its way down to the water table. Building at or near the water table can create persistent damp conditions, with careful waterproofing design and membrane selection critical in reducing risk of failure.

SURFACE WATER

Surface water is water that has not yet penetrated ground.
Adequate surface drainage and profiling will reduce the volume of water that penetrates porous ground and thereby reducing the hydraulic load against a basement structure, but particularly where ingress into an internal space has occurred then this may not be acceptable as a long-term solution in itself.

RISING DAMP

Rising damp occurs when ground water ‘wicks’ via capillary action up throughporous masonry or moisture sensitive materials that are in contact with theground.
This can occur even when when no direct contact with free-water exists,and no hydraulic load or ‘head;’ of pressure is present.
This can be the result of acompromised damp proof course (DPC).

MOISTURE VAPOUR TRANSMISSION

Moisture vapour is water in its gaseous state, and moisture vapour transmisson is the transfer of moisture vapour through a substrate, membrane or material.
Waterproofing membranes will stop a droplet of water passing through, but have varying rates of moisture vapour transmission, the rate of which is a defining difference between a waterproofing membrane and ‘paint’.

CONDENSATION

Condensation is not necessarily a source of water but the result of the conversion of moisture from its gaseous to liquid form.
Atmospheric changes such as an increase in humidity and/or a drop in temperature will result in the formation of condensation on surfaces at or near the dew point, and lead to the formation of mould.

INTERSTITIAL CONDENSATION

Interstitial condensation is the formation of condensation between layers of a building or membrane, and occurs where there is differential moisture vapour transmission rates of the layers, resulting in moisture being trapped, In basements this can occur between external structural walls and internal plaster linings, which is a key focus of NCC Vol2 3.8.7.2 (b)

GENERAL OCCUPANCY

General occupancy and use of a below ground area can generate moisture which can be trapped within the space, particularly where there is inadequate ventilation or atmospheric controls.
The use of unvented dryers, washing, cooking, cleaning and even perspiration, can be significant contributors to atmospheric moisture content, leading to mould and mildew.

6 Types of Basement Structures 

Educate yourself on what type of basement exists within your home, and pre-determine what the intended end use of the area will be. This provides important information for our technicians, while guiding a suitable design and specification for our fully guaranteed waterproofing systems.

BASEMENT

A basement is defined as an area that is one or more floors of a building that is either partly or completely below the ground floor.

SUB-BASEMENT

A sub-basement is another level of basement below the first level.Commercial building car parks are a typical example of basement and sub-basement construction, and is also referred to as ‘deep basement’

DAYLIGHT BASEMENT

A daylight basement is where at least part of the entire basement construction is above the external ground level, to provide reasonably sized windows on at least one side. This would also include basements with ‘light wells’.

WALK OUT BASEMENT

A below external ground level area that can be accessed from the ground level on at least one side. Most commonly referred to as ‘Terraced Construction’ or a building constructed on a sloping or’ cut and fill’ block, and is one of the most common designs in Australian residential properties.

CELLAR

Defined as an underground room that is used for the storage of wine (or coal in years gone by), and is constructed with the purpose to remain ‘cool’ all year, with the items stored not subject to moisture damage. Cellars originally had earth floors, however this has changed to concrete over the years.

CRAWL SPACE

Crawl spaces provide access to pipes, sub structures and other services which may otherwise be difficult to access. You generally cannot stand up in a ‘crawl space’.

3 Grades of Basement Waterproofing Systems 

Let’s take a closer look at the intended use of your basement or below ground space and how that determines the required grade of waterproofing. The reality is most homeowners want to optimise functionality, meaning a Grade 3 habitable space is the desired result.

GRADE 1

Some seepage and damp areas tolerable
Non-Habitable Space

EXAMPLES
– Commercial basement
– Car parking
– Areas where there will be no finishes or linings on the walls.
6 Signs Your Basement is Leaking

GRADE 2

No water penetration acceptable. Damp areas tolerable
Non-Habitable Space

EXAMPLES
– Basement plant and equipment rooms.
– Lift pits, pump rooms, storage rooms.
– Areas where there will be no finishes or linings on the walls.

GRADE 3

No water penetration or moisture acceptable
Habitable Space

EXAMPLES
– Basement media room
– Home gym
– Leisure or entertainment space
– Areas where there will be moisture sensitive materials on the inside, such as plasterboard linings.

3 Types of Waterproofing Systems

Dryspace Solutions utilises the global British Standard to guide systems implementation, meaning the most appropriate ‘for use’ classification into one of these three types

Type A Basement Waterproofing Systems

What is Type A Waterproofing? How and where should it be used in my basement waterproofing project?

Type B Basement Waterproofing Systems

What is Type B Waterproofing? How and where should it be used in my basement waterproofing project?

Type C Basement Waterproofing Systems

What is Type C Waterproofing? How and where should it be used in my basement waterproofing project?