Part F1 Damp and weatherproofing

NCC 2019 Volume One

Search the National Construction Code editions

State

Climate Zone

Building Classification

Classification

Part F1 Damp and weatherproofing

Performance Requirements

FP1.1 Managing rainwater impact on adjoining properties

Surface water, resulting from a storm having an average recurrence interval of 20 years and which is collected or concentrated by a building or sitework, must be disposed of in a way that avoids the likelihood of damage or nuisance to any other property.

The Objective of this Part is to—

(a)

safeguard occupants from illness or injury and protect the building from damage caused by—

(i)

surface water; and

(ii)

external moisture entering a building; and

(iii)

the accumulation of internal moisture in a building; and

(b)

protect other property from damage caused by redirected surface water.

Safeguard occupants and protect the building—FO1(a)

FO1(a) aims to minimise the risk of water leaking into or accumulating within a building and causing musty, damp and unhealthy conditions or damaging building elements by corrosion.

Examples

Damp conditions in houses can cause serious diseases. What appear to be less serious illnesses, such as colds, can have serious consequences, particularly for children and the elderly.
Rotten floorboards can collapse, causing injury.
Electrical connections can corrode, causing failure of safety devices, or increasing the risk of electrocution.
Penetration of moisture into building elements can cause degradation to a building long before the damage is detected.

Protect other property from damage—FO1(b)

FO1(b) aims to minimise the risk of other property being damaged by surface water redirected from a building or any associated sitework.

Example

Construction on an allotment must not cause re-directed water damage to “other property”, including:

any building on the same allotment;
any building on an adjoining allotment;
any adjoining allotment (whether there is a building on it or not); and
any road.

A building including any associated sitework is to be constructed in a way that protects people and other property from the adverse effects of redirected surface water.

Protection from re-directed surface water

People and other property are to be protected from any problems caused by surface water re-directed by a building and any sitework involved in its construction. Remedial works must be undertaken to dispose of any surface water which, because of any variation or addition to its flow caused by any building or sitework, causes harm to people or other property.

A building is to be constructed to provide resistance to moisture penetrating from the outside including rising from the ground.

Resistance to rain, surface water and ground water

A building must resist:

rainwater, coming through the roof or walls, due to poor waterproofing
surface water, coming through openings which are too low; and
ground water, which could rise up through porous floors or walls.

Ground water could enter a building if there are inadequate damp-proof courses or vapour barriers installed, or if other ways of resisting the rising damp have not been provided.

A building is to be constructed to avoid the likelihood of—

(a)

the creation of unhealthy or dangerous conditions; and

(b)

damage to building elements,

caused by dampness or water overflow from bathrooms, laundries and the like.

Overflow from bathrooms and laundries

The development of unhealthy conditions or damage caused by dampness or overflow from bathrooms, laundries and the like, must be prevented. Such problems may arise from showers and bathrooms being incorrectly sealed, allowing water to leak into other parts of the building.

Surface water from a 1 in 20 year storm

Surface water from a 1 in 20 year storm collected or concentrated by a building or sitework must be disposed of without damage to other property.

Construction should not cause stormwater problems on other properties, worse than those which existed previously.

Example

As a general rule, undeveloped land tends to absorb rainwater, usually resulting in comparatively slow run-off.

However, a building's hard surfaces, such as roofs and pavements, cause comparatively quick run-off. Consequently, the design of the surfacewater disposal system must make provision for run-off stormwater from hard surfaces collected or concentrated by a building or sitework.

Why 1 in 20 year storms?

The storm intensity has been limited to a 1 in 20 year storm. This is considered an appropriate limit, fair on the person responsible for the building and siteworks and the person responsible for properties affected by re-directed surface water.

FP1.2 Preventing rainwater from entering buildings

Surface water, resulting from a storm having an average recurrence interval of 100 years must not enter the building.

Limitation:

FP1.2 does not apply to—

a Class 7 or 8 building where in the particular case there is no necessity for compliance; or
a garage, tool shed, sanitary compartment, or the like, forming part of a building used for other purposes; or
an open spectator stand or open-deck carpark.

Surface water from a 1 in 100 year storm

Building and siteworks must be arranged so that surface water from a 1 in 100 year storm does not enter a building.

Why 1 in 100 year storms?

A 1 in 20 year storm has a less intense flow of water than a 1 in 100 year storm, which is what the subject building must be protected from.

It is considered more important to prevent water entering a building than it is to prevent water entering a neighbouring allotment or property.

Limitations

The limitations contain several exemptions to FP1.2. These are based on the belief that the use and safety levels of the exempted buildings will not be significantly diminished by surface water entering them.

Limitation (a) regarding Class 7 and Class 8 buildings refers only to such buildings which, in a particular case, do not exhibit any need for compliance with FP1.2. Such buildings must be considered on a case-by-case basis. However, it is the responsibility of a building proponent to satisfy the appropriate authority that the exemption should apply.

FP1.3 Rainwater drainage systems

A drainage system for the disposal of surface water resulting from a storm having an average recurrence interval of—

(a)

20 years must—

(i)

convey surface water to an appropriate outfall; and

(ii)

avoid surface water damaging the building; and

(b)

100 years must avoid the entry of surface water into a building.

Outfall, water entrance and water damage

Under FP1.3(a) a drainage system for the disposal of surface water from a 1 in 20 year storm must:

have an appropriate outfall; and
avoid damage to the building.

An outfall includes a kerb and channel, a soakage system, and a natural watercourse, with the decision as to what is appropriate being made by the appropriate authority. Damage to the building could be caused by a building's subsidence.

Under FP1.3(b), a drainage system for the disposal of surface water must avoid surface water from a 1 in 100 year storm from entering a building. This provision is intended to prevent surface water causing internal damage to a building, or causing injury or illness to occupants.

The FP1.3(b) prohibition on surface water entering the building:

does not prohibit a drainage system that passes surface water through a building (probably by way of pipes) without causing damage; and
clearly does not prohibit water entering a building when it is required for various purposes.

FP1.4 Weatherproofing

A roof and external wall (including openings around windows and doors) must prevent the penetration of water that could cause—

(a)

unhealthy or dangerous conditions, or loss of amenity for occupants; and

(b)

undue dampness or deterioration of building elements.

Limitation:

FP1.4 does not apply to—

a Class 7 or 8 building where in the particular case there is no necessity for compliance; or
a garage, tool shed, sanitary compartment, or the like, forming part of a building used for other purposes; or
an open spectator stand or open-deck carpark.

Roofs and walls to prevent water penetration

Roofs and walls (including windows, doors and other openings in the walls) must prevent water penetration which could cause dangerous conditions, loss of amenity or dampness and deterioration of building elements.

Limitations

The limitations contain several exemptions to FP1.4. These are based on the belief that the use and safety levels of the exempted buildings will not be significantly diminished by water entering them.

Limitation (a), regarding Class 7 and Class 8 buildings, refers only to such buildings which, in a particular case, do not exhibit any need for compliance with FP1.4. Such buildings must be considered on a case-by-case basis. However, it is the responsibility of a building proponent to satisfy the appropriate authority that the exemption should apply.

FP1.5 Rising damp

SA FP1.5

Moisture from the ground must be prevented from causing—

(a)

undue dampness or deterioration of building elements; and

(b)

unhealthy or dangerous conditions, or loss of amenity for occupants.

Limitation:

FP1.5 does not apply to—

a Class 7 or 8 building where in the particular case there is no necessity for compliance; or
a garage, tool shed, sanitary compartment, or the like, forming part of a building used for other purposes; or
an open spectator stand or open-deck carpark:

Moisture from the ground

Building elements must be protected from deterioration and occupants must be protected from unhealthy or dangerous conditions or a loss of amenity caused by moisture from the ground (causing such problems as rot, rising damp, rust, and so on). In essence, this requires that the materials and components which make up building elements must either be fit for this purpose or made fit by protection.

Examples

The following may be acceptable to achieve compliance with FP1.5. They should not be regarded as absolute.

damp-proof course in masonry walls above finished ground level;
vapour barrier under a concrete slab;
adequate subfloor ventilation;
painted or other similar protective coatings on steel and timber on or near ground level;
appropriate concrete cover on steel reinforcing;
galvanised coatings on steel; and
specific concrete mixes to achieve required protection levels.

FP1.6 Wet area overflows

SA FP1.6

Overflow from a bathroom, laundry facility or the like must be prevented from penetrating to—

(a)

another sole-occupancy unit used for sleeping accommodation; and

(b)

a public space,

in a storey below in the same building.

Water overflows from bathrooms and laundries

Water overflows from bathrooms, laundries and the like must be prevented from penetrating downwards—i.e. to a storey below—to either another sole-occupancy unit used for sleeping accommodation or a public space. Such overflows are potentially unhealthy and structurally damaging, and can be disruptive for neighbours.

FP1.7 Wet areas

To protect the structure of the building and to maintain the amenity of the occupants, water must be prevented from penetrating—

(a)

behind fittings and linings; and

(b)

into concealed spaces,

of sanitary compartments, bathrooms, laundries and the like.

SA FP1.8

Water — fittings, linings and concealed spaces

The structure of a building and the amenity of its occupants must be protected by preventing water from penetrating behind fittings and linings and into concealed spaces of toilets, bathrooms, laundries and the like.

Verification Methods

FV1.1 Weatherproofing

(a)

Compliance with FP1.4 for weatherproofing of an external wall that—

(i)

has a risk score of 20 or less, when the sum of all risk factor scores are determined in accordance with Table FV1.1; and

(ii)

is not subjected to an ultimate limit state wind pressure of more than 2.5 kPa; and

(iii)

includes only windows that comply with AS 2047,

is verified when a prototype passes the procedure described below:

(iv)

The test specimen is in accordance with the requirements of (b).

(v)

The test procedure is in accordance with the requirements of (c).

(vi)

The test specimen does not fail the criteria in (d).

(vii)

The test is recorded in accordance with the requirements of (e).

Table FV1.1 – Risk factors and scores

Risk factor	Category	Risk severity	Score
Wind region	Region A (AS/NZS 1170.2)	Low to medium	0
	Region B (AS/NZS 1170.2)	Low to medium	0
	Region C (AS/NZS 1170.2)	High	1
	Region D (AS/NZS 1170.2)	Very high	2
Number of storeys	One storey	Low	0
	Two storeys in part	Medium	1
	Two storeys	High	2
	More than two storeys	Very high	4
Roof/wall junctions	Roof-to-wall junctions fully protected	Low	0
	Roof-to-wall junctions partially exposed	Medium	1
	Roof-to-wall junctions fully exposed	High	3
	Roof elements finishing within the boundaries formed by the external walls	Very high	5
Eaves width	More than 600 mm for single storey	Low	0
	451-600 mm for single storey; or	Medium	1
	more than 600 mm for two storey	Medium	1
	101-450 mm for single storey; or	High	2
	451-600 mm for two storey; or
	more than 600 mm for above two storey
	0-100 mm for single storey; or	Very high	5
	0-450 mm for two storey; or
	less than 600 mm for above two storey
Envelope complexity	Simple shape with single cladding type	Low	0
	Complex shape with not more than two cladding types	Medium	1
	Complex shape with more than two cladding types	High	3
	As for high risk but with fully exposed roof-to-wall junctions	Very high	6
Decks, porches and balconies	None; or	Low	0
	timber slat deck or porch at ground level	Low	0
	Fully covered in plan view by roof; or	Medium	2
	timber slat deck attached at first or second floor level	Medium	2
	Balcony exposed in plan view at first floor level; or	High	4
	balcony cantilevered at first floor level	High	4
	Balcony exposed in plan view at second floor level or above; or	Very high	6
	balcony cantilevered at second floor level or above	Very high	6

Notes to Table FV1.1 :

Eaves width is measured horizontally from the external face of any wall cladding to the outer edge of any overhang, including fascia and external gutters.
Barriers to prevent falling and parapets are considered as 0 mm eaves.

(b)

Test specimen

The test specimen must incorporate—

(i)

representative samples of openings and joints, including—

(A)

vertical and horizontal control joints; and

(B)

wall junctions; and

(C)

windows or doors; and

(D)

electrical boxes; and

(E)

balcony drainage and parapet flashings; and

(F)

footer and header termination systems; and

(ii)

for a cavity wall—

(A)

a transparent material for a proportion of the internal wall lining (to provide an unobstructed view of the external wall cladding) with sufficient structural capability and similar air tightness to resist the applied wind pressures; and

(B)

a 15 mm diameter hole in the internal wall lining below a window.

(c)

Test procedure

(i)

The test procedure for a direct fix cladding wall or unique wall must be as follows:

(A)

Apply 100% positive and negative serviceability wind pressures to the external face of the test specimen for a period of not less than 1 minute each.

(B)

Apply static pressure of either 300 Pa or 30% serviceability wind pressure, whichever is higher, in accordance with the water penetration test procedure at clause 8.5.2 of AS/NZS 4284.

(C)

Apply cyclic pressure in accordance with—

(aa)

the three stages of Table FV1.2; and

(bb)

the water penetration test procedure at clause 8.6.2 of AS/NZS 4284.

Table FV1.2

Stage number	Serviceability wind pressure
1	15% to 30%
2	20% to 40%
3	30% to 60%

(ii)

The test procedure for a cavity wall must be as follows:

(A)

Apply 100% positive and negative serviceability wind pressures to the external face of the test specimen for a period of not less than 1 minute each.

(B)

Apply static pressure of either 300 Pa or 30% serviceability wind pressure, whichever is higher, in accordance with the water penetration test procedure at clause 8.5.2 of AS/NZS 4284.

(C)

Apply cyclic pressure in accordance with—

(aa)

stage 3 of Table FV1.2; and

(bb)

the water penetration test procedure at clause 8.6.2 of AS/NZS 4284.

(D)

To simulate the failure of the primary weather-defence or sealing, the following procedure must be applied to the test specimen:

(aa)

Insert 6 mm diameter holes through the external face of the cavity wall in all places specified below:

(AA)

Wall/window or wall/door junctions at ¾ height.

(BB)

Immediately above the head flashing.

(CC)

Through external sealing of the horizontal and vertical joints.

(DD)

Above any other penetration detail not covered by (AA) to (CC).

(bb)

Repeat the static and cyclic pressure tests of (B) and (C).

(cc)

Within 30 minutes of the completion of (bb), remove the internal lining of the cavity wall and check for compliance with (d).

(dd)

With the internal lining removed, apply a final static pressure test at 50 Pa for a period of 15 minutes.

(d)

Compliance

(i)

A direct fix cladding wall and unique wall are verified for compliance with FP1.4 if there is no presence of water on the inside surface of the facade.

(ii)

A cavity wall is verified for compliance with FP1.4 if there is no presence of water on the removed surface of the cavity, except that during the simulation of the failure of the primary weather-defence or sealing, water may—

(A)

transfer to the removed surface of the cavity due to the introduced defects (6 mm holes); and

(B)

contact, but not pool on, battens and other cavity surfaces.

(e)

Test report

The test report must include the following information:

(i)

Name and address of the person supervising the test.

(ii)

Test report number.

(iii)

Date of the test.

(iv)

Cladding manufacturer's name and address.

(v)

Construction details of the test specimen, including a description, and drawings and details of the components, showing modifications, if any.

(vi)

Test sequence with the pressures used in all tests.

(vii)

For each of the static and cyclic pressure tests, full details of all leakages, including position, extent and timing.

FV1.1 is a means to verify whether or not a proposed external wall achieves the requirements of FP1.4, i.e. whether the wall prevents the penetration of water that could cause:

unhealthy or dangerous conditions or loss of amenity for occupants; and
undue dampness or deterioration of building elements.

FV1.1 is not a mandatory component of the NCC, however it is one form of assessment method which can be used to demonstrate compliance with the Performance Requirements.

Other assessment methods in the NCC include:

evidence to support that the use of a material, form of construction or design meets the Performance Requirement or a Deemed-to-Satisfy Provision;
comparison with a Deemed-to-Satisfy Provision where applicable; or
expert judgement, which means the judgement of an expert who has the qualifications and experience to determine whether a solution complies with the Performance Requirements.

The Verification Method must be applied in the following order:

confirm the limitations of FV1.1(a)(i) to (iii) are met;
develop a test specimen including representative samples of openings and the like (FV1.1(b));
test the specimen in accordance with the relevant test procedure (FV1.1(c));
assess the specimen against the compliance criteria (FV1.1(d)); and
record the test results (FV1.1(e)).

This process is shown in Figure FV1.1(1).

Figure FV1.1(1)

Risk factors—Table FV1.1

The risk score is determined by a number of factors including:

wind region;
number of storeys;
type of roof/wall junctions;
eave widths;
complexity of the building envelope; and
types of decks and balconies.

The following are examples of typical roof/wall junctions and their associated exposure or protection categories:

a hip and gable roof with eaves is considered to have fully protected roof-to-wall junctions;
a hip and gable roof with no eaves is considered to have partially exposed roof-to-wall junctions;
parapets, enclosed barriers or eaves at greater than 90° to vertical with soffit lining are considered fully exposed roof-to-wall junctions; and
lower ends of aprons, chimneys, dormer windows and the like are considered roof elements finishing within the boundaries formed by the external walls.

Building envelope complexity is determined by the shape and the amount of cladding used. FV1.1 includes both simple and complex shaped buildings:

A simple shaped building includes rectangular, L or T shaped buildings.
A complex shaped building includes a building with angular or curved shapes such as a Y shaped building.

Test specimen—FV1.1(b)

Representative samples of openings and joints must be included to test the whole cladding system.

This includes samples of:

vertical and horizontal control joints;
wall junctions;
windows or doors;
electrical boxes;
balcony drainage (i.e. to prevent water pooling against the external wall) and parapet flashings; and
footer and header termination systems (i.e. a header termination system is where a cladding finishes at the top of a window).

A test specimen is illustrated in Figure FV1.1(2).

Figure FV1.1(2)

Where a cavity wall is tested, a transparent material must be used in lieu of a portion of the internal wall lining. The transparent material will be used during the testing to observe any water penetration. To ensure an unobstructed view of the external wall occurs, other building components such as building membranes must be removed for the extent of the transparent opening within the internal wall lining. It should be noted that for the purposes of FP1.4 building membranes are not a requirement. However a membrane can be used to achieve compliance with FV1.1.

The transparent material must be installed to maintain similar air tightness as the intended internal wall lining. To simulate the effects of power points, light switches and other similar openings which may cause air leakage, a 15 mm diameter hole must be placed in the internal wall lining below the window.

Test procedure—FV1.1(c)

The test procedure requirements vary in relation to two sub-clauses. FV1.1(c)(i) specifies the test procedure for a direct fix cladding wall or a unique wall. FV1.1(c)(ii) specifies the requirements for cavity wall construction. The difference between the two sub-clauses is FV1.1(c)(ii) has an additional water management test. This is due to cavity wall construction being designed to allow water to pass through the primary weather-defence (e.g. the skin of masonry on a masonry veneer wall), with the function of the cavity allowing for the removal of any water.

Direct fix cladding wall and unique wall—FV1.1(c)(i)

The test procedure for FV1.1(c)(i) contains three steps:

Apply a preconditioning loading to the external face of the wall, by placing 100% positive and 100% negative (suction) serviceability wind pressure to the external wall. The serviceability wind pressure will be determined by the location in which the wall is going to be installed. However, due to the limitations of the Verification Method, the ultimate state wind pressure can be a maximum of 2.5 kPa. For a vented cavity wall, the end sections of the cavity must be sealed and the material serving as the air seal must be able to withstand the same applied loading as the wall being tested.
Conduct a static pressure test at 30% of the serviceability wind pressure or 300 Pa, whichever is higher. FV1.1(c)(i)(B) refers to clause 8.5.2 of AS/NZS 4284 for the requirements of this test.
Conduct a cyclic pressure test in accordance with clause 8.6.2 of AS/NZS 4284, tested over the three stages specified in Table FV1 . 2.

Cavity walls—FV1.1(c)(ii)

The test procedure for FV1.1(c)(ii) contains four steps:

The first two steps are identical to FV1(c)(i) in respect to the preconditioning loading test and the static pressure test.
The third test, the cyclic pressure test, is slightly different to the cyclic pressure test in FV1.1(c)(i). The test is still required to be in accordance with clause 8.6.2 of AS/NZS 4284. However, instead of testing three stages of Table FV1 . 2, FV1.1(c)(ii)(C) only requires one test, using serviceability wind pressures of stage three of Table FV1.1. Only one cyclic pressure test is required as the water management test in FV1.1(c)(ii)(D) requires additional tests; one additional cyclic test and two additional static pressure tests.
FV1.1(c)(ii)(D) contains the additional testing requirements for a cavity wall. This test represents the failure of the primary weather defence or sealing. The primary weather defence includes the wall material, any flashings and sealing of joints and openings.

Compliance—FV1.1(d)

Similar to the test procedure, the compliance requirements are separated into two parts and are subject to the type of wall being tested.

FV1.1(d)(i) specifies the compliance requirements for a direct fix cladding wall and a unique wall. Compliance for the testing of these types of walls is met by no presence of water to the inside surface of the facade. This includes the surface of the external wall which is fixed to the internal wall, or for a single skin wall, the internal wall.

The compliance requirements for a cavity wall in FV1.1(d)(ii) are different to the requirements for a direct fix cladding wall or unique wall. This is due to the purpose and nature of a cavity wall. Water which passes through the primary weather-defence will gradually be removed from the cavity either through weep holes or evaporation. FV1.1(d)(ii) therefore allows water to enter the cavity provided water is not present on the removed surface of the cavity. However, there are some exemptions to this, as the water may transfer to the removed surface through an isolated blemish due to the introduced defects. Also, water can contact cavity surfaces such as battens. However, it must be demonstrated that the water will be able to be removed from these surfaces.

The removed surface of the cavity will generally be the outer surface of the internal wall, for example, where the building membrane would be attached to a stud frame.

The purpose of the test report in FV1.1(e) is to record the details and the outcomes of the test. This is common for any test procedure.

FV1.2 Overflow protection

FP1.6 is verified when the flow rate of the in-built overflow for all vessels in the room is greater than the flow rate of the source filling the vessel.

Application:

FV1.2 only applies to bathrooms, laundries and the like in a Class 2 or 3 building or a Class 4 part of a building.

FV1.2 allows the use of vessels with built-in overflow to provide overflow capacity rather than through the use of a floor waste or other means.

Filter

Part F1 Damp and weatherproofing

Performance Requirements

FP1.1 Managing rainwater impact on adjoining properties

Example

FP1.2 Preventing rainwater from entering buildings

Limitation:

FP1.3 Rainwater drainage systems

FP1.4 Weatherproofing

Limitation:

FP1.5 Rising damp

Limitation:

Examples

FP1.6 Wet area overflows

FP1.7 Wet areas

Verification Methods

FV1.1 Weatherproofing

FV1.2 Overflow protection

Application: