Booklet 6 Building in a Saline Environment

7/28/2019 Booklet 6 Building in a Saline Environment

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Copyright held by the State of NSW and Department of Environment and Climate Change.

Published by:Department of Environment and Climate Change NSW5961 Goulburn StreetPO Box A290Sydney South 1232

Building in a Saline Environment

ISBN - 978 07347 59702

DECC 2008/415Second edition printed August 2008. First edition printed 2003 by the formerDepartment of Infrastructure, Planning and Natural Resources

While every reasonable effort has been made to ensure that this document is correct at thetime of publication, the State of New South Wales, its agencies and employees, disclaim anyand all liability to any person in respect of anything or the consequences of anything done oromitted to be done in reliance upon the whole or any part of this document.

Acknowledgements: NSW Department of Primary IndustriesSydney Metropolitan Catchment Management Authority


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Contents

Introduction....................................................................................................................................2

Sources of Salt ..............................................................................................................................3

Sources of Water .........................................................................................................................4

Infiltration Rates .........................................................................................................................5

Porosity vs Permeability...........................................................................................................5

The Reactions of Salts with Building Materials ...................................................7

Concrete ..........................................................................................................................................8

Bricks Resistant to Salt and Water ................................................................................9

Concrete Resistant to Salt and Water ......................................................................10

Preventing Water and Salt Moving Into the Building................................. 11

Damp Proof Membranes ....................................................................................................... 12

Maintaining Good Drainage on a Building Site ...............................................13

Building Codes ...........................................................................................................................14

Australian Standards ............................................................................................................ 16


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Introduction

Salts are a natural part of the Australianlandscape. Concentrated salts and differenttypes of salts once dissolved and mobilised inwater, can have an impact on the durabilityof some building materials.

This booklet is part of the Local GovernmentSalinity Initiative series and looks at:-

how salts enter building materials,1.

the effect of salt and water on some2.building materials,

information available for building in3.saline environments.

Other booklets in the Local GovernmentSalinity Initiative series related to buildingsinclude Repairing and Maintaining Salinity

Affected Houses, Indicators of UrbanSalinity, Site Investigations for Urban Salinityand Land Use Planning and Urban Salinity.

Bricks showing signs of salt and water damage.

Paintwork blistering due to the accumulation of salts .

A sandstone church showing signs of salt and water damage.

A verandah post showing signs of salt and water damage.

Render showing signs of salt and water.

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Sources of Salt

Building products are made with variousmaterials such as sand, aggregates andwater that may contain salts. Alternativelythe finished product may be stored in alocation which allows the addition of saltscarried by wind, rain or from the ground

to enter the finished product.

Once the product is used in a building,sources of moisture, wind or rain can addmore salts. Various coatings or treatmentsmay also add to the type and quantityof salts present. For example magnesitewas commonly used on the floors ofapartment blocks during the 1960s and70s to provide a fast level finish to the floorand for sound proofing. It has since beenfound that salts can leach out of the productand cause corrosion in the reinforcingwithin the concrete.

It is important to understand the source orsources of salts in order to determine themost effective course of action, if action isneeded. For example layers of salty soil deepunder ground are unlikely to be an issue if awater source is not bringing the salts to thesurface and extensive cut and fill is avoided.

New bricks releasing salts.

New pavers laid on unwashed sand.


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Sources of Water

The Building Code of Australia, hasobjectives and performance requirementsto prevent undue dampness and moisturedamage. Complying with these is veryimportant for preventing salt movement andsalt damage. Salts dissolve in water. They

can therefore move with water into andaround buildings. Houses impacted by urbansalinity often have several water sourcescontributing to the salt attack.

Water sources include:

Rising damp , where soil moisture isdrawn up into the building material bycapillary action. The ground moisturemay be a result of one or several watersources near the building, on surrounding

properties or further afield. For example,a leaking pipe may cause damp groundnear the leak. A leaking pool may affectseveral houses, while numerous leakystructures and activities like the overwatering of parks and gardens around atown may result in a high groundwatertable that affects several sites, suburbs orthe whole town.

Falling damp , where leaking gutters,downpipes or roofs allow water to run

down the outer face of the building orinto the wall cavity. Movement of water ismostly downward due to gravity howeverwater may soak into building materialsas it runs down over the building oraccumulates at the base of the building.

Condensation , where water vapour inthe air condenses on cooler wall surfaces.Examples can include hot moist air fromclothes dryers, cooking, showers andunventilated combustion heaters.

Courthouse showing symptoms of falling damp possibly froma blocked gutter.

A rusted down pipe allowing rainwater to mobilise saltsin the soil.

A building with wet tide mark ( dark bricks ) showing theheight of the rising damp.

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Porosity vs Permeability

A material may be porous but notpermeable. That is, a material may have lotsof pore spaces but at the same time notallow water to pass through it. If pores are

isolated or closed, if they have a lining thatcan react with fluid to discourage movement,or are too small to be filled as the air theycontain cannot escape, then the material isconsidered to have a low permeability.

Pore size varies between materials but alsowithin a material. In theory, a pore size of0.001 mm can support a 1m high columnof water. If salts are present in the water thenthe surface tension of the water is increasedand there is increased pull up the poretube. This is partially offset by the increasedweight of the water column due to the saltsdissolved in the water.

Pore diameters in mortar and brickwork arein the range of 0.1 um (0.0001 mm) to 10um (0.01 mm) and can act as capillary tubes.Fine cracks in concrete and other productscan also act as capillary tubes.

Bricks that have crumbled grain by grain as a resultof salt hydration and crystallisation.

Infiltration Rates

The three main factors driving the rate ofwater ( and salt ) entering a building are the

Amount of available water1. . This isinfluenced by the depth to the watertable; the amount of water leaking from

water, sewer and stormwater systems; theover watering of gardens; as well as thetiming, distribution and intensity of rain.

Rate of evaporation2. . This is affected

by such things as ventilation, temperature,

relative humidity and the amount of

building surface exposed to evaporative

processes. Water is drawn towards the

building surface where evaporation occurs.

Permeability of the building material3. .The size, distribution and continuity

of the pores within a building materialdetermines how easily water can enterand travel through a building material.

Since salts are mobilised by water, infiltrationrates are very important in controllingsalinity impacts. However, if salts have beenaccumulating for some time and the sourcesof water then controlled, salinity damagewill continue to occur. This is because somesalts will attract moisture from humid air. Thehydration and recrystallisation of these saltswill continue to exert physical pressure onthe building. Also in some areas water tablestake a long time to respond to changesin water management.


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Exaggerated diagram of capillary rise in various size tubes.

Source: Department of Environment and Natural Resources(1995), Rising Damp and Salt Attack, State Heritage Branchand City Of Adelaide.

A render with low permeability may reduce evaporationso more water is available to travel up the wall. In thisphoto, evaporation is occurring just above the top of therender, concentrating salts and resulting in the crumblingof the brickwork.

Moisture moves through material towardsthe surface where evaporation is occurring.The tide mark or height of the wateron a wall is the point where the rate ofevaporation equals the amount of watergetting into and moving through the wall.Construction that maintains low permeability,allows increased ventilation and decreasedcontact between building materials andsources of water are therefore less proneto salt and water damage.

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Brick work showing signs of salinity damage andaccumulation of brick grains at the base of the wall.

The Reactionsof Salts withBuilding Materials

Once water and salts are absorbed bybuilding materials, chemical and physicaldamage can result. The extent of chemicalattack will depend on the concentrations andparticular types of salts present, as well as thecomposition of the building material.

Physical attack on the other handrequires a wetting and drying process.Salts form crystals as the moisture in whichthey are dissolved evaporates. A largecrystal will exert physical pressure on thebuilding material surrounding it. Newmoisture allows the crystal to dissolve,move and grow as more salts are suppliedin the water.

Different salts form different sized crystalsand even the same salt forms differentsized crystals under different conditions.These crystals can expand with heat. Theeffect on the building material will dependon the location of the crystal within thebuilding material as well as the physicalproperties and cohesive strength of thebuilding material.

Wetting and drying cycles can alsosignificantly increase the concentrationof salts over the life span of the building.In a brick veneer building for example,evaporation is most likely to be highest onthe outside wall of the northern side ofthe building. Higher levels of evaporationlead to a greater concentration of salts andmore damage provided there is a supplyof salt and water. The supply of water maybe intermittent over the lifespan of the

building or occur regularly over a portion ofthe houses history until the water source isrepaired or redirected.

Bricks showing symptoms of salinity damage while themortar in this case, is slightly more resistant to the physicalforces exerted by the salts.


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saline soils to improve the soil properties forlandscaping and soil erosion purposes. Thelevel of gypsum applied should be taken intoaccount when designing concrete structures.

Chlorides do not react chemically withconcrete. However, wetting and dryingcycles, changes in humidity and temperature,can result in the formation of salt crystals

that exert a physical stress on concrete.Cement containing higher proportions oftricalcium aluminate may be less susceptibleto chlorides. Chloride ions can react with thetricalcium aluminate in the cement to forman insoluble new product thus renderingpart of the chlorides harmless.

Carbonates can decrease the alkalinityof the cement paste from around pH 12to pH 9.5. This decreases the resistance ofthe reinforcing metal within some concrete

structures, to corrosion.Corrosion of reinforcement in concrete

occurs in two phases, namely initiation and

propagation. The initiation phase is where

concrete alkalinity is reduced by carbonation

or ionization. Carbonates may come from

sources such as groundwater or carbon

dioxide in the air. lonization occurs where

there is a higher concentration of reactive ions

such as chlorides. Chlorides sources include:

groundwater, the soil, the atmosphere, acid

etching, admixtures, or the water, aggregateand sand, used to make the concrete. Once

initiated, the propagation phase of the

corrosion continues at a rate dependent on

the amount of available oxygen, moisture,

reactive ions and remaining alkalinity.

It is therefore important to know the salttypes, salt levels and water sources on thebuilding site at the time of construction andwhat is likely throughout the lifespan of thebuilding. This knowledge allows the choice

of suitable building materials and techniquesto avoid potential physical and chemical saltdamp attack.

Rust formation exerts physical pressure on the surroundingconcrete and leads to weakening of the reinforcement steel.

Concrete

Generally, chemicals in their dry state do notattack concrete. However, once mobilisedin water, various chemical and physicalinteractions can occur.

Acids dissolve the alkaline components of

concrete eg calcium hydroxide to form soluble

salts. These can be leached from the concrete,

increasing its porosity and decreasing itsstrength. Concretes containing blast furnace

slag or fly ash have less calcium hydroxide

than other non blended products and are

therefore less susceptible to acid attack.

Sulphates react with the hydrated calciumaluminate component of cement. Theproducts of these reactions have a largervolume than the original ingredients andexert a physical stress on the concrete.The rate of sulphate attack is affected byfactors such as the solubility of the differentsulphates. For example, calcium, magnesiumand sodium sulphates have differentsolubilities. Also the process is exacerbatedif magnesium and /or ammonium arepresent as they attack the silicates andcalcium hydroxide components not justthe calcium aluminates.

Sulphate resistant cement is often calledmarine grade and contains only smallamounts of calcium aluminates. Note thatcalcium sulphate (gypsum) is often applied to

Concrete kerb and gutter affected by sulphates.

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Ideally the designer, builder, brickmanufacturer, brick purchaser and buildingcertifier should all be aware of the issue ofsalt attack and brick classification.

Within a style of bricks some are usuallyexposure grade and others general purpose,with no price differential. Therefore it ispossible, at no extra cost, to use exposure

grade bricks as a precaution againstunknown, present or future salt attack.

Choosing a brick product with a lower initialsalt content is not mentioned in the BCA.However there is an Australian Standard fortesting the salt content of bricks, AS4456.6Masonry Units and Segmental Pavers -Methods of Test - Determining Potential toEffloresce. This means choosing productswith minimal existing salt content could bean easy to implement added precaution for

building sites with existing high salt levels.

Bricks Resistant toSalt and Water

The Building Code of Australia (BCA)requires moisture control to preventdamage, dampness, deterioration, loss ofamenity, unhealthy or dangerous conditions.

Acceptable construction practices ordeemed to satisfy provisions to achieve theseobjectives and performance requirementslisted in the BCA include the classificationof masonry units and their use inappropriate areas.

The BCA lists exposure class bricks asSuitable for use in all classificationsincluding severe local conditions such as:

below the damp-proof course in areasa.where walls are expected to be attackedby salts in the groundwater or brickworkitself (salt attack or salt damp)...

The method for classifying bricks is furtherdescribed in Australian Standard 3700Masonry Units which in turn refers to a saltresistance test which is described in detailin Australian Standard 4456.1 MasonryUnits and Segmental Pavers - Method ofDetermining Resistance to Salt Attack. Thetest involves soaking five bricks in a salt

solution, drying the bricks then repeating theprocess 39 times. The weight of the bricksbefore and after this process is comparedto measure how much of each brick hascrumbled away due to salt attack.

Exposure class bricks are those that loseless than 0.4g of weight after 40 wettingand drying cycles or where a supplier candemonstrate that the product has a historyof surviving in saline environments.

The BCA also gives the ratio of cement,

lime and sand suitable for mortars usedwith exposure class bricks and prohibits theuse of raked mortar joints with exposureclass bricks.


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In order to improve the durability of concretein moist saline environments consider:

using a quality assurance certified cement

manufacturer, concrete batcher andsupplier

the water to cement ratio do not addextra water on site

curing procedures and duration

choice of concrete eg sulphate resistant orhigher strength, to suit the site conditions

vibration to remove entrapped air andensure good placement in and around

the reinforcing and formwork

increasing the amount of concrete coverover steel reinforcement

minimising cracks in the final structure

minimising ponding of water on or nextto concrete

All other factors being equal, increasingconcrete strength will decrease itspermeability. As there is no standard test

for permeability in cement, strength isoften used as an indicator of permeability.However, this is an oversimplificationand should not be used as the onlyspecification or design criteria for ensuringconcrete structures are durable in salinityhazard landscapes.

Concrete Resistantto Salt and Water

Concrete is a mixture of coarse and fineaggregate, cement and possibly otheradditives such as fly ash, slag or chemicaladmixtures added to enhance properties

of the concrete for specific purposes.Concrete forms by the chemical reactionof hydration, where water reacts chemicallywith the cement to form new compounds.The hydrated cement paste forms ribbon-likecrystals that interlock and bind together thesand and gravel to form concrete.

Larger quantities of concrete are delivered to the building sitewhile smaller amounts and cement based mortars and rendersare often mixed on site.

Protecting concrete from excessive water loss during thefirst seven days after placement has a dramatic impact onthe permeability of the final product.

The strength and permeability of the finalconcrete relies on several factors includingthe product ingredients and proportions, aswell as the handling of the product when it isdelivered and hydration is occurring.

A builder generally orders a particular type,strength and quantity of concrete. Thisdetermines the water to cement ratio, size,type and amount of aggregate, sand andcement in the mix. The builder then placesthe concrete within the formwork and

around the metal reinforcing, vibrating outtrapped air, and protecting the concretefrom processes that will cause excessiveevaporation. Without good handlingprocedures, the final product will not achievethe correct strength. Adding extra water,over vibration, too little vibration, and poorcuring methods, all result in a weaker morepermeable concrete.

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A DPC if installed correctly as a continuousbarrier around the house should stop theupward movement of rising damp.

However a DPC may fail for a numberof reasons:

breakdown due to chemical attack

cracking or penetration during installation

breakage by differential settling of thebuilding

incorrect installation

bridging by pointing or rendering

bridging by the installation of gardenbeds and paving

bridging by mortar droppings collecting inthe wall cavity

bridging by renovations or additions, eg

incorrect replacement of a timber floorwith sand and a concrete slab.

Once the DPC is bridged or broken, waterand salts are able to move upwards throughcapillary action. This significantly increasesthe difficulty and cost of repairing salinitydamage to buildings. Correctly installingand maintaining a durable DPC is thereforean important technique in controlling saltdamage to buildings.

The South Australian Salt Damp ResearchCommittee, in their Second Report (1978),stated, Protection against salt damp isdependent upon each link in a continuouschain competent design and specifications,painstaking construction, skilled supervision,good housekeeping and maintenance by theowner/occupier. It is logical that this theoryholds true today.

Bridging the DPC: some examples

DPC DPC

concrete floor

sand fill

Raised garden bed provides amoisture path above DPC

1Plaster brought down over DPCcreates bridge

In this case the DPC shouldhave been installed below allfloor timbers

2Pointing or repointing overthe DPC

A render over the DPC wouldsimilarly create a bridge

3Concrete floor laid across (orabove) the DPC without aseparating moisture barrier

External paths can alsocreate bridges

4

floor joist

Source:Department

ofEnvironmentandNaturalResources(19

95),

RisingDampandSaltAttack,StateHeritageBranchandCity

ofAdelaide.

Preventing Salt andWater Moving intothe Building

The Building Code of Australia (BCA)deemed to satisfy provisions to meet themoisture control requirements, also includesinstallation of a damp proof course belowfloor level. In the past, damp proof courseshave been made of various materialsincluding coal tar, slate, coated metals, andmortars containing chimney soot. Today, itis common for the damp proof course to bepolyethylene sheeting laid in a horizontalmortar joint of the brick work.

Acceptable building practice in the BCAstates that the damp proof course (DPC)should be 150mm above the finished groundlevel or 100mm if the ground is sandy andwell drained. This can be further reducedto 50mm if the area is finished with pavingor concreting that slopes away from thebuilding and is covered by a verandah.

This installation of a polyethylene damp proof course isunlikely to comply with the deemed to satisfy provisionsregarding height above finished ground level.


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Damp Proof Membranes

It is common practice at present, to constructhouses with concrete floors essentially layingat ground level. For moisture control in thesehouses the deemed to satisfy provisions inthe BCA for New South Wales (NSW) andSouth Australia (SA) include installation of ahigh impact resistant 0.2mm polyethylene

damp proof membrane as a continuous layerunder the slab and wrapped around thefootings to ground level.

This provision was introduced in May 2004 inNSW as a state variation to the Building Codeof Australia to better protect houses againstthe effects of urban salinity.

Damp proof membranes are more resistantto puncture than the low impact resistantvapour proof membranes. Membranes arelaid on the excavated and prepared siteprior to placement of reinforcing, concreteformwork and concrete. Builders thereforehave to walk on the membrane. A highimpact resistant membrane is less likely tobe pierced by stones caught in the tread ofthe builders boots or protruding from theground below the plastic.

Prior to the 2004 NSW BCA amendment,

builders in all states except SA, were required

to use high impact resistant damp proof

membranes only in areas prone to risingdamp and salt attack. This meant builders

had to be aware of the provision of when

a low impact resistant vapour barrier was

not acceptable as well as be aware of local

rising damp and salt attack issues. Policing by

building certifiers was also difficult as both

types of membranes are available in orange

and black, the membranes are laid with

the printed branding face down, and the

membrane is covered by concrete early in the

construction process. These difficulties are

minimised with the NSW and SA requirement

for the standard use of high impact damp

proof membranes on all house sites.

There is only a small price differential between

the low impact and high impact membranes

while repair of salt attack is expensive.

The potential for salt attack during the lifespan

of a house is high and widespread. Australia

is one of the most saline continents in the

world and all urban house sites have some

water sources that may mobilise these salts.Cost effective precautions to salt attack are

therefore justified.

Damage limited to the area below the damp proof course.

Damp-proof course bypassed by rendering.

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Maintaining GoodDrainage ona Building Site

The movement of water and mobilisation ofsalts at various scales needs to be consideredwith respect to house construction anddrainage on the building site. On acatchment scale, water may be entering agroundwater system kilometres away fromwhere the water returns to the surface.

Along the way this water may have pickedup salt from the rocks and soils it has passedthrough. In this situation on-site action aswell as work further up the catchment suchas increasing perennial vegetation, wherethe water is getting into the groundwatersystem, could be more cost effective.

On an urban subdivision scale, decisionssuch as whether to use septic tanks, irrigatelarge areas, infiltrate stormwater, supplypiped potable water, how much nativevegetation is retained, all impact on thesalt and water movement. A salt and waterbalance at the planning stage can estimatethe impact of these changes within thesubdivision and surrounding area. If theenvironmental, social and economic costs aretoo high, alternative decisions may be made

about the nature and type of development,or a management plan put in place to dealwith any adverse impacts. In western Sydney,salinity management plans submitted bydevelopers of large new estates ofteninclude drainage and additional building/construction requirements to address thesalt and water issues of the region.

This property is located where high groundwater levels area result of the catchment shape and land uses. Installation ofextra air vents and more efficient vents is unlikely to preventsalt damage. Moisture barriers and salt resistant materials maybe a more effective choice.

Part of Figure 3.3.4.1, Volume 2 of the BCA. Note Dampproof barrier not vapour barrier required in NSW and SA. Thisbarrier underlays the slab, wraps the footings and is finishedat ground level. The slope away from the building is a drop of50mm over the first 1m.

Damage to brick piers discovered during a building inspection.

Some NSW councils (eg Wagga Wagga,Camden, Junee and Fairfield) recommendor require via local building policies, the useof a 50mm layer of sand under the highimpact damp proof membrane. This is anadded precaution against puncture but also

improves drainage and minimises capillaryrise of moisture from the soil. Many buildersalso use sand to prepare a site for the layingof the concrete slab, offsetting the cost1by shorter site preparation times and lessconcrete wastage.

Prior to slab on ground construction being sopopular, floors rested on bearers and joists,supported by piers. This type of constructionhas less building material in contact withpossible salt and water sources in the soil. It

more readily allows ventilation, evaporationand the concentration of salts to occur inthe soil rather than building materials. Thebuilding is also less likely to impact on naturalsalt and water processes. The deemed tosatisfy provisions in the BCA require thespace between the ground and suspendedfloor to be a minimum clearance of 400mmin houses that require termite management.Ease of access for termite inspection alsoallows a visual inspection for salinity damage

to piers.

1 In 2007, approximately $350 for a 200m2 house.


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Building Codes

The Building Code of Australia is a

performance based code that sets out

the objectives and outcomes required for

different classes of buildings. Acceptable

building solutions (also called deemed to

satisfy provisions) are listed to show how

to achieve these requirements. However,

a builder may choose other construction

materials and practices provided it can be

demonstrated that all the required outcomes

of the BCA are met.

The Damp and Weatherproofing provisions

require the following:

F2.2.2 A building is to be constructed

to provide resistance to moisture from

the outside and moisture rising from the

ground.

P2.2.3 a) Moisture from the ground must

be prevented from causing

(i) unhealthy or dangerous conditions, or

loss of amenity for occupants; and

(ii) undue dampness or deterioration of

building elements.

And NSW adds

(b) Barriers installed beneath slab on

ground construction for the purposes

of (a) must have a high resistance to

damage during constructionThe Australian Building Code Board has

been reviewing the issue of urban salinity/

salt attack for a number of years. One of the

outcomes of this process may be to improve

the clarity of these performance requirements

by including a reference to salt as well as

water. Another may be modification of the

deemed to satisfy provisions.

In NSW, the Building Code of Australiabecomes legislation through theEnvironmental Planning and Assessment

Act. The Building Systems Unit within theDepartment of Planning, consults with theNSW construction industry and stakeholdersvia the Building Regulation Advisory Councilto consider national proposals in terms oftheir suitability for NSW. The State variationto the BCA implemented in 2004 and stillcurrent today, relating to use of highimpact damp proof membranes underhouse slabs was introduced as an interim

measure while national debate regardingsalt attack continues.

On an individual house lot scale, a numberof construction and maintenance decisionsaffect the potential for water movement andthe related salinity damage. These include:

whether to cut or fill the site

whether the ground is reshaped to slopeaway from the building

how the site is landscaped

how the landscaping is watered

how much of the site is hard surfaces vspervious surfaces

whether a path is provided around the

perimeter of the house and sloping awayfrom the building

what stormwater drainage is provided

whether pools, taps, and downpipes areregularly checked for leaks

A builder does not have control over manyof these factors so needs to design andconstruct for the most likely scenario andthe salinity risk of the area.

In this town during wetter periods, the water table is close tothe surface and evaporates, leaving behind an accumulationof salts. During periods of below average rainfall and wateruse restrictions the water table is several metres belowground. Building design and construction should take intoaccount these longer term changes.

Over-irrigation can lead to rises in the water table.

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Trainers manual, trainers video, powerpoint presentationand participants notebook available from the Department ofEnvironment and Climate Change.

In NSW, local government may alsointroduce building policies above andbeyond the BCA although they cannotwater down or make any BCA provisionsnot apply. Several councils have or arecurrently reviewing the necessity of thisoption for building in saline environments.The existing NSW local government policiesgenerally require:

50mm of sand under the building slab

32MPa concrete

seven days curing time for concrete

and reinforce the NSW BCA requirementof a high impact resistant damp proofmembrane

References to urban salinity are also being

made in Council Engineering Guidelines andone council is considering the introductionof a higher minimum construction standardfor domestic pools. Leakage from pools notonly wastes water but adds to the salinitypotential of the area.

The NSW Office of Fair Trading requires allbuilders and tradesperson who undertakework in the home building industry (for

jobs over $1000 including labour andmaterials) to be licensed. License holders

must regularly update their knowledgeby undertaking continuing professionaldevelopment. Sydney MetropolitanCatchment Management Authority, theDepartment of Environment and ClimateChange, and TAFE NSW have developeda four hour course for builders, buildinginspectors and certifiers to increase theirawareness and understanding of urbansalinity and its management. The course iscalled Building in a Saline Environment

An Awareness Course for NSW.


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AS 2870 Residential Slabs and Footings(1996) requires:

a design life of 50 years (clause 1.4.2)

drainage to be designed and constructedto avoid the ponding of water againstor near footings. A graded fall of 50mmminimum away from the footing over adistance of 1m is required even on the

ground uphill from the slab on cut and fillsites ( clause 5.2.1)

40mm cover to reinforcement

concrete to be vibrated and cured for atleast three days in known salt damp areas(clause 6.4.8)

careful detailing of DPC in high salt dampareas (clause 5.3.4)

damp proof membranes to be extendedunder the edge beam to ground level(clause 5.3.3.3)

It also provides an advisory note to use dampproof membranes in South Australia andareas prone to rising damp and salt attack(clause 5.3.2).

A new version of this Standard will bereleased in 2008. Within the durabilitysection, the draft includes specific referencesto saline soils. These are based on theCement, Concretes and Aggregates Australia

2005 publication Guide to Residential Slabsand Footings in Saline Environments. Soilelectrical conductivity measurements areused to determine the concrete strength,cover to reinforcing and curing requirements.Guidance is not given on how to takerepresentative samples, how to managedifferent types of salts, or management ofchanges in salt levels over time.

Australian Standards

Australian Standards are created by groupsof interested stakeholders donating their timeand expertise to follow a prescribed processand format to create a reference document.The BCA deemed to satisfy provisions refersto over 100 Standards thus these standards

become part of the legislative frameworkof the building industry. Several providerequirements for construction in saline soils.

AS 2159 Piling Design and Installation(1995)provides table (6.1) ExposureClassification for Concrete Piles. Soilconditions are listed as non-aggressive, mild,moderate, severe or very severe, based ontest results for pH, chlorides, sulphates andsoil resistivity, for permeable soils whichare below the groundwater table and forlow permeability soils or all soils abovethe groundwater table. Various notes ofcaution are attached to the table such asthe impact of magnesium or ammoniumions, in the presence of sulphates, increasesthe aggressiveness of the soil on concrete.This standard also recommends site specificdesign of concrete for sulphate attacknoting that dense, well compacted, lowpermeable concrete of the correct type ismore important than a high characteristic

strength. Extracts from this standard areprovided in the Local Government SalinityInitiative booklet: Site Investigations forUrban Salinity.

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This series of photos taken approximately seven yearsapart shows how salt levels and salinity indicators canchange with time.

AS 3600 Concrete Structures (2001) alsoincludes a detailed section on durabilityconsiderations. Concrete strength, cover overreinforcing and curing times are specifiedfor several environmental classifications.The description of mild environmentsincludes those where the concrete is in nonaggressive soils or protected by a dampproof membrane. Aggressive soils include

permeable soils with a pH < 4.0, or withground water containing more than 1 gramper litre of sulphate ions. Salt-rich soils inarid areas should be considered as exposureclassification C. This Standard is also underreview and one of the issues to be addressedis saline soils in order to provide moreguidance to designers.

Some of the construction and product

standards have provisions allowingmodification based on experience withthe product. It is therefore important thatmembers of the design and constructionindustry become more aware of urbansalinity processes, impacts and the long termfluctuating nature of the issue.

Traditionally salinity has been addressedby natural resource managers and primaryproducers. Information on the dynamicnature of salinity and widespread potential

for occurrence, or the impact of urban landuse is therefore not always widely availableto the building or construction industry.While natural resource managers may not beaware of trends in the construction industrytowards more salinity sensitive buildingmaterials and practices, or the difficulties infully investigating deteriorating structures 5,10, or 15 years post construction.


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Booklet 6 Building in a Saline Environment

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