NSW Owner Builder Course Tips and Tricks

Basic building material information for NSW owner builders

• Timber.

Timber is sold per metre in increments of 0.3m traditionally (1 foot in imperial units), e.g. 2.4m (8 feet), 2.7m (9 feet), 3.0m (10 feet), 3.3m (11 feet), 3.6m (12 feet) up to lengths of about 6.0m for most timber species. Most local timber outlets will probably only have a few length variations in stock due to the fact that they purchase timber in packs from their wholesaler. Some timber species are sold in 0.6m (2 feet) increments, e.g. radiata pine and oregon.

Timber sectional size is specified as ‘width x thickness’, e.g. a typical order for 12 rough sawn hardwood floor joists that are each 4.2m long with a nominal sectional size of 100mm x 50mm would be ‘100 x 50 sawn hwd – 12 / 4.2’. The 'nominal' size refers to the approximate sawn size of the timber. It is not the finished size.

Wood that has been converted into timber for building purposes will contain moisture and is termed 'green' timber. The moisture will eventually dry out naturally in time (by air seasoning) or the drying process can be speeded up by using a kiln (mechanical seasoning / kiln dried). Green (unseasoned) timber will often shrink in sectional size and twist after installation, particularly green hardwoods (sometimes shrinkage may be up to 10%). Kiln dried timbers (termed ‘KD’) are generally more stable than green timbers. KD hardwood is typically used for major support members in conjunction with radiata pine for wall frames and roof trusses.

Timber may be preservative treated against wood decay and termite infestation. Treated timbers often have a greenish / bluish colour. Treatment is carried out in varying grades depending upon the hazard exposure level. They are termed (e.g.) H2, H3, H4 - the higher the number, the higher the exposure resistance.

The most commonly used timber species for building purposes today is (radiata) pine. It is widely used for items ranging from structural wall framing members and roof trusses to flooring, timber wall and ceiling linings, door jambs, window reveals, skirtings and architraves. It is also used in the manufacture of building boards used for e.g. sheet flooring, cupboard manufacture, doors etc. Pine is a desirable timber for building purposes because it is light weight, easily worked, relatively cheap compared to other timber species and adaptable to many applications. Pine is a plantation grown timber species that is seasoned (dried), gauged (consistent in sectional size) and stress graded (rated for strength e.g. MGP10 and MGP12). F timber grading (e.g.) F5, F8, F11, F27 etc refer to the strength of the timber - the higher the number, the greater the strength of the timber.

• Brickwork.

Bricks are priced per 1,000 and sold by the pallet due to handling and transporting requirements. Pallet sizes vary from supplier to supplier from about 380 to up to about 500 depending upon the method of packaging for transporting. For estimation purposes, there are about 50 bricks per m2 for each skin of brickwork in a wall. 1,000 bricks will cover a wall area of approximately 20m2 per skin of brickwork.

Mortar used in brickwork comprises cement, sand, hydrated lime (generally), a plasticiser (often) and clean water. The amount of each component will vary from Brickie to Brickie and from job to job. Brickies (bricklayers) have material preferences and they will generally tell the owner-builder what they require.

Cement is sold in bags (traditionally 40kg bags but now in 20kg bags). Lime is sold in 25 kg bags. Sand is sold by the m3 or by the tonne. Plasticisers (Bicol) are used in the mix to improve the mortar quality for laying purposes. Sometimes off white cement and mortar coloring (oxide) will also be used. For basic estimation purposes, to lay 1,000 bricks, there are about 6 x 20kg bags of cement, 3 x 25kg bags of lime and about 1m3 of sand depending on the size of the holes in the bricks and the mortar strength required.

The owner-builder will generally be required to provide the bricks and mortar components. Brickies typically provide their labour only and work in a team (a small team would be 3 brickies and a labourer). They generally quote their laying fee on a per 1,000 brick basis, e.g. a brickie may quote (say) $900 per 1,000. Special bricklaying, e.g. arches, columns, chimneys etc, are typically quoted on an hourly rate basis. Bricklaying rates will vary considerably depending on the work available. Items like scaffolding and brick saw hire costs are typically paid by the owner-builder.

• Concrete.

Concrete is sold per m3 in increments of 0.2m3, eg 3.6m3, 3.8m3, 4.0m3, 4.2m3, 4.4m3 etc and is priced per m3 of the full truck load. Broken loads of less than 3.0m3 are usually more expensive per m3 due to transporting costs as the whole truck is required to deliver only a part load. Concrete prices will vary considerably from depot to depot depending upon what raw materials are available locally and supplier competition.

(more information in our NSW owner builder course training manual)

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Estimating construction costs

Establishing the final cost of the project is a major problem for owner-builders. Even a relatively small 5% estimating error in a $200,000 project will result in a $10,000 discrepancy. With this in mind, the owner-builder should consider using the services of an industry professional, e.g. construction estimator, quantity surveyor, professional builder or an architect / architectural draftsman, to help determine the approximate cost of the project. It must be remembered that an estimate is simply an educated prediction of the possible cost of the work at the time it was prepared. An estimate cannot allow for all of the many variables that can occur during construction therefore the estimated cost should be monitored and the budget updated periodically to ensure that the final cost of the project does not exceed the amount of funds available.

Unforeseeable issues like material and labour price rises, material theft, incorrect material purchases and material damage replacement can cause budget problems. Another problem that may be encountered by the owner-builder is not allowing for items that are not actually shown on the plans but are required to carry out the work, e.g. scaffolding, crane hire, concrete pump hire and concealed underground items like rock foundations and drainage connection problems. Any extended work time frame will also result in cost increases.

The boom / bust situation that frequently occurs in the building industry will also affect the overall cost of the project. In boom times, builders with lots of work generally quote high. This may influence a person to do their own building work under an owner-builder permit/licence. Unfortunately in boom times trade contractors also have higher charge out rates and often don’t want to work for owner-builders because they have other work available to them from their regular builders.

Estimating the cost of the project for design, financing and budget purposes initially involves coming up with an indicative, preliminary construction cost that is based upon a m2 rate taken from the floor plan, e.g. 200m2 x $750 per m2 = $150,000. The calculated figure will provide a rough guide to allow the owner-builder to 'ball park' the construction cost. The estimated m2 based cost must be adjusted to allow for the many variables associated with the project and site specifics. The architect / architectural draftsman who will prepare the working drawings and specification will be able to provide assistance with the preparation of a more accurate construction cost estimate. Note - the $750 per m2 figure is provided as a course example only and must not be relied upon for estimating purposes.

Much of the work involved in estimating building costs is associated with obtaining quotations for the supply and fix items, e.g. tiled roof covering, plasterboard linings etc, determining the cost of the materials required for the work to be carried out by labour only contractors, e.g. bricklayers, and materials costs associated with work that will be personally undertaken by the owner-builder. The owner-builder must also allow for pre-construction costs to cover such items as obtaining development consent, preparation of the plans, insurances, engineering fees, lender fees and site establishment costs. You can spend many thousands of dollars before the actual building work commences.

The quantity of materials to be ordered will be based upon the actual materials required for the job plus an allowance for wastage. The waste allowance is often difficult to establish and will vary from job to job, eg how much extra concrete will need to be allowed for wastage and irregularities in footing trenches? Builders are able to approximate waste allowances based upon their experience. The owner-builder will not have the benefit of such experience.

The waste allowance is generally expressed as a percentage of the actual materials required, e.g. 5%, 10% etc, and will vary according to the material being used, the location of the project and the size of the project. Allowing too much waste will result in materials being left over and possibly wasted (you may not be able to return some items). Too little allowance for waste may result in colour and size variations in the materials and will also cause time delays, incur more transport expense and require trade contractors to return to the job.

(more information in our NSW owner builder course training manual)

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Construction planning

A professional builder will spend many years gaining educational qualifications and practical training to allow them to carry out building work. The owner-builder will not be armed with the same skills yet he/she will need to have a reasonable understanding of the building process to successfully owner-builder. The owner-builder may find that following the progress of a dwelling under construction will assist in understanding the basic principles of construction sequencing.

The following is a basic sequence that could be used to illustrate the construction of a single storey dwelling. The example provided is a typical project style dwelling with a tiled roof, brick veneer external walls, concrete slab on ground floor system and aluminium windows.

The sequence lists the main stages and is provided as a basic guide (only) as there are many intermediate stages that will need to be included within the sequence. No management items have been included eg arrange development consent, insurances etc. Adjustments will also need to be made to suit the many variables associated with the site, building specifics, availability of labour, availability of materials and prevailing weather conditions. Some activities may overlap whilst others can be completed out of sequence if they are not dependent upon completion of other activities.

The building industry uses the terms ‘Floor level’, ‘Lock-up’ and ‘Practical completion’ to describe particular stages of construction. These stages have been indicated in the sequence in upper case.

• Site establishment – e.g. provide temporary services (water and power), toilet, site shed, site access road, sediment control fences, perimeter public protection fencing, site signage, locate position of existing underground services.
• Clear, cut and fill the site – e.g. backhoe or small excavator to alter the profile of the site to accommodate the dwelling.
• Set out – e.g. surveyor to set out the dwelling.
• Sewer drainage rough in – e.g. plumber / drainer to install the under slab sewer drainage pipes.
• Termite treatment – e.g. pest inspector to apply the chemical spray under the slab.
• Concrete floor slab – e.g. form worker / concreter to install the formwork, steel reinforcement, place and finish the concrete slab.

FLOOR LEVEL STAGE

• Wall frame – e.g. carpenter to erect the wall frames.
• Roof frame – e.g. carpenter to erect the roof trusses.

(more information in our NSW owner builder course training manual)

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Working drawings and specifications

The Council will require submission of working drawings and specifications to describe the work intended to be carried out. The working drawings are referred to in the building industry as the ‘plans’. The ‘specs’ (specification) is the written material used to complement the working drawings and provides details of the materials used and reference to the BCA and applicable Australian Standards.

The working drawings may be prepared by an architect, draftsman, builder or the owner-builder may choose to prepare them personally if he/she has the necessary skills. The working drawings should be prepared in an industry acceptable format to assist interpretation. Most suppliers and trade contractors prefer to use professionally prepared working drawings as there will generally be fewer errors associated with misunderstandings and inadequate detail.

The architect / draftsman may produce their own specification or use a standard proforma type specification. Standard specifications are available from industry groups such as the MBA (Master Builders Association).

The working drawings must be drawn to scale (generally 1:100 for floor plan and elevations) and be presented in fashion acceptable to the Council. Some Councils will only accept professionally prepared working drawings.

The working drawings and specification should contain enough detail to allow trade contractors and suppliers to quote and carry out work accurately. Drawings that don’t have enough detail may result in the owner-builder not getting what they think they have paid for and may also result in the owner-builder having to pay for costly variations. Costly disputes with trade contractors over variations are not uncommon.

(more information in our NSW owner builder course training manual)

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BASIX (the building sustainability index).

Since 1997 the State Government in NSW has encouraged Councils to implement energy savings for all new dwellings. BASIX Certificates became mandatory for all new dwellings in Sydney on 1/7/04. On 1/7/05 this was extended to cover all new dwellings in NSW.

On 1/10/06 BASIX was introduced for alterations and additions to existing dwellings where the estimated construction cost of the work exceeded $100,000 and also for swimming pools. On 1/7/07 this was extended to cover alterations and additions where the estimated construction cost of the work exceeded $50,000 where Development Approval is required and also for swimming pools of 40,000 litres capacity or more.

BASIX Certificates must be project specific and provide commitments in relation to saving water, thermal comfort and greenhouse gas reduction. A BASIX assessment involves an appraisal of such items as orientation of the living areas, thermal mass of wall and floor construction components, windows, glazing, shading devices, hot water unit type, rated tapware and shower heads, collection and use of rain water, thermal insulation of ceilings and walls, lighting, exterior colour schemes, pool covers and pumps, etc. to produce dwellings that are more comfortable to live in and cost less to run. A compliant BASIX Certificate must be provided before a Construction certificate can be issued. Changes made to a dwelling's plans after Development Approval may require a new BASIX Certificate to be produced to satisfy Council and Department of Planning requirements.

There are two ways to obtain a BASIX Certificate.

1. Engage an Accredited ABSA Assessor.
2. Carry out a Do-It-Yourself (DIY) assessment.

(more information in our NSW owner builder course training manual)

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Inspection of the work during construction

Mandatory inspections of the building during the construction stage by the principal certifying authority (PCA) is a condition of development consent. Council will provide a generic inspection list and the PCA will nominate at what stages the work will be inspected. The owner-builder will be required to arrange the inspections with the PCA, providing prior notice of up to 2 working days.

The mandatory inspections typically undertaken by the PCA for a dwelling include

• Assessment of footing trenches with the steel reinforcement in place prior to the placement of the concrete.
• Assessment of concrete slab areas with the steel reinforcement in place prior to the placement of the concrete, e.g. floor slabs, veranda slabs and concrete walls.
• Assessment of the framework of any floor, wall, roof or other building element before wall and ceiling linings are installed.
• Assessment of the waterproofing in wet areas, e.g. bathroom, laundry, ensuite and toilet.
• Assessment of the stormwater drainage connections before backfilling.
• Assessment of the building when it has been completed and prior to any Final Occupation Certificate being issued.

(more information in our NSW owner builder course training manual)

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Termite risk management

The risk to buildings associated with termite damage in Australia varies considerably from location to location. Some areas have extreme termite problems, e.g. parts of the Northern Territory, whilst the risk to some other areas may be considered minimal, e.g. Tasmania.

The termites that are primarily associated with causing damage to dwellings live in the ground (subterranean termites). Termites essentially eat wood based materials but they will also eat many other materials when wood is not available or when the termites try to get to wooden materials.

Timber framed structures in coastal and rural areas of NSW are particularly at risk of termite infestation due to the amount of uncleared and partially cleared areas. However, there is still a significant risk of termite infestation in urban areas. Some people think that because they have a steel framed dwelling they won't have any termite problems but, because the building contains wood products, e.g. skirtings, architraves, doors, paper on plasterboard lining sheets, cupboard materials etc they are still at risk.

Subterranean termites require darkness, a food source (wood), moisture, ground contact and contact with their nest. Timber framed dwellings are ideal locations for termites and the owner-builder must ensure that they do not create situations that attract termites. This includes ensuring that the subfloor and area adjacent to the perimeter of the building are dry, that the edges of concrete floor slabs are exposed for periodical inspections, that food sources like bark chips are not placed against the building’s external walls, that timber off cuts in the subfloor area are removed and that elevated subfloor areas are dry and easily accessible for periodical visual inspections. A professional timber pest inspector will be able to provide more advice in this regard.

The Building Code of Australia (BCA) requires that if the dwelling is located in a termite risk area and if the primary building elements in the dwelling are subject to termite attack, e.g. wood, an appropriate termite barrier must be provided. The termite barrier must conform to Australian Standards and a durable notice be permanently fixed in a prominent location, such as the electrical meter box, providing details of the method of termite protection used, the date that the system was installed, the life expectancy of any chemical used (if applicable), the frequency of future inspections and the installer’s details.

(more information in our NSW owner builder course training manual)

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