Critical Assessment Of Residential Building Compliance With Building Code Of Australia (BCA)

Assessment Outcomes as per Appropriate Codes and Standards

Question:

Discuss About The Australian Buidling Codes And Standards?

The work presented hereinafter dwells on the critical assessment aspects of the residential building whose technical details have been provided to peruse and assess it against the set standards namely: Building Code of Australia part 2 (BCA, 1996). Notably, the report pursues various elements in the house against the given provisions to ascertain full compliance hence such terms as “deem-to-satisfy” will be used accordingly in this context. business, calculations will also be done and results presented in a manner that is understandable and in sync with the sectional provisions. Hence the let the assessment work begin. 

This section presents the various assessment outcomes vis-à-vis the appropriate codes and standards. Hence the following are presented for further perusal:

• A complete full design check against the National  Construction Code, Building Code of Australia Volume 2 for all parts.

The NCA provides the general provisions for legal requirements in the building sector. The BCA document is therefore a universal paraphernalia that envisages harmony in building construction designs and development while ensuring public safety and wellbeing are guaranteed in the developments.

This part, therefore, provides a concrete assessment of the identified elements as per the building code of Australia (BCA).

For this part, table 1 gives the summary of the actual assessment and the specific recommendations thereafter. It should be noted that full compliance includes the conditional status of the surrounding hence issues like soil condition and natural phenomena like earthquakes are included.

• A complete waffle pod slab design as shown on the attached plans detailing and confirming the slab thicknesses and reinforcement (top and bottom) using AS 2870.

Firstly, need to check the wind classification for the area (as provided by local authorities); let it be fixed at N2 hence the following information can be retrieved (as per 1684: 2 (2010):

Gust wind speed for:

Permissible stress = 33m/s

Serviceability limit state=26m/s

Ultimate limit state Vu= 40m/s

Hence for the purpose of assessment, we shall use the maximum value for the design check, that is: 40m/s

For this windy condition and in order to guarantee safe design of the structure, the values of geometric parameters are checked against the maximum theoretical values hence:

Parameter	Theoretical Limit Max.	Actual	Remarks
Height	3000mm	2100	Passed
Width	16.8m	13.8m	Passed
Roof pitch	350	250	Passed
Bracing space	9000mm	7600mm	Passed
Roof type	Hip, gable, skillion, cathedral, trussed or pitched	Trussed	Passed

Forces on the building are determined based on the conditions below:

• Racking-wall deforms
• Overturning wall-due to rotation
• Tendency of sliding
• Connection failure due to uplift

Hence the appropriate timber dimensions must be selected from the tables below for both upper and lower reinforcement:

Reinforcement bars: Number for the top portion:

Stem width	Top steel	Remark
110-150	0
151-220	1
221-330	2	Yes
331-440	3

Beam base width	Bottom steel #	Remark
110-150	1
151-220	2
221-330	3
331-440	4	Yes

• Complete an alternative timber floor design using a conventional bearer and floor joist construction method in lieu of the (as shown) large spanning timber laminated floor joists. Note: The span and spacing for both bearers and floor joists are included (to enable our resident estimator to price) .

	Span	Spacing
Bearer	2800mm	2100mm
Floor Joist	1800mm	1800mm

Now, ensure the new design conforms to the following:

Floor joist: 238mmx38mm with a timber class type MGP 12

Maximum spacing shall be 450mm between centers; this shall be the maximum span.

Notably, designer is at liberty to choose the dimensions that fit the given requirements but should be within the mentioned limits. Timber quality is also a key parameter in the design (Blanchi & Leonard, 2008). This should be selected based on the factors such as level of termite attack, environmental and climatic factors such as rainfall. However, in a nutshell, economics the area is rated as less prone to termite attack, the timber selected should be above reproach. This again is left to the designer to decide the best quality of timber based on the design requirements (Western Australian Planning Commission, 2010).

• Check on all timber designs to ensure compliance with AS 1684, including the following;

• Determination of all timber lintels above openings as shown on plans.

Timber Lintels #	Sizes (mm)
1	400
1	400
1	400
1	400
1	400

Summary of Actual Assessment and Recommendations

Designation	Normative size mm (width)
Roof battens	42
Ceiling battens	45
Top and bottom plates	67
Wall studs and studs at sides of openings	87
Lintels above openings	400mm

Footing system design:

The site class and type of construction: Masonry veneer

Piecewise width of the footing- 6m max

Hence from fig 3.6 (AS 2870) the footing system is established: D=300, B= 300, Ds= 400; Reinforcement type: -3-8 TM

For raft design, the following parameters are checked:

Parameter	Range	Actual	Remark
Ys	10-70mm	35mm	Passed
Max differential movement	5-50mm	25mm	Passed
Beam spacing	<1.25mm	0.97mm	Passed
Beam depth	250-1000mm	900mm	Passed
Minimum depth	>0.7 max	0.7	Passed
Beam width	110-400mm	115mm	Passed
Average load	to 15kPa	8kPa	Passed
Edge line load	to 15kNm	9kPa	Passed

To resist both horizontal and supply some of the loads to the building foundation, permanent bracing is recommended as per AS 1684. Subfloor structure be adequately braced. Allow maximum height of stumps above ground at 1200mm. There should full perimeter masonry base and outer wall construction. Brace size 70x35mm for 2100mm length.

Hence, in the bracing plan, the following are to be implemented:

Determining the wind classification: As per the assessment above, the wind classification is fixed at N2, the roof pitch is 25^o

Next, we determine the wind pressure that will be acting on the building. Consider halving the building at its symmetrical axis relative to the main wind direction throughout the year

Repeat this for various orientation of the building so that the maximum value is used for purpose of structural design especially against racking forces

Next, we determine the projected area of the portion that will be impacted with the wind. Hence dimensions of the building like overall length, width and height of the building are retrieved

Therefore, the racking force is determined from the formula:

Racking force= Projected area of elevation (from various orientations) x Wind pressure

And therefore, the forces can be summed to get the total racking force, to be used for purpose of establishing the required bracing system.

However, it is worth noting that the bracing can be expensive to implement in all orientation, therefore, we select the major orientations (at least two) that will greatly be impacted by the wind strength and hence compromise on the structural integrity of the building.

Subfloor bracing in either north, south, east or west elevations should be considered. Recall that bracing not done in other orientation may slightly make it weaker in that direction.

Additionally, include both top and bottom wall bracing. The top wall bracing must be done up to the ceiling level while in the bottom bracing, fix it at the floor frame or in the case of concrete, at the concrete slab.

ASSESSED ELEMENT/BUILDING SERVICE	PROVISIONS AS PER SECTIONAL CODE/STANDARD	ACTUAL ASSESSMENT	REMARKS
Earth works-excavation	As per the topographical situation and nearby buildings; safe maneuvering needed for zero damages and accidents	Assumed to have been determined prior to as per soil test reports (File No: 48380)	Necessary amendments to be made if need arises
Drainage	Proper with gently sloping land and storm water must comply with AS 3500	Satisfactory; actual provisions to control storm water drainage are to be implemented (as per the given plan)	PVC storm water drain to be constructed to direct to point of discharge
Termite attack management	Not considered	N/a	Not applicable in this case
Footings and slabs	Footings need not be affected by the nearby root trees extension	To be affected by trees surrounding the area	Need to exhaust an alternative solution to the problem (including removal of trees nearby
Concrete & reinforcing	Compliance with AS 3600 for concrete and the reinforcing materials must meet the minimum conditions set in AS 2870	The reinforcing bar tested and full compliance of steel material confirmed. Design calculations were done to check on the structural integrity of the concrete and reinforcing bars/ for size selection of the bars to use, refer to table 3.2.3.2 on the BCA reference	Satisfactory performance as far as design drawings are concerned
Slab construction
Masonry-wall construction	Build with fire resistant material	Masonry wall has greater fire resistance hence material selection appropriate
Framing-steel and Timber
Wall cladding
Glazing
Fire safety	Bush fire protection mechanism be integrated in the design	Brick walls and cladding are fire resistant hence boost in fire safety	Full compliance attained
Smoke alarms	Provisions be included in the plan	Confirmed in the plans
Heating appliances	Operate with minimum effects on the immediate surrounding	Efficiency not yet checked	Provisions to ascertain their efficiency must be included in the designs
Wet area amenities	Designed for convenience and proximal consideration	Checked and realized full compliance
Movement and access	Be straight forward approach with minimum number of corners; also ensure access routes are well defined in the plan	Presence of verandah, corners and stairs is sufficient
OTHERS -Wind areas and Earth quakes	Check the geologist report on the location	Area seems to be less prone to earthquakes; windy conditions expected. However, building structural design integrity will resist the external forces due to the windy conditions and earth tremors	Need to provide analysis report on the impact of these external conditions on the building.

The building design plans attached have been perused and determined that almost all areas of the building design have complied with the minimum provisional codes and standards. Expectedly, a number of areas have been identified for further improvement so as to achieve full compliance. For instance, in the design of footings and slabs, the surrounding area need to be free of trees as the roots would cause irreparable damage to the footings once the building is established. In this regard, therefore, based on the above assessment, a score of 75% can be awarded. Besides, sustainable building construction principles must be integrated as a way to harmonize the relationship of the building with its surrounding. The occupants’ wellbeing must be seen to be supported by the design. Notably, other building codes such as BREEAM need to be adopted and reconciled within the general building construction codes such as BCA. In fact, in the area of energy use, design of the services that provide the building energy must be in tandem with the green energy civil engineering. Energy efficiency measures should be developed, implemented and reviewed on a regular basis (Australian Standard, 2009).

Conclusion

This assessment report provides a competent interrogation of the single dwelling residential building. This is done as per the obligatory building codes and standards. After a careful study of the given house plans and drawings, the assessor matched the elements with the sectional provisions to ascertain either full or partial compliance. In some cases, compliance was beyond reproach; however, as mentioned earlier, there is need to make some amendments in the designs pursuant to the sectional provisions in the relevantly selected codes and standards. Therefore, with some degree of certainty, the building design drawings and plans can be pronounced as “possessing irreducible minimum compliance status”

References

Australian Standard 3959. (2009). Construction of Buildings in Bushfire-prone areas. Council of Standards.

BCA. (1996). Building Code of Australia. Council of Standards.

BCA. (1996). Building Code of Australia: Class 1 and Class 10 Buildings Housing Provisions. accounting AST.

Blanchi, R & Leonard, J. (2008) Property Safety – judging structural safety. In ‘Community Bushfire Safety’. (J. Handmer, eds) CSIRO Publishing, Melbourne

Cheney P & Sullivan A. (2008). Grassfires, fuel, weather and fire behaviour – second edition. CSIRO Publishing Collingwood, Australia

Environmental Resources Management Australia (2000) Baldivis Tramway Reserve Management Plan – Final Report for the City of Rockingham.

RFS. (2012). Plans and Spaces for bush fire Construction. Available at: https://www.rfs.nsw.gov.au/__data/assets/pdf_file/0020/4691/Hunter-BFRMP.pdf

Standards Australia (2009) Australian Standard (AS 3959-2009) Construction of buildings in bushfire-prone areas.

TAS. (2010). Bush Fire hazard management. Available at:  https://www.fire.tas.gov.au/userfiles/tym/file/131392_Building_for_Bushfires_web.pdf

TAS. (2017). Planning. Advisory Note 20 Guidance on the Code and how to determine Bushfire-Prone Areas is available at: https://www.planning.tas.gov.au/library_and_ information/planning_advisory_notes

The Bushfire-Prone Areas Code Planning Directive No. 5.  Available at: https://www.planning.tas.gov.au

Website 2010. (https://www.bom.gov.au/climate/averages/tables/cw_009194.shtml)

Western Australian Planning Commission (WAPC), Department of Planning and Fire and management Services Authority of Western Australia (FESA) (2010) Planning for Bush Fire Protection guidelines – edition 2. Published by WAPC & FESA