Question 1(Using AS1684)
- According to the architectural plans, the maximum width of the building is 8.150 meters. The width falls within the maximum allowable width designated for N2 areas by clause 1.4.5 which is 12m.The recommendation is outlined in clause 1.4.2 which deals with cyclonic and non-cyclonic areas.
- According to the plans, the building can be designed in the area. Clause 1.4.3 states that the building should be of either rectangular, square or L-shapes, or a combination of rectangular elements. From the plan, the building is a combination of 3 rectangular shapes and therefore no restriction.
- Clause 1.4.4 limits the number of storeys to 2 and as such, the building is in a safe position with 0 storeys.So yes, the building can be designed
- The maximum width of the building is 8.150 meters. Therefore, the building falls within the maximum allowable width of 12.0 meters, as stipulated by clause1.4.5.
- The section A-A indicates that the height of the wall can be obtained from 12.450 – 9.750 which equals 2700mm, the maximum height as stipulated by clause 1.4.6.
- Clause 1.4.7 recommends that the maximum rafter overhang should be 750 mm.Acccording to the drawing plans and approximations, the overhang can be estimated by adding 380+250=630.The approximation falls within the required maximum.
- The roof types recommended by clause 1.4.10 are: hip, gable.skillion.cathedral, trussed, pitched or any suitable combination. According to the plans of the building, the most suitable combination, according to the varying ridges and valleys, would be that of a gable, hip and pitched roofs. The cathedral roofing system is suitable for the patio.
According to AS1684, clause 4.1.2, the standards stipulates that the material to be used for the flooring system should be timber regardless of the species. Furthermore, the AS1684 outlines the practice design for timber floors but does not consider concrete anywhere. In line with designing the building, it is not possible to use this standard because the building has a concrete floor.
A class S site refers to a place where the clay is slightly reactive and the ground movements are minimal. As per BCA volume 2-2010 figure 5.2.3(a) and the table, the depth of a site S edge beam for masonry veneer as well as articulated masonry veneer is 300mm.
There are three specifications when it comes to the drainage specifications. BCA 2010 volume 2 clause 184.108.40.206 outlines the height of the slab above the finished ground level in: areas of low intensity rainfall, impermeable surfaces and any other cases. In this scenario, the most appropriate height is 150mm
Fill may have been a necessity during the earth works and this is indicated by sharp gradients as described by the contours. According to BCA volume 2 clause 220.127.116.11, filling may be necessary where: fill is deeper than the existing soil level and for protection of the footing system.Furthermore,fill is necessary for drainage of the area and as such, it cannot be simply overlooked in this case.
Controlled fill refers to material that has been placed and compacted in layers using compaction equipment within a defined moisture range to a defined density while rolled fill refers to material that has been placed in layers and compacted by continuous rolling by an excavator.
kPa is a measurement unit that defines the ability of a material to withstand a force over a specified area. It is used to define bearing pressure which is the strength of the soil and its ability to withstand loads applied through the foundation.
The bearing pressure on which the slab edge beam is to be connected should not be less than 50kPa in natural soils. This is in accordance to clause 18.104.22.168 BCA volume 2
The figure 22.214.171.124 of BCA volume 2-2010 resembles the external detail of the external wall because of the construction methodology employed.Accordinmg to the figures, the foundations is made up of internal and edge beams which are to ensure that the loads from the load bearing walls are distributed appropriately into the ground
A DPC is a membrane that prevents the penetration of water and moisture into a building. The membrane forms a continuous barrier around the building, walls and piers below suspended walls, therefore preventing the ground water from penetrating into the aforementioned elements.
According to BCA volume 2,flashing refers to a strip or sleeve of impervious material dressed, fitted or built-in to provide a barrier to moisture movement, or to divert the travel of moisture, or to cover a joint where water would otherwise penetrate to the interior of a building.
There are a number of instances that may require installation of flashing. Some of the places where flashing is observed include: chimney, roof butting a wall, sill and head flashing, the base of cavity walls
AS1684 table used
Timber stress grade
|Single or continuous
span used for sizing?
(mm x mm)
|Post (note: footing type 2)||3.2||F11||xxxx||1800||xxxx||100100|
Outdoor structures Australia
|Australian Spotted gum||1800||20||xxxx||65 19|
There are four types of walls that use brickwork. Brick veneer, reverse brick veneer, double brick and the solid. The first case involves covering the external wall surface with a bricks while the reverse case involves covering the internal surfaces with bricks. Basically, these are insulation measures and provide the wall surface with an exquisite finish. In Australia, brick veneer has been the widely adopted system for brick walling but the cavity sizes as well as the sizes of openings have been greatly studied and revised in most standards. It has been stated that the walls with the appropriate cavities are very effective in ventilation and drying. As a matter of fact, walls with cavities have the ability to dry three times faster than those without cavities. It is this factor that makes them effective water barriers.
AS 3700:2001 requires that the openings should be about 76mm by breadth with the centers at a maximum of 1200mm.Therefore, the system equates to 633m2 opening area for every meter of brick wall. These standards may also be found in the BCA.
AS1684 provides a platform for the designer to ensure that there is appropriate fixation of nails to both the hardwoods and softwoods. Clause 9.5 details the nominal fixings. In this, the clause tries to indicate the diameters of the nails to be used for the framing of both softwoods and hardwoods. As the clause indicates, there is a minimum requirement for the diameter for the nailing that are machine driven. The diameter for hardwood is 3.05mm while that for softwood is 3.33mm.The difference in diameter arises from the ease as well as the difficulty of penetration. Furthermore, the clause indicates the types as well as the length of nails that will be used in each scenario. However, the designer has to consider the wind classification system into which the building falls. Some nominal fixing of the buildings as per the design are indicated below.
- The nominal fixing requirements from the bottom plate to the slab. The requirements are indicated in table 9.3 and in this, the table indicates that the nails needed have to be 75mm and of the masonry type (hand driven at the edge of the slab).Furthermore, the maximum spacing of screwing and bolting from center to center is 1200mm.
- .C). The nominal fixing requirement from the studs to the bottom plate are specified in table 9.3.however, AS1684.4-2006 does not consider the difference in direction. The standards does not separate the fixing requirements of the studs to the bottom plate and the studs to the top plate. As a general rule, the table indicates the fixing requirements of the plates to the studs. There are two types of plates that are defined by table 9.3:plates up to 38mm thick and plates whose thickness is between 38mm and 50mm.The former plates require 2/75 05mm nails through the plate while the latter require 2/90 3.05mm nails through the plate. Furthermore, 2/75 3.05mm nails may be skewed through the stud and into the plate.
The specific fixing requirements of a building are outlined by AS1638 clause 9.6.1 and detailed in table 9.4.The specific fixing requirements are an addition to the nominal fixing requirements and determined by the roofing system as well as the wind classification.
- To begin with, we need to determine the specific fixing requirements from the bottom plate to the slab. The only requirement is the rafter or truss spanning. In this case, the details given are that the truss span is 7830mm and the fixing are 600mm center to center. Therefore, because there are only four spans offered in table 9.6 (3000, 6000, 9000 and 12000), the span to be employed in the design is that of 9000mm.The fixing requirements are as follows: 30 8mm G.I strap or one framing anchor.
- The second specific fixing requirements pertain the bottom plates to the studs. As in the case of the nominal fixing requirements, the specific fixing requirements do not separate the fixing requirements of the bottom plate to the stud with the fixing requirements of the studs to the top plate. The requirements for the 7830mm rafter span and 600mm center to center fixing are covered under in table 9.4 and are as follows: 30 8mm G.I strap at 1200 mm maximum centers along wall with 3/30 2.8 mm diameter nails to each end of the strap
There are two types of 450mm center to center common studs. The first type is described in AS16784 table A9 and provides the necessary detail on the 70/75mm common stud supporting single storey and the storeys supporting external bearing walls. The second type is described in table A10 and describes the 90/100mm frames that support the single storey bearing walls. Furthermore, they describe the studs supporting upper storey load bearing walls. Therefore, it depends on the location of the studs and basing our argument on the frames which support single storeys the table of use is the A10.Using the 7830 span and the sheet type roofing system, the size of the F5 seasoned timber would be 90 35.it is important to consider that this timber has a maximum notch of 20mm.
Still basing our argument on the sizes offered in table A10, the size of the MGP10 would still be 90 35. This indicates that the size of the MGP10 is very intricate, in this scenario, and that altering the size may have detrimental effects. Therefore, using a smaller size will not suffice the requirements of the studs.
The size will not be sufficient for the western gable end wall studs and proper design will have to be considered prior to the actual construction. As per my opinion, I would suggest the 70 45 F5, unseasoned grade. As per table A19, the timber should have a maximum notching of 20mm and the frame should be 70/75mm.Furthermore, my recommendation is that the average stud height should be 2700mm.
The house elevation for different wind options. As per AS16874 clause 126.96.36.199, the procedure begins by first establishing the wind classification in which the building considered falls. The category determines the bracing system required and the distribution on the walling. There are 6 options available when it comes to building design: S1, S2, S3 and L1, L2 and L3.As per the building, the following are the options presented:
|Wind direction||Number of type A bracing Units required|
The bracing depends on the wind direction and more bracing units are required on the side with the dominant wind direction. As stated before, bracing prevents the building from collapse and in extreme case getting blown away by the wind. In design of timber framed buildings, some of the specifications for bracing have been outlined with the purpose of helping the designer and builder to provide sufficient bracing systems to the building.
|Wind direction||Number of type A bracing Units required|
Bracing is of fundamental importance to any building structure as per the stability requirements .it is in this regard that it cannot be ignored, especially in timber framed structures.AS1864 specifies the different types of bracing to be accorded to the various types of construction as can be illustrated in the table below.However,all this depends on the house location and typically, areas that are more windy require a more elaborate and detailed bracing system that building in areas that are that are more calm. In AS1864, the elevation, construction and the wind classification determines the type of bracing that a building is accorded.
|Type of bracing||Minimum length of wall(with no openings) required for installation|
|Two diagonally opposed pairs of timber
or metal angle braces
|Metal straps – tensioned||1800 mm|
|Timber and metal angle braces||1800mm|
|Diagonal timber wall lining or cladding||2100mm|
|Decorative plywood – nailed||100mm|
In the standards, table 8.3 demonstrates the above aspects of design and furthermore specifies the minimum and maximum lengths required for the bracing system to be effective.
AS1684 provides specifications on the bracing required for buildings. All this is well explained in section 8.
- The span of the ceiling joist should be about 2400mm but in this case, it will be continuous.
- The span of the hanging beam will be 3000.
- Using MGP10 ,and a span of 3000mm,the size of the hanging beam may be 140 35mm
- Considering that the maximum length to be covered by the roof is 14.74m.the roof span may be approximated to be greater than this, therefore, it should be a minimum of 14740mm.
- The rafter span may be taken to be 1800mm, seasoned F5 timber.
- An under purlin is not a requirement since the rafter and all other members ensure that the roof loads are effectively transferred to the joists.
- Providing an under purlin at the midspan, the 70 45 MGP10 rafter would be sufficient.
- The overhang would be 630-450=180mm.All this has been described in calculating the total rafter length.
- The overhang is compatible .AS1684 clause 188.8.131.52.
- The type B bracing units, as per As1684 clause 184.108.40.206 are suitable for the gable end of the roofs
- The bracing requirements of trussed roofs can be obtained from Australian building standards that major on roof construction and design.