Timber Framing

In the first section of this assignment, I will be required to provide an extensive analysis of the different types of roof members, which exist within conventional roofing. The section will also entail a description that will expound on the process used in attaching the roof items to the top plate as required by the construction law in Australia. The second section of the assignment will involve writing a report on the approach taken in determining sizes of the roof members. In the third part of the assignment, I will describe the implications, which result from the center to center spacing of the rafters and ceiling joists on the roof and the ceiling battens. In the fourth section, I will provide a description that will take to expound on the different types of the items, which will be significant in building the trussed type of roofing.

Moving forward with the assignment, I will be required to determine the structural members, which are required for the purpose of timber framing of the dwelling only. Finally, on the provided floor plan, I will indicate the various positions of all bricks or timber piers, bearers and floor joists for the purpose of suiting the specified timber flooring system and I will perform this task by way of nominating the timber floor systems provided.

Part 1: According to Certificate IV Building and Construction Module 6(26-34), there are many types of roof members, which are determined or rather classified according to the pitches and styles used in constructing them. A hip roof refers to a structure believed to be widely used in its traditional form. It possesses the advantage of erecting both the single height walls and the permanent channel. Belcote roof refers to a hip-type of roofing structure, which possesses a verandah, shallower in pitch than its resultant main roof. The Gable roof refers to the roofing system, which requires its end to be dressed properly in order to avoid its immediate collapse.

The hip and valley roof refers to a roofing structure with the advantage of single height walls and is further cut away in one of its corners to form a valley that allows for shaping the resultant blocks. A boxed gable roofing structure refers to an extended gable roof so that its wall line is strategically placed beyond the normal walls. A skillion roof is a type of roofing structure whereby the main part of the house is gabled, while its rear end presents an inclination, which leans steadily onto it. In a broken hip and valley kind of roofing, the separate wings stretch beyond one another so that in the long run they will be placed at different widths altogether.

A Dutch gable roof refers to a roof bearing the characteristics of the hip, Belcote and gable type of roofing structures. A jerkin head roof is made up of the combination resulting from the gable roof with a hip, inclined on a single side of the apex. It is usually structured in such a way that its inclination is used in place of garret. A flat roof is the most common roofing system, which is usually used in the construction of multi residence structures. It is structured at a flat pitch of less than 3 degrees. Clerestory roof refers to a roofing structure, which combines both the skillion and the gable roof so that a ventilation window is left at the top most height of the main roof. In the rafters roofing system, the rafters are attached to the top plate through a cut, which is usually referred to as the “bird’s mouth cut” (Mutt 45-56).

Part 2: The span sizes determine the range of the roof members in different ways. They are explained as follows: firstly, the sizes are determined when the concentrated load is placed within the central third of the lintel span. This particularly means that the resultant breadth of the jam studs on each side of the provided opening shall in essence be increased by one half of the breadth of the stud required to bear the aforementioned load. Secondly, the sizes are determined where the concerted load is placed within one third of the lintel span from the jamb stud. The resultant jamb stud will have to be increased in its size by the ensuing size of the stud supporting the aforementioned load.

Part 3:According to Certificate IV Building and Construction Module 5(13-20), the implications brought about by the center to center spacing of ceiling joists stipulate that the aforementioned spacing should at all times be directed on the same platform as the main rafters. It should be done so that they may be fixed to an act which ties between the lowest points (feet) of pair opposing the rafters. These ceiling joists are required for enhancing the support needed in lining of the ceilings. The end supports of the joists are expected to be in full width of the resultant wall plate.

Rafters on the other hand, are supposed to be sustained by struts at an equivalent numeral of equally spaced intermediate points. In case of an absence of the strutting points, they should then be supported by an underpurlin in a single direction while the valley rafters are to be sustained by the underpurlin in either sides of their direction.

Part 4: Assuming the given layout is the trussed roof, which will be required to build the roof, include common studs whose size determination would depend entirely on the different sizes of the matching studs. The next item, the studs concerned with bearing the concentrated load, which will also be determined by the different span sizes used in both single and upper-storey constructions.

The studs, which are used in supporting the concentrated load, are suitable for coming up with the sizes of the strutting beams, roof struts and girder trusses in general. The other items, in line, are jam studs, which are normally used at the sides of the openings in both single and upper storey buildings altogether. The fourth item in the list refers to the gable or rather skillion end wall studs, which are also established in accordance with the span tables provided. The fifth item refers to the mullions, which are established through the jamb studs of the timber framing code. The next item refers to the bottom plates, which are used in providing support for floor joists, solid blocks existing in between the bearer or the concrete slab at large.

The top plate forms the major item in the making of a trussed roof. The top plates are suitable in locating trusses at any given position along the given length of the plate. The top plates are suitable only when they are at a minimum of 35mm depth, particularly when they load from the roof trusses.

Part 5(Bracing): The determinants of external wind bracing requirements for the building involve both the area of elevation and the racking force. In the area of elevation criteria, the direction of the wind to be put into consideration should be resulting from the greatest load of the length and width. The direction of the wind used is expected to be emerging from the direction of the worst wind in order to maintain a steady area of elevation.

Since the building at hand portrays complexity, its shape is to be considered separately and later added. To simplify the process simple a figure for the total area is established through computations. The calculated bracing will then be used to bring out the worst situation, which will then be distributed throughout the building taking into consideration the forces that are to be relevant to each shape in hand.

The second determinant, racking force, is determined by multiplying the supposed area of elevation of the given building by the lateral wind pressure. The racking force is usually calculated for both directions, that is, for both the long and short sides.

Part 5: There are two structural members, which are required in timber framing. These two structural members are sheet and cross-timber (steel bracing). In sheet braced wall, the sheeting is allowed to spread evenly from the top plate to the subsequent bottom plate taking into consideration that several horizontal sheets are made to join the noggins while on the other hand, the fixing goes for the purpose of containing the requirement stipulated in both the top and the bottom plates altogether. Fact put forward to establishing sheeting requires that the sheet bracing walls be a minimum of 900mm width in order to satisfy the already established stipulations of their nominated ratings (Vicky 5-19). In cross-timber bracing, the sheet is placed at an equidistant position to both the top and bottom plates so that the vertical connecting the noggins are made to join separately. These types of structures are separated completely from the sheet braced type (Vicky 18).

Part 6: Bracing in the timber floor system is evenly distributed with the maximum distance between the piers, bearers and joists under the platform length of the timber floor system. It is evaluated in the following ways. Firstly, for wind classification N1 and N2, 14000mm, provided the minimum width of floor is 4800mm. Secondly, for wind classification N3, 14000mm, provided the minimum width of the resultant floor is 6000mm, and thirdly, for wind classifications N4, 11500mm, provided the minimum width of floor is 6000mm. it is further stipulated that when the width of the floor is less than the above figures then the spacing of bracing will supposed to be determined as provided by the span tables (Muninn 27-36).

Conclusion: The major assumption held when determining the width of the floor stipulates that the aforementioned floor should be evaluated parallel to the direction of the wind under consideration. Both the long and the short sides of the wind are expected to be measured altogether.