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0 INTRODUCTION

The roof is one on top building element. Roof function is to protect the building from
rain, heat, and wind. Sometime, the roof serves as a release of sunlight into the building. It
also constructed so that the heat does not seep out too much through it. In addition, it can add
beauty to the roof of the building. Roof often using reinforced concrete beams, truss plane,
wood, and steel.

The proliferation of the construction industry today, various technologies have been
invented and developed. For example, many steel-based construction technologies researched
and developed. Steel is a lightweight material, able to bear the burden off several times of its
own weight. Furthermore, wood production was controlled to prevent the extinction of the
world's forests are a treasure for a long time. Secondly, a variety of alternative materials
created and released for the choice of building materials. Therefore, the use of steel as a
structural roof trusses to be one of the main alternatives proposed in Malaysia.

Before the construction of the roof, the roof beams need to be built. It is because the
beam is a structural component built horizontally and can load loaded of the roof, walls and
slab. He suffered bending moments, shear forces and deflections. Beams are structural
elements that bear the burden of side like slab. Normally it suffered internal shear and
bending deflection when the load is applied.

Construction Management | 1

meaning a roof supported by steel beams can be much wider or longer than other types of roofs. meaning wood beams will have to be inspected and repaired more often than metal or composite beams. as the material is structurally strong enough to bear weight when supported by stronger beam materials beneath. but some smaller structures may have a peaked roof. whereas wood beams can readily be cut on site. or cracking. and other elements out of the house. but such beams are not designed to carry a significant amount of load. or mold build-up. and other materials now come with a cheaper price tag. The type of roof beam used in a structure depends on the size and shape of the roof. They are also commonly used as flooring. "Roof beam" has become a common term to describe the relatively large wooden beams that support a roof structure (load-bearing). rain. It is. A wood-plastic composite beam will be lightweight and less prone to rotting. A newer type of beam than the more traditional materials. warping. Some homeowners have noticed this term gradually worming its way into their lexicon. Structures that use steel roof beam construction usually have flat roofs. Composite beams are made from more than one material. a roof beam is generally a length of steel. prone to warping. Steel is cheaper than wood in most cases and it can handle a load much better. Steel can hold significant amounts of weight. their homes are the ones that have exposed roof beams projecting out to. Roof beams can also Construction Management | 2 . or cracking under load. Most of the larger structures such as skyscrapers use steel for their roof beam construction. a composite roof beam can be made from several different materials to make the beam lighter and stronger. or beyond. The wood roof beam has been the material of choice throughout history because wood has been readily available and easy to cut for centuries. and how much weight the roof is required to hold.0 ROOF BEAM Based on wiseGEEK. wood. Typically. and it can carry a load across a large area. or aluminum that holds up a roof meant to keep snow. On extremely small structures. however. Wood has become more expensive as time has passed. especially outdoors in the yard. Wood-plastic composites are more commonly used in trim and non-load- bearing structures. warping. composite beams may be used for roofing. the roof edge framing. but steel beams must usually be cut off-site and trucked into a location. rotting.2. with one of the most common combinations being wood and plastic. and less prone to rotting.

Roof beams.0 Example of roof beam. Construction Management | 3 . The rate of decay.be non-load-bearing (ornamental). Even beams that are cut flush with the roof edge are not immune to the effects of wind driven rain and temperature variations. will vary between regions. More often than not. do not support roof structures and in fact are often just suspended from them. These decorative beams. though not necessarily easily distinguishable from load-bearing ones. often the only part of a structure not protected by the roof itself. which is affected primarily by moisture and temperature. The degree of exposure varies with the building design and construction details. roof beams are exposed to the weather. Figure 2. are particularly vulnerable to weather related deterioration.

This broad range of benefits means that they are commonly found a wide range of building types. Such specific guidance is normally based on extensive testing of a given product. The particular advantages and disadvantages of each individual solution are summarized below. and reduce steel erection times. BS EN 1993 or BS EN 1994.2. including flexible. to identify the most appropriate and cost effective solution. For some types of beam this codified guidance is complemented by specific design guidance. 2. Generally long spans result in flexible. column- free internal spaces. Many long span solutions are also well adapted to facilitate the integration of services without increasing the overall floor depth.1. Construction Management | 4 . and often presented in the form of design software. The design of long span steel and (steel-concrete) composite beams is generally carried out in accordance with BS 5950. such as that on the design of beams with large web openings (see SCI P355 ).1.1. or manufacturers' information. and reduced steel erection times.1 Long span beam Spans in excess of 20 m can be achieved (for the purposes of the definition of long span are taken as anything in excess of 12 m).1 Type of Roof Beam 2. reduce substructure costs. so that a designer can assess the benefits offered by a particular solution in relation to the drivers for a given project. reduced foundation costs. column-free internal spaces.1 Design of long span beams The use of long span beams results in a range of benefits.

The aim is to present a wide range of solutions.1. which offers considerable strength and stiffness increases over a bare steel alternative. the depth of the beams themselves is reduced without incurring the expense and complexity of rigid. full strength connections . Construction Management | 5 . Floor grids comprise two layers of fully continuous beams running in orthogonal directions.2. A further benefit is that.1. Services running in either direction can be integrated within these two layers. By far the most common types of beam used today are plate girders.1. so that services passing in any direction can be accommodated within the structural floor depth. 2. Many of them exploit the benefits of composite construction . with some overlap between options.2 Parallel beam approach The parallel beam approach is effective for spans up to around 14 m. and beams with web openings (be they cellular .2 Long span beam options The solutions described below are presented in order of increasing spanning ability. being fully continuous. or rolled sections). fabricated.

and web post buckling may govern design (the web post is the section of web found between two adjacent openings.) Web openings are typically formed in beams to allow services to pass through the beam. This enables the structural and service zones to occupy the same space. Openings may also be formed for aesthetic reasons. The most appropriate solution to adopt depends on the size. The alternative way of forming the web openings is simply to cut them into the plate used to form the web of a plate girder. The design of beams with web openings must recognize the fact that the openings introduce a number of potential failure modes not found in solid web beams.1.1. or the web of a rolled section.3 Composite beams with web openings Figure 2. Beams with web openings present no disadvantages in terms of erection and familiarity as they are much the same as a 'standard' solid web beam. or more commercial drivers such as the method used by a preferred supplier.3a Service integration with cellular beams (Image courtesy of FABSEC Ltd. shape and regularity of the openings.2. as shown in the figure below). thereby reducing the effective overall depth of floor construction for a given spanning capability. Composite beams with web openings have been shown to be a cost effective solution for spans in the range 10 to 16 m. which is formed in a specific way and therefore described separately below . Large openings may require stiffening to avoid instability (buckling) of the web posts. Construction Management | 6 . for instance with cambered beams used to support a roof. A particular type of composite beam with web openings is the so-called cellular beam. Around the openings the beam behaves as a Vierendeel girder.

but not necessarily. The two Tees.3d: Cellular composite beams 2.1. based on extensive test programmes that have included fire testing. to form two Tee sections. The process used to form cellular beams enables the bottom half of the final beam to be formed from a heavier donor section than the top half .1 Cellular beams and services Cellular beams are a form of beam with multiple regular web openings .3c Composite beam with spaced openings stiffened web openings (Image courtesy of FABSEC Ltd. Figure 2.1.3. circular).Figure 2.1. formed by splitting two rolled sections longitudinally.in other words the bottom flange can be significantly bigger than the top flange.) The figure above right shows a composite plate girder with stiffened web openings. as is Construction Management | 7 . which may not come from the same donor section (as discussed below) are then welded together to form an I-section with web openings which have a characteristic shape (normally.1. This makes sense when.3b Modes of failure at large closely Figure 2. Dedicated design guidance (SCI P355) and software from specialist manufacturers is available.

Double (oval) openings may also be included to facilitate the passage of larger service ducts.) Tapered girders can be a cost effective solution in the span range 10 m to 20 m. with regular circular web openings.1. 2. and/or stiffening added to accommodate local features such as incoming beams or heavy point loads. It is also possible to form web openings in tapered girders in regions of low shear. towards mid- span. The figure below shows a cellular beam. and services sharing a common floor zone.4 Tapered girders Figure 2. Dedicated design guidance (SCI P355 ) and software is available from specialist manufacturers. Although cellular beams have regular openings some of these may be in filled.1. based on extensive test programmes that have included fire testing.4a : Tapered cellular girder (Image courtesy of FABSEC Ltd. These provide more options for service integration . the beams are to act compositely and therefore a concrete flange effectively replaces the upper steel flange in the final state (the upper steel flange only needs to be big enough to meet construction needs and serve as a platform for the shear studs). which must be observed to prevent excessive slip between the steel and concrete elements. The depth of the girder increases towards mid-span. where applied moments are greatest. The greater the asymmetry the more onerous the requirements for minimum degree of shear connection . Construction Management | 8 . and thereby facilitating hanging services under the shallower regions near the beam supports. They are another solution that allows services to be accommodated within the structural floor zone. BS EN 1994 provides design rules to cover beams with an asymmetry (area of the bottom steel flange divided by that of the upper flange) of up to three.often the case.

until composite action with the hardened concrete is achieved the beams may need temporary support/restraint. on which sit short lengths (stubs) of deeper I-sections (UKB). The number of Construction Management | 9 .4b : Tapered girder supporting steel decking 2. is formed by the composite slab. Detailed design guidance is available in SCI P059 . The top chord. Although this is based on design to BS 5950 the principles are readily transferrable to a Eurocode based approach. a rather exotic hybrid that can be thought of as lying somewhere between a solid web I-section and a truss.5 Stub girders Figure 2.1.1. Composite interaction is achieved by welding shear studs to the top of the UKB stubs. An inverted Tee section may be used to fulfil the functions of a top chord during erection.5a : Composite stub girders Stub girders are a Vierendeel form of truss.1. and therein lies one of the disadvantages of this option . The bottom chord is typically formed from a shallow open section (UKC). Figure 2. at least in the final state.

or FirmKolisch. Detailed design guidance is available in SCI P060.1. A ridge roof beam for a modular housing unit.6 Haunched composite beams Haunches may be added at the ends of a composite beam to provide moment continuity. hanging the services under the beams rather than passing them through holes in the webs. 2. or through a truss. which is in turn supporting a composite slab. 2. Construction Management | 10 . The beam includes an elongated plywood web and a pair of elongated wood flanges extending adjacent and parallel to opposite edge margins of the web and secured in face-to-face relation to one face of the web. the principles are readily transferrable to a Eurocode based approach.7 Ridge roof beam Primary Examiner-John E. Murtagh Attorney. and services passed under it. The web and flanges are each constructed of elongated wood sections bonded together in end-to-end relation. can be advantageous.elements/surfaces associated with a stub girder may increase the cost of fire protection compared with simpler solutions. Services and/or secondary beams can pass through the gaps between the beam stubs. Although this is based on design to BS 5950. Finger grooves extending along adjacent end edges of the sections interlock to form a secure joint there between. reducing overall construction depth. The figure on the right shows a composite stub girder supporting a secondary beam. The stiffness and strength of the connections mean that the rest of the span can be shallower (the bending moment diagram is 'lifted' and the effective stiffness of the beam substantially increased). A big advantage of this option is that spans in excess of 20 m can be economically achieved. Hartwell & Dickinson. Spans in excess of 20 m can readily be achieved. Agent. In buildings where the services are likely to need frequent replacement (for example in hospitals ).1.

Construction Management | 11 .1. gable end strut or held by means of angle strutting from internal walls. This is done using blocking pieces of the same timber as the ceiling joists. The ceiling joists are fixed to the hanging beam with:  hoop iron straps  timber battens or  purpose made metal joist hanger brackets. The function of a hanging beam is to reduce the span of the ceiling joists. They can be nailed or bolted to an available rafter.8 Hanging beams A 'hanging beam' is generally a deep timber beam located perpendicular (at right angles or 90º) to ceiling joists and directly above them. Hanging beams are held in a vertical position at both ends.2. Hanging beams must only support ceiling joists and the attached ceiling materials. The hanging beam has to be adequately supported on its ends over load bearing walls. This allows for a more economic joist size and consistent section.

2. Single roofs can be categorised as follows: Couple roof – These can be used for building with a clear span of not greater than 3m and pitches less than 40º.9 Roof System They have many types of roof systems. larger roof sections would be needed.1. Collar roof – These can be used for buildings with a clear span not exceeding 4mm.1. then this type of roof will have a tendency. If the feet of the rafters are not tied together by means of a binder or roof joist. Rafters of single roofs do not require any intermediate support.a  Single roofs. If greater spans are required. This type of roof has a number of limitations. underweight. Construction Management | 12 . Traditional roofs can be divided into three main types of structure: Figure 2. Close couple roof – These can be used for buildings with a clear span not exceeding 5.5mm and with pitches less than 25º. to push the supporting walls outwards at the top causing structural failure of the walls. It can only be used for small spans.9.

When subjected to any type of load or force acting vertically downwards the rafters will move outwards at their feet thus exerting thrust to the walls forcing them outwards and causing possible failure of the wall structure. When measuring rafters. This support is usually a beam which is secured under the rafters at a point half way between the ridge and the wall plate. a binder is fixed to each ceiling joist and hanger. the angle of the roof would be 45°. The roof consists of common rafters fixed at the ridge and at the wall plate. 2.  Roof pitch – This is the angle or slope of the roof and can be expressed in degrees or as a fraction or ratio found by dividing the rise by the span. This type of roof structure is very limited in its use.1 Pitches. A double roof is a roof whose rafters are of such a length that they require an intermediate support. This binder runs parallel with the main wall and at right angles to the ceiling joist. Construction Management | 13 . Spans and Rises When setting out a roof. the length is taken as a straight line running through the centre of the rafter. This type of structure ensures that this type of roof can be used for great spans without the fear of the roof spreading under loads.  Trussed roofs. To further increase the strength of this structure. Since the rise is half the span. there are certain essential factors that must be considered. This type use new technology to build the roof.  Roof height or rise – This is the vertical height of the roof at its highest point and is measured from the top of the wall plates to the intersection of the rafters at the top of the roof.10. This type of roof structure is very famous use in construction. These are:  Roof span – This is the distance across the roof and measured to the outer edges of the wall plates.  Double roofs.

12.a Raffer 2. and project 25mm from the face of the outer brickwork.1 Flush eaves In this method of finishing off the lowest edge of the roof. When determining the length of the rafter. Figure 2.2. an allowance is made for the thickness of the ridge and the length of the overhang at the eaves.11. Below are two examples:  Flush eaves. The rafter is seated upon the wall plate by means of a notch or birdsmouth joint which is cut one third into the rafter. Once the section has been set out the length of the common rafter can be determined by drawing the rise and the span as a right angle joined together by the hypotenuse which will determine the slope of the roof. The top angle or bevel is called the plumb cut.11. the rafter feet are cut plumb. The angle at which the notch is cut is called the seat cut.1 Rafter Length and Bevels The roof section can be set out full size or to scale. EAVES AND FASCIAS There are various ways of constructing the eaves of a gable roof. This will allow a ventilation gap to be formed so that a continuous flow of air can circulate throughout the roof Construction Management | 14 .  Roof Ventilation 2.12.  Boxed or closed eaves.

in some cases.space. The roof space can be ventilated by using a proprietary vermin proof ventilation strip or the soffit can be drilled with a series of holes into which plastic ventilators are fixed.12. The rafter feet are allowed to overhang the face of the outer brickwork. or is at a distance that can accommodate a proprietary ventilation soffit.  Using circular plastic ventilators set into the soffit board.  Using a proprietary ventilation strip.2 Closed or boxed eaves. 2. a piece of plywood cut to shape. or 25mm where the pitch of the roof is less than 15°. This is a more complex method of finishing the lowest edge of the roof. Construction Management | 15 .3Roof ventilation Roof ventilation is essential to reduce the likelihood of condensation within the roof space as required by the Building Regs 1985. The fascia board is nailed directly to the rafter feet to form a face trim. 2.12. There are many types and designs of proprietary ventilators available all of which have been designed to give sufficient ventilation to the roof space if used and incorporated into the structure correctly. The overhang can vary in size but usually the distance is stipulated on the working drawings. The soffit is supported by a cradling bracket or. The regulations state that all roofs must be cross-ventilated at eaves level by permanent vents and these must have an equivalent area equal to a continuous gap along both sides of the roof of 10mm. This ventilation requirement can be achieved by:  Leaving a gap between the outer wall and the soffit. It is to this fascia board that the guttering is fixed.

Construction Management | 16 . So the pitch is partly dependent upon stylistic factors. a single flat sheet or a complex arrangement of slopes. The main factors which influence the shape of roofs are the climate and the materials available for roof structure and the outer covering. the available roofing materials and the local traditions of construction and wider concepts of architectural design and practice and may also be governed by local or national legislation. and partially to do with practicalities. both the covering on the uppermost part of a building or shelter which provides protection from animals and weather. roofs are pitched for reasons of tradition and aesthetics. The characteristics of a roof are dependent upon the purpose of the building that it covers. The durability of a roof is a matter of concern because the roof is often the least accessible part of a building for purposes of repair and renewal. Roof shapes vary from almost flat to steeply pitch. In most countries a roof protects primarily against rain. A veranda may be roofed with material that protects against sunlight but admits the other elements. The roof of a garden conservatory. for example a roof garden. protects plants from cold. or from one builder or architect to another. Most US domestic architecture. or truncated (terraced. notably rain.0 SUMMARY A roof of a building envelope. 5. while its damage or destruction can have serious effects. but also heat.0 CONCLUSION Roof shapes differ greatly from region to region. They can be arched or domed. wind and rain but admits light. has roofs that are sloped. or pitched. except in very dry regions. wind and sunlight.4. Although modern construction elements such as drainpipes may remove the need for pitch. Roof terminology is also not rigidly defined and usages vary slightly from region to region. gables and hips. The pitch is the angle at which the roof rises from its lowest to highest point. The construction of a roof is determined by its method of support and how the underneath space is bridged and whether or not the roof is pitched. A roof may also provide additional living space. cut) to minimize the overall height. and the framing or structure which supports the covering.

Van Huylenbroeck. Sept/Oct 2008.2013. Gellynck.landurbplan.05.005.07. Retrieved 10 June 2008. doi: 10. B.1016/j. Sustainable Cities and Society 10: 59–64. 17 November 2005. 2011). Valerie. 52–53  University of Toronto – News@UofT – Green roofs in winter: Hot design for a cold climate". X..2011. Dvorak (February 2014). Archived from the original on 11 April 2008. "The use of economic valuation to create public support for green infrastructure investments in urban areas". Retrieved 27 February 2014. substrate water content and vegetation affect storm water retention efficiency of an un-irrigated extensive green roof system in Central Texas". Construction Management | 17 . Astrid.6. (November 30.scs. cover and pp.010. Verspecht.  Volder. Retrieved 28 February 2014. JEAN research website. A.  Vegetated Complex Partition research presentation on Aurélien P.1016/j.. G.0 REFERENCES  Vandermeulen. Vermeire. "Event size. Landscape and Urban Planning 103 (2): 198–206.  California (magazine of the University of California Alumni Association). doi: 10..

7.0 APPENDIX Construction Management | 18 .