Pure Asphalt Pacoflex Polymer Modified Mastic Asphalt Technical Design Guide
PURE ASPHALT - PACOFLEX POLYMER MODIFIED MASTIC ASPHALT Pacoflex Polymer modified mastic Asphalt is manufactured by Pure Asphalt in the United Kingdom and distributed and installed by Asphaltech in New Zealand. Pure Asphalt have manufactured mastic asphalt products since the 1930s. All products are manufactured to British Standards and have been independently tested and have BBA Certification. Asphaltech are a leading provider of Mastic Asphalt systems here in New Zealand, offering a single source approach to supply and installation of mastic asphalt. This enables our company to provide the appropriate technical advice, specification and project management service from the first point of contact through to completion of your project. OUR QUALITY Quality product- Pacoflex is produced by Pure Asphalt to British standards and is manufactured to ISO 9000 Quality management system. It carries a BBA certificate. Pure Asphalt is a member of the Mastic Asphalt council of Britain and Europe. Quality design- Our Single point of contact throughout the project improves design, speeds up decisions and ensures continuity and reliability. Our technical design team comprises of a trained architect and a fully Qualified Mastic Asphalt Technician. Quality Workmanship- For many years Asphaltech has been installing Mastic Asphalt to some of New Zealand s most innovative buildings. Our team are extensively trained and have completed City and guilds training in Mastic Asphalt roofing. 1.
Mastic Asphalt INTRODUCTION Mastic Asphalt is an ideal material for a whole range of construction applications, in both new build and refurbishment, where a smooth, seamless, durable suface is required. Polymer bitumens are designed to improve durability, iit s temperature susceptibility and it s resistance to cracking and stripping when used in finished products such as mastic asphalt. It offers total waterproofing integrity for roofing and tanking and acts as a tough working surface in flooring and paving. Mastic Asphalt is one of the world s most traditional construction materials and has continued to develop with the times, even in today s hi-tech building industry. The product comprises of suitably graded limestone aggregates bound together with asphalt cement (primarily refined bitumens) to produce a dense, void-less material. It cannot be compacted, and is spread by means of a hand float (rather than rolled). Today s modern mastic asphalt contains highly advanced polymer formulations. A VERY VERSATILE CONSTRUCTION MATERIAL As a roofing material mastic asphalt is ideal for use as a waterproof covering over flat, sloped or curved surfaces. It can be worked round pipes, roof lights and other projections. It can be laid on most types of rigid sub-structures such as concrete, pre-cast concrete deck units, timber boarding, metal decking and other proprietary decking units. Thermal insulation materials can easily be laid as part of mastic asphalt specification to achieve the required U-value. Treatments applied to asphalt can provide a surface suitable for traffic, increase solar reflectivity and provide a decorative finish. THE NEW POLYMER MODIFIED MASTIC ASPHALTS Polymer modified binders are used by Pure Asphalt in the manufacture of waterproofing, paving and flooring grades of mastic asphalt. Mastic Asphalt, Auckland War Memorial Museum Benefits of Mastic Asphalt DURABILITY Mastic asphalt is the premier bituminous waterproofing and surfacing product available. Mastic asphalt has the ability to last up to 40 years. The polymers used in mastic asphalt improve elasticity in both hot and cold weather conditions, which help to maintain its structural integrity and durability. WATERPROOF Mastic asphalt is unaffected by water and provides a proven seamless waterproofing and tanking material that is second to none. COST-EFFECTIVE Because it outlasts all other bituminous materials mastic asphalt doesn t need replacing as often, thus delaying expensive replacement costs wfor many years. MAINTAINS IT S APPEARANCE Mastic asphalt can also be made fuel and acid resistant and can be cleaned with pressure water jets without damaging the surface, unlike other bituminous surfacing materials, which can suffer water damage. Asphaltech Limited Ltd. Technical Design Technical Guide Design 09 Guide 475 9725 www.asphaltech.co.nz 2.
Benefits of Mastic Asphalt (cont.) ENVIRONMENTALLY FRIENDLY Mastic asphalt is a potentially 100% recyclable product and is classified as non-toxic. DESIGN FLEXIBILITY Mastic asphalt in its molten state can be moulded to any irregular shape and be laid around any obstruction in-situ FASTER PROJECT COMPLETION Mastic asphalt can be laid quickly over large areas. Contracts can be supplied in block form for re-melting the required quantity on-site, with a rapid cooling time the Mastic Asphalt becomes a waterproof surface almost immediately. DOMESTIC AND COMMERCIAL FLOORING As well as a proven damp-proof membrane, mastic asphalt applied to domestic floors provides the ideal base for carpet, vinyl or other types of smooth flooring. Its speed of application and fast cooling properties allow carpets and furnishings to be replaced within hours. Many European countries are renovating their old blocks of flats and are installing sound proofing to their floors overlaid with a new mastic asphalt flooring layer. There are no moisture considerations, curing or drying out times with mastic asphalt floors. DESIGNING WITH COLOUR To the architect or project manager mastic asphalt offers limitless scope for design opportunities. It can be specified in almost any colour, texture and design and is an ideal choice where general aesthetics have to be combined with long-lasting waterproofing or paving. HEALTH & SAFETY Unlike brick and block paving, mastic asphalt is laid in a continuous film without the need for joints, which means that accidents such as slips, trips and falls are reduced. Mastic asphalt provides a safe non-slip surface for pedestrians and non-skid carriageway for vehicles. Award winning ANZ Tower Project. 3.
Design Considerations GENERAL The structural deck provides the primary support for the roofing system. It must resist dead, live and wind loads, including storms. It must also be suitable for the proposed Polymer Modified Mastic Asphalt roofing system, and subsequent use. Relevant structural and loading codes for each material must be followed, and the requirements of the current Building Regulations must be checked and observed. If the use of the roof is to be changed, the suitability of the deck and the structure must be re-confirmed. The deck must also be laid or fixed so as to provide a suitable fall for drainage of the roof surface, as required in BS 6229, Code of Practice for flat roofs with continuously supported coverings. THE MOST COMMON TYPES OF FLAT ROOF STRUCTURAL DECK ARE: (All works must be in accordance with the manufacturer s specifications and any engineer s directives). IN-SITU CONCRETE DECKS Cast in-situ reinforced concrete decks can be laid to achieve an adequate fall, or a screed can be laid to falls. The finished surface must be adequately dry to accept the specified Polymer Modified Mastic Asphalt roof waterproofing system, and free of any ridges or hollows. The most suitable surface is provided by a wood float finish. Construction water should be drained by forming temporary drainage holes through the slab, as specified in NZBC E2/ASI Acceptable solution.. treatment. Lay with staggered joints (brick bond) with all edges of the sheets fully supported or with tongue and groove jointing. Provide 20mm H3.2 timber fillets at the base of all upstands and chamfer all external edges with a minimum radius of 5mm. Fix with 10 gauge x 50mm stainless steel countersunk head screws, with a 3mm gap between all sheets. Fix at 150mm centres on edges and 200mm in the body of the sheets. Plywood and the timber substructure to have a maximum moisture content of 20% when the membrane is adhered. Consult with plywoodmanufacturer s correct testing technique. Provide whichever is the greater falls: - as shown on the drawings - to the membrane manufacturer s requirements - minimum to NZBC E2/AS1, 8.5.1, - 1:30 for roofs, 1:40 for decks and 1:100 for gutters... PRE-CAST CONCRETE DECKS A variety of pre-cast deck units are available, and these should be used and fixed in accordance with manufacturer s instructions. A screed is normally required to provide an even surface for waterproofing and to provide drainage falls, if falls cannot be incorporated in the supporting structure. Construction water should be minimised, and where present, drained by leaving the deck joints open on the underside. PLYWOOD DECKS / SUBSTRATE Plywood to be a minimum of 17mm thick and complying with AS/NZS 2269.0, minimum CD structural grade with the sanded C side upwards. Hazard Class H3.2 with waterborne CCA treatment and kiln dried after CHANCERY DOMES; Mastic Asphalt to timber substrate. 4.
Falls and Drainage DESIGN OF FALLS It is generally accepted as good practice for flat roofs to be designed to clear surface water and it would be unusual for a Polymer Modified Mastic Asphalt roof to be designed without falls, other than within a three coat protected membrane Polymer Modified Mastic Asphalt full bond specification. Flat roofs should be constructed to a minimum fall of 1 in 80. To achieve this, the designer needs to adopt a design fall which will allow for deflections and inaccuracies in construction. BS 6229 recommends 1 in 40 as the design fall, to ensure a finished fall of at least 1 in 80. An alternative approach is to choose an intermediate figure of 1 in 60, which is usually sufficient. The design of falls and drainage patterns will have a considerable influence on the depth of the total roof construction or roof zone, which should be a fundamental consideration at the very earliest stages of conception of a building. It is only after assessing the depth of roof zone that the designer can decide the levels of all other aspects of construction above the level of the flat roof. ROOF DRAINAGE Flat roofs may be drained by two basic methods: towards the outer edges and into external gutters, or towards internal gutters or outlets within the main roof area. Straight falls to external gutters are simple to form by screeding or using tapered timber strips. Internal drainage will be achieved by straight falls to gutters or a pattern of falls and cross falls to outlets. Wellington fire station Keying to Surfaces CONCRETE Mastic Asphalt Horizontal Falls may be formed in the structure or can be created within the specification above the deck. Falls in the structure can be achieved by adjusting the height of supporting beams or purlins, by using tapered supports, or by the addition of firring pieces before the deck is laid. The latter method is normally used with decks such as timber, precast concrete and metal decking. In the case of an in-situ cast concrete slab, falls are normally provided by using a screed. In some circumstances it may be deemed necessary to control the rate of water run-off from flat roofs and paved areas so as to avoid overloading ground drainage. Where this is a requirement, consideration should be given to using green roofs or roof top gardens where the horticultural finishes can be used to absorb rainfall and release it into surface water more slowly. However, it is still important to make the correct provision for adequate drainage, even with garden roofs, to avoid water-logging the growing medium or overloading the structure. Where vertical or sloping concrete is very smooth (e.g. where steel shuttering has been used), the surface laitance should be removed by wire brush or suitable mechanical means to provide a satisfactory key for the Polymer Modified Mastic Asphalt. Note: Damage to Polymer Modified Mastic Asphalt and loss of key will be caused by excessive use of mould oil. Apply a light brush coat of High Bond Primer and allow it to dry thoroughly before applying Polymer Modified Mastic Asphalt. Where excessive blowing is experienced the fixing of bitumen coated expanded metal lathing over black sheathing felt may be required. BRICKWORK Joints in brickwork should be flush pointed. The surface must be cleaned and High Bond primer applied to avoid blistering or loss of bond. TIMBER The key to vertical or sloping timber surfaces is obtained by fixing galvanised expanded metal lathing over black sheathing felt fixed with extra-large head galvanised felt nails or with galvanised staples at maximum 150mm centres. 5.
Control of Condensation GENERAL PROVISIONS When designing a roof the problem of condensation must always be borne in mind. Any provision required to control condensation should be determined as recommended in BS 6229 but with the calculation method modified to conform to BS 5250: 2002, Code of Practice for control of condensation in buildings. In the case of a roof incorporating Polymer Modified Mastic Asphalt, a suitable thermal insulation maybe included within the system. This layer must have sufficient insulation value for its underside to remain above the temperature at which condensation can start, even on the coldest nights. The provision of insulation alone, however, may not be sufficient to prevent condensation. If the insulation is permeable to water vapour, the vapour will pass upwards through it and condense on the underside of the waterproof membrane. To prevent this, a vapour control layer in the form of a vapour barrier should be provided on the underside of the insulation. A vapour barrier can be an approved metal lined vapour barrier or 13mm thick single coat of Polymer Modified Mastic Asphalt roofing on an underlay of glass fibre tissue. N.B. The need for a separate vapour control layer may be avoided by specifying the inverted roof system or a full bond system. INSULATION There are 2 common types of insulated roofing systems the Inverted roof or cold roof or the Warm roof system INVERTED ROOF SYSTEM Kingspan Styrozone is a high performance ridged extruded polystyrene board that is laid directly on the mastic asphalt system providing protection to the waterproofing due to its high compressive strength as well as insulating the building. It is compatible with green roof systems for today s conscientious designers. Guidance on thermal performance must be sought from manufacturer. WARM ROOF SYSTEM Kingspan T27 is a high performance CFC/HCFC free polyisocyenerate (PIR) base formulation board. In this application the boards are laid below the mastic asphalt system, bonded directly onto a vapour control layer. The boards should be laid in a brick bond pattern with edges pushed firmly together. Guidance on thermal performance must be sought from the manufacturer. SCREEDS Screeds provide a suitable surface to receive Polymer Modified Mastic Asphalt and can also be used to achieve falls and cross-falls. In addition, some screeds can provide a level of thermal insulation and contribute to the U-value of the roof. SAND AND CEMENT SCREEDS Sand and cement screeds are normally mixed in the ratio 4:1 and the surface should be finished with a wood float. The screed should be laid directly onto the deck to obtain a good key. It should be laid in areas not exceeding 10m², to reduce the incidence of cracking due to drying and shrinkage. These screeds contain considerable amounts of water and the surface should be adequately cured and dry before the Polymer Modified Mastic Asphalt roofing specification is applied. Where screeds are formed or supported on permanent shuttering or metal profiles, provision must be made for water to drain adequately, in accordance with the manufacturer s instructions. AERATED SCREEDS Aerated screeds consist of Portland cement, water and a foaming emulsion, which are combined to produce a cellular material; this offers a hard surface when dry. LIGHTWEIGHT AGGREGATE SCREEDS (CEMENT BONDED) Suitable lightweight aggregates are formed from expanded clay or sintered pulverised fuel ash, bonded with a cement binder. The material must be laid soon after mixing; otherwise the cement binder could dry too fast, and not bond the aggregate together. A 13mm sand and cement topping is necessary to provide a smooth level surface for the roofing specification. INSULATING CEMENT SCREEDS A range of cement based screeds containing Perlite, Vermiculite, recycled EPS and other additives are available from various sources. These are often of a lighter weight than just sand and cement and impart a degree of insulation to the roof structure. Guidance on the thermal performance and installation of these products must be sought from the individual manufacturer concerned 6.
Application of Polymer Modified Mastic Asphalt The application of Polymer Modified Mastic Asphalt should be in accordance with BS 8218 and BS 8000: Part 4. FLAT ROOFS UP TO 10 Polymer Modified Mastic Asphalt is normally laid in two coats, with staggered joints, to nominal thickness of 2 x 10mm = 20mm on an underlay of black sheathing felt laid loose with 50mm lapped joints. Where thermal insulation is laid beneath the weatherproofing, it is recommended that the roof pitch does not exceed 5. SLOPES OVER 10 AND VERTICAL SURFACES (EXCLUDING SKIRTINGS) Polymer Modified Mastic Asphalt laid on concrete or screeded substructures of 10 to 30 slope is applied in two coats to a nominal thickness of 20mm direct to the concrete. For vertical work over 300mm and slopes over 30 Polymer Modified Mastic Asphalt is applied in three coats, the first coat being applied very thinly with a steel trowel or small wooden float. A further two coats are then applied, breaking joint, to give a nominal thickness of 20mm. For these applications the concrete must be left with a roughened surface to form a key for the Polymer Modified Mastic Asphalt. In the case of sloping timber surfaces over 10, a layer of black sheathing felt is first nailed to the timber. Galvanised expanded metal lathing is then fixed at 150mm centres with galvanised clout nails or staples to form a key for the Polymer Modified Mastic Asphalt which is applied in three coats to a nominal thickness of 20mm. SAND RUBBING With the exception of vertical and steeply sloping work, clean sharp sand should be rubbed evenly into the finished surface of the asphalt with a wooden float while it is still hot. This rubbing breaks up the skin of bitumen brought to the surface at the time of application. Gradual crazing of the surface due to the action of the sun is minimised by sand rubbing in this way SKIRTINGS AND FLASHINGS In the case of concrete, brickwork and similar sub-structures, a two-coat Polymer Modified Mastic Asphalt skirting is necessary at all up stands to a nominal thickness of 13mm and a minimum height of 150mm above finished roof level. A two-coat angle fillet should be formed at the junction of the vertical and the flat. The top of the skirting is splayed and turned into a chase 25mm x 25mm unless the asphalt continues horizontally. Skirting s above 300mm high are regarded as shown vertical and Polymer Modified Mastic Asphalt is applied in three coats to a nominal thickness of 20mm. Where differential movement is likely to occur between the roof deck and up stands e.g. substrates consisting of timber board, or metal, a free standing up stand fixed to the deck minimum 12mm clear of walls and abutments is necessary. This is usually provided by a timber kerb or metal angle with plywood facing. Polymer Modified Mastic Asphalt is then applied in three coats to a total thickness of 20mm on to expanded metal lathing fixed over black sheathing felt. The skirting is cover-flashed and protected by an application of solar reflective paint. Where insulation is used beneath Polymer Modified Mastic Asphalt, but not continued up the verticals, a minimum 25mm wide support leg to the skirting is essential. Alternatively a flexible up stand incorporating Polymer Modified Mastic Asphalt high performance bitumen membranes can be used. RAINWATER OUTLETS A number of outlets can be used in conjunction with Polymer Modified Mastic Asphalt but cast bronze or spun aluminium outlets with a bell mouth and internal clamp ring are particularly recommended ANZ Tower, podium refurbishment, planter. Where a syphonic drainage system is required, the outlets must be designed specifically for use with mastic asphalt. For further details please contact Technical Services. 7.
GUTTERS Where the roof fall is into an eaves gutter the asphalt can be finished over a lead flashing set into a rebate in the sub-structure. The lead must be welded at the back and the depth of the rebate must allow for a full thickness of Polymer Modified Mastic Asphalt over the welt. Alternatively, an apron or purposely made GRP Edge Trim can be used. suitability of PVC and metal roof light kerbs to receive Polymer Modified Mastic Asphalt directly must be obtained from the manufacturer. However, a timber facing fixed to the kerb followed by expanded metal lathing fixed over black sheathing felt would normally be required. Gutters can be lined in Polymer Modified Mastic Asphalt to follow any shape of contour in the substructure. Where a gutter is formed between a parapet wall and a tiled or pitched roof, the Polymer Modified Mastic Asphalt is carried up the slope and over the tilting fillet. It is generally preferable to avoid the use of integral gutters on flat roofs, using, instead, falls and cross falls to direct the flow of water to rainwater outlets. MOVEMENT JOINTS Twin kerb movement joints are recommended with a metal cap flashing fixed to one kerb only, or a capping system held by cleats or spring clips. In either case suitable fixings should be provided to avoid penetrating the asphalt. All ends should be boxed as necessary to complete the waterproofing but still allow movement. The design of the structure should avoid flush surface movement joints if at all possible. However, proprietary systems are available for this application and specialist advice is necessary. Vapour Control Layer PLINTHS pipe protruding thru insulated roof detail. Plinths to receive rooftop equipment must be constructed off the deck or screed level. Polymer Modified Mastic Asphalt is dressed in a minimum 150mm above finished roof level and the top protected with a cover flashing. Note. These are the British Standard guidelines. All works undertaken in New Zealand must comply with the relevant New Zealand standards and the NZ building codes. All structures must also be checked or designed by an Engineer. PROJECTIONS THROUGH ROOFS Projections passing through the roof, such as handrails, stanchions and metal pipes, can usually receive a collar direct. Polymer Modified Mastic Asphalt is then dressed 150mm above finished roof level and the upper edge protected with an apron flashing. In situations where Polymer Modified Mastic Asphalt cannot be applied directly to the projection, a lead sleeve should be fixed to the substrate. ROOF LIGHTS AND VENTILATORS Roof lights and ventilators should be mounted on kerbs minimum 150mm above the roof finish. Polymer Modified Mastic Asphalt is then taken up the side and over the top of the kerb. Proprietary kerb adaptors are recommended for such details and these must be applied before the roof light is fixed. Advice on the Inverted Green Roof, Stamford Plaza. 8.
Applications for Polymer Modified Mastic Asphalt SUITABLE SUBSTRATES TO SUPPORT MASTIC ASPHALT : CONCRETE, TIMBER & METAL TRAY DECKING FLAT ROOFS Where Polymer Modified Mastic Asphalt is required as a roofing surface only with little or no traffic, it is laid in two coats to a nominal thickness of 20mm. The first coat is laid to a thickness of 10mm and the second coat 10mm. It is applied in a liquid form and spread out to form and homogenous surface which whilst liquid can be formed to any shape or surface as required. It can then be protected by a solar reflective UV resistant paint. CAR PARK TRAFFICABLE SURFACES These trafficable roofs are recognised as one of the most durable car parking waterproofing systems available and are used extensively throughout the country. They consist of two layers of the Polymer Modified Mastic Asphalt with a wear slab of either reinforced concrete or a layer of Hot Mix Roading grade asphalt. These toppings vary in thickness subject to their final requirements. Separation Layer Paving layer nominal thickness Separation Layer 20mm Two Coat Mastic Asphalt Concrete Deck Mastic Asphalt roofing nominal thickness Concrete Deck Asphaltech mastic asphalt to concrete roof / deck Asphaltech car park surface construction Asphaltech mastic asphalt to concrete upstand X-sectional detail Asphaltech car park / roof parapet outletdrain detail 9.
SUITABLE SUBSTRATES TO SUPPORT MASTIC ASPHALT : CONCRETE, TIMBER & METAL TRAY DECKING TERRACES AND BALCONIES Where Polymer Modified Mastic Asphalt is required as an exposed paving subjected to foot traffic only, it is laid in two coats to a nominal thickness of 25mm. The first coat is laid to a thickness of 10mm and the second coat 15mm incorporating 15% by weight of coarse aggregate. Where insulation is incorporated beneath Polymer Modified Mastic Asphalt on balconies and terraces, or in situations where point loading is anticipated, promenade surfacing should be provided by suitable concrete tiles or paving slabs. GREEN ROOFS Polymer Modified Mastic Asphalt is an ideal waterproofing material for extensive green roofs, intensive roof gardens and biodiversity roofs. These finished can enhance environments, control water run off, and reduce noise transmission. Extensive green roofs require little long term maintenance. It is completely resistant to root penetration and d oes not require an additional anti-root barrier. Paver Support Selected Paver or Tile Separation Layer Planting Drainage Cell & Geotextile Sheet Separation Layer 20mm Two Coat Mastic Asphalt Concrete Deck 20mm Two Coat Mastic Asphalt Concrete Deck Asphaltech podium roof / deck construction Asphaltech green roof construction Asphaltech podium / concrete upstand / edge trim X-sectional detail Asphaltech green roof / concrete upstand / cap-flashing X-sectional detail 10.
Applications for Polymer Modified Mastic Asphalt SUITABLE SUBSTRATES TO SUPPORT MASTIC ASPHALT : CONCRETE, TIMBER & METAL TRAY DECKING THERMAL INSULATION IN ROOF DECKS AND TERRACES (warm roof construction) Kingspan T27 is a high performance CFC/HCFC free polyisocyenerate (PIR) base formulation board. In this application the boards are laid below the mastic asphalt system, bonded directly onto a vapour control layer. The boards should be laid in a brick bond pattern with edges pushed firmly together. Guidance on thermal performance must be sought from the manufacturer. INVERTED ROOF CONSTRUCTION We use the next generation in extruded polystyrene. These are the preferred polystyrene for the environmentally aware. Unlike most XPS products which are blown with HFC s or HCFC s, the new polystyrenes are ODP chemical free; it is in fact blown with air. These products provide ideal substrates for Asphaltech in standard warm roof systems. U-VALUE GUIDANCE : Technical information and design can be arranged to suit your needs. Separation Layer Rigid insulation board Paver Support Protection Layer Selected Paver or Tile Rigid insulation board 20mm Two Coat Mastic Asphalt Concrete Deck 20mm Two Coat Mastic Asphalt Separation Layer Concrete Deck Asphaltech insulated roof construction Asphaltech inverted roof construction Vapour Control Layer Asphaltech insulated car park-roof X-sectional detail Asphaltech inverted-insulated roof X-sectional 11.
Mastic Asphalt Systems Details Concrete capped parapet detail. Cast concrete upstand detail. Change of level detail. Cladding upstand detail. Drip edge detail. Outlet detail. Parapet outlet detail. Threshold upstand detail. Torch on upstand detail. 12.
Mastic Asphalt Maintenance Pacofelx Polymer Modified Mastic Asphalt Maintenance and repair schedule 1). General A flat roof which has been designed and installed in accordance with the recommendations of our specifications and relevant British standards can be expected to provide trouble free service provided it is maintained. Maintenance inspections should be carried out regularly by persons knowledgeable in mastic asphalt work. Mastic asphalt roofs should be inspected annual, preferably in the autumn, to clear leaves, debris and dirt which may prevent proper drainage or cause deterioration, and to identify at an early stage are sights of failure. Where the roof is in an area of high dust or pollution, or in close proximity to trees, more frequent inspection may be necessary. Inspection should be carried out both externally and internally. Particular attention should be given externally to roof covering abutments, joints, gutters and outlets and internally to corners, abutments and penetrations. Observations by occupants of the buildings should be noted. 2). Maintenance check list for roofs (all in accordance with the code of practice BS 8218:1998) During the course of regular maintenance inspection the whole of the roof should be systematically checked and a note made of any items requiring attention. The following checklist should be used. a) Surfaces finishes and solar reflectors Check that surface chippings are evenly distributed and unaffected by wind scour and that ballast has not been displaced. Note any cracked or damaged tiles and slabs. Where reflection paint has been used, assess the necessity for renewal, taking into account the roofs age its formation, i.e. the presence and type of insulation etc. b) Skirtings, kerbs and turndowns Check the upstands are intact and fully adhered. Note any blistering, distortions or slumping. Pay particular attention to fillets and arise for cracks from movement or impact. Where skirting are tucked into a chase in concrete or brickwork, check the condition of the pointing. c) Edge trimmings Check for signs of movement displacement or stress, particularly at the joints between adjacent section for trim, and for retraction between asphalt and back edge of trim. d) Drainage Ensure that all gutters, rainwater outlets and discharge points are clean and that the water discharge from the roofs is uninterrupted. Carefully examine the junction between the asphalt and rainwater outlet. Note any apparent defects or signs of silting or ponding. e) General area Examine the whole of the general roof area, note any areas of stress or blistering and any signs of hollowing denoting failure of insulant or timber. Record the extent and type of any defects. 3). Repair procedures (all in accordance with the code of practice BS 8218:1998) Repairs should only be carried out after the type and extent of any defects have been noted and their underlying cause is identified. The intention of repair work should be restore the asphalt to its original condition and ensure its continuing performance. All repairs should therefore be carried out using materials, accessories and a standard of workmanship comparable with the original installation. Any surface treatment that has been damaged or displaced should be made good to match the existing surface. Defective pointing should be broken out and renewed. Split or broken non ferrous metal cover flashings should be repaired or renewed as necessary. Excessive blistering may be indicative of more serious underlying problems and should be cut out and the substrate examined to establish the cause. All repair work to a mastic asphalt surface should be performed by a qualified mastic asphalt operative. If it is necessary to remove an area of mastic asphalt, the line of the cuts should be covered with molten mastic asphalt until the underlying material has softened. The mastic asphalt should not be removed until this has taken place. In no circumstances should hammer and chisel be used to cut cold mastic asphalt. Alternatively, a disc cutter may be used to remove mastic asphalt. When the area is sufficiently soft, it should be removed carefully. When jointing new mastic asphalt to existing mastic asphalt, the principle of the lapped joint should be observed. The perimeter of existing mastic asphalt should be softened to permit removal of material to a depth of half its thickness for a width if not less than 75mm. Due to the hardness of mastic asphalt paving, electrical or mechanical disc cutters may be used in the removal of defective areas. The use of a forced flow hot air torch or the controlled use of a gas gun may be acceptable for specific requirements; in the case of the latter extreme care should be taken to avoid contact between the naked flame and the mastic asphalt. 13.
Mastic Asphalt Warranty 14.
Asphaltech Limited 30B Parkway Drive, Mairangi Bay, Auckland. www.asphaltech.co.nz P : 09 475 9725 F : 09 475 9726 info@asphaltech.co.nz