Terrace Home Guide An overview of intertenancy options CBI 5113
NATIONAL SUPPORT VISIT: Winstone Wallboards Limited 37 Felix Street, Penrose 1061, Auckland, New Zealand POST: PO Box 12 256, Penrose 1642, Auckland, New Zealand PHONE: +64 9 633 0100 FAX: +64 9 633 0101 Free Fax: 0800 229 222 EMAIL: info@gib.co.nz WEB: gib.co.nz GIB HELPLINE 0800 100 442 Our cities are becoming denser, urban populations are growing, land prices are rising, and this is impacting the types of homes we are building. BRANZ is forecasting that by 2017, multi-unit dwellings (apartments/townhouses/ units) will make up a third of all new consented dwellings, and in Auckland this will be close to 50 per cent*. Attached dwellings present design challenges that don t appear when designing detached houses. New Zealand Building Code (NZBC) provisions that typically do not apply to detached dwellings need to be considered in the design and construction of terrace homes. These provisions include protection from fire and airborne sound. *National Construction Pipeline Report 3, July 2015. front cover: Interior of a Warren and Mahoney terrace home in Christchurch. left: Terrace homes are growing in popularity, particularly in Auckland and Christchurch. 2 GIB TERRACE HOME GUIDE GIB TERRACE HOME GUIDE 3
CONTENTS Helping you find the right 5 system for your project Performance 6 NZBC requirements relating 6 to sound transmission Best practice sound 6 Environmental and services noise 6 Gaps, flanking and insulation 7 NZBC requirements relating 7 to protection from fire Penetrations through fire 8 and noise separations Plumbing and ducting 8 Electrical 8 Helping you find the right intertenancy system for your project This visual guide was developed to help navigate through the design and construction challenges of terrace homes and to provide a summary of some of the different intertenancy systems and solutions available, as well as clarify their performance requirements. Throughout, this document will direct you to specific support and systems literature for technical assistance and details. The GIB Helpline is always available where our technical team of builders and engineers can provide GIB specification assistance. Other design considerations 9 Security 10 Unit value and sale price 10 Raise the ceiling 10 Fussy details, site tolerances and 10 additional trades add complexity Intertenancy system weight 10 The right intertenancy system for the situation 10 GIB warranty 10 The cost of the intertenancy specification 11 Comparing intertenancy systems 12 GIB Systems 15 Double timber frame systems 15 GIB Intertenancy Barrierline Systems 17 Beware of substitution 18 Copyright 18 A precast concrete intertenancy wall erected on an Auckland terrace home site. 4 GIB TERRACE HOME GUIDE GIB TERRACE HOME GUIDE 5
Performance The physical arrangement of a terrace home can present challenges when trying to comply with the performance requirements of the New Zealand Building Code (NZBC). Meeting NZBC requirements is of the highest priority, but cost and ease of construction also impact on the choice of intertenancy system. From different levels of noise control or fire protection to considerations like accessibility, understanding the impacts of different characteristics is essential when choosing the most appropriate solution for your site and customers. NZBC Clause G6 Acceptable Solution G6/AS1 suggests the following construction techniques to minimise the level of sound transmission through building elements: Physical separation of each face of any wall which is common to two or more occupied spaces. Use noise control building elements. Avoid rigid service connections, such as plumbing services, where reticulation passes through an intertenancy wall. Make the installation airtight by sealing all joints and around penetrations and service fittings. NZBC Clause G6/AS1 comments that intertenancy GAPS, FLANKING AND INSULATION Noise can seep out of any gap, adding to reliance on good design and workmanship when constructing intertenancy walls. Although acoustic seals and sealants can be useful, best practice is to avoid gaps in intertenancy walls. Sound can also travel along structural elements like steel beams. If structural elements run through intertenancy walls, seek specialist acoustic engineering advice. Correct fibrous insulation is important to mitigate the transmission of sound. Closely follow GIB Noise Control System specifications. What makes good NZBC requirements relating to protection from fire Compared with detached houses, attached houses require fire walls between tenancies. Passive fire systems protect adjacent property and create safe environments for homeowners. However, they are frequently incorrectly designed and installed, or later compromised. NZBC Acceptable Solution C/AS1 requires common walls between terrace homes to have a minimum 30 minute Fire Resistance Rating (FRR). All the systems listed in this guide meet or exceed this requirement. NZBC requirements relating to sound transmission Research has found that owners and occupiers are increasingly unsatisfied with noise transmission levels at the minimum Building Code level and we strongly advise that these requirements are exceeded for most intertenancy situations. Aim for higher levels of noise control. NZBC Clause G6 Airborne and Impact Sound aims to protect people from the effects of undue noise transmitted between abutting occupancies. Terrace homes have at least one vertical intertenancy separation and the performance requirements of NZBC Clause G6 state that intertenancy walls shall have a laboratory tested Sound Transmission Class (STC) of no less than 55. Verification Method G6/VM1 states that field results shall be within 5dB of these performance requirements and common interpretation is that a Field STC (FSTC) 50 complies with the minimum NZBC requirements. walls should not be used for mounting fixtures and appliances which are likely to be a source of noise e.g. telephones, TV sets, stereos, cupboards with doors and service switches. Where the location of services in intertenancy walls is unavoidable, they may require additional treatment to ensure that noise control performance is not degraded. To limit transmission of impact noise on walls, soft close drawers and cupboard doors are simple and effective solutions for cabinetry. Locate driers and the like on external walls or other non-critical walls. When positioned on the floor, place them on resilient mountings. Impact Insulation Class (IIC) and Field IIC (FIIC) only apply to floor/ceiling elements that form an intertenancy separation. Full details for ceiling/floor systems are found in the GIB Noise Control Systems literature. Best practice sound ENVIRONMENTAL AND SERVICES NOISE Environmental noise from traffic, street noise or cafes, is currently not specifically covered by the NZBC, thermal insulation is not always an ideal acoustic absorber. Rigid insulation like polystyrene has great thermal properties but can reduce STC ratings rather than improving them. A puncture in a bag filled with water no matter how small will cause water to leak out. Noise is the same any gap will allow sound to pass through, degrading noise control performance. An FRR is determined by standard furnace testing and represents three outcomes in minutes: Structural adequacy the time a prototype specimen continues to carry its applied load. Integrity the time for which a prototype specimen prevents the passage of flames and hot gases. Insulation the time for which a prototype specimen limits the transmission of heat. Care must be taken to ensure accurate design and construction of elements required to have an FRR. Aspects such as junctions and penetrations are best accommodated with forethought and early communication between all parties involved in design and construction. but under the Resource Management Act (RMA) some sites, such as those near motorways and airfields, have requirements to reduce the noise impact on occupants. Homeowners also often expect this. Noise from plumbing, wastewater and sewage can also generate unwanted noise and while not specifically accounted for in the NZBC, consideration of this is important. 6 GIB TERRACE HOME GUIDE GIB TERRACE HOME GUIDE 7
Penetrations through fire and noise separations Penetrations in fire and noise walls are a significant area of vulnerability and where most problems occur. However, penetrations are easily dealt with through upfront planning and good communication. Designers, installers, electricians, plumbers and sprinkler installers should contact specialist passive fire protection suppliers and refer to their technical literature for fire collars, insulation and sealants when considering any work that would breach a fire wall. Some intertenancy systems, like GIB Intertenancy Barrier Systems for Terrace Homes, are designed to allow wall linings to be penetrated by plumbing services up to 65mm in diameter and electrical services penetrations not exceeding 90mm x 50mm. PLUMBING AND DUCTING Where possible, avoid running plumbing services in intertenancy walls. If running plumbing services in intertenancy walls is unavoidable, it is best to select an intertenancy specification with a central barrier. Check carefully whether plumbing penetrations need to be fire and acoustically sealed. Another option is to create a false wall to hold pipework off the intertenancy wall and maintain acoustic separation between units. See detail below left. ELECTRICAL Aim to locate electrical outlets within internal partition walls where possible. Mounting electrical outlets back to back should be avoided, unless an intertenancy separation with a central barrier has been selected. Where no central barrier exists, detail electrical outlets in intertenancy walls to have baffles or proprietary acoustic and fire rated flush boxes. Chase wall detail to avoid penetrations in intertenancy wall linings. Unit 1 Bathroom Chase walls Intertenancy Wall Bathroom Unit 2 right: A Speedwall intertenancy system installed on site. 8 GIB TERRACE HOME GUIDE GIB TERRACE HOME GUIDE 9
Other design considerations SECURITY Customer perception of security can be a consideration when selecting an intertenancy system as some prefer a secure separation in the centre of the intertenancy wall. For example, the GIB Intertenancy Barrier System has 25mm thick GIB Barrierline contained within galvanised steel GIB H-Studs as the central core. UNIT VALUE AND SALE PRICE Maximising the usable and saleable floor space within each tenancy is a priority for developers and as the footprint of the chosen intertenancy system will have an impact on the unit space; performance needs to be balanced against system cost. RAISE THE CEILING Particularly in dense residential living, using architectural features such as higher ceilings is a cost effective way to make smaller floor plates feel larger and create a better sense of value and quality of living for occupants. A minimum floor-to-ceiling height of 2.7m is suggested to gain more space as well as improve access to natural light and ventilation.* INTERTENANCY SYSTEM WEIGHT The mass of intertenancy walls is an important consideration for designers and structural engineers. Weight can impact on safety requirements and foundation design, particularly in seismic areas. GIB WARRANTY The builder is under a Building Act obligation to pass the warranty information on to the client at the end of the job. The easiest way to do this for GIB systems is to email the client a copy of the GIB warranty and our Care and Maintenance document, both available on the GIB website. THE RIGHT INTERTENANCY SYSTEM FOR THE SITUATION One intertenancy system may not be right for every terrace home. From low cost social housing to luxury terrace homes, there are variances in the level of performance and cost expectations. The following pages set out a range of intertenancy systems available, all of which can utilise GIB plasterboard as the interior lining. THE COST OF THE INTERTENANCY SPECIFICATION The breakdown of costs for each intertenancy system has been independently assessed by a third party Quantity Surveyor and aims to reflect the price tag of each intertenancy system, including all material components, labour, additional foundation design, equipment hire, sub trades and penetration design. SYSTEM Precast Concrete Masonry Autoclaved Aerated Concrete FUSSY DETAILS, SITE TOLERANCES AND ADDITIONAL TRADES ADD COMPLEXITY Tight sites often determine how the build programme is staged. For instance, tilt slab intertenancy walls require specialised lifting equipment and long lead times. Early discussions between the contractor and neighbours can be advantageous to ensure access. Complicated or fussy detailing can impact the project time frame and workmanship, and requires careful coordination and supervision of sub trades. Speedwall GIB Barrier System (average) GIB Double Frame (average) * NSW Department of Planning and Environment 0 Discussion Paper, Options for Low Rise Medium Density Housing as Complying Development, November 2015. GIB TERRACE HOME GUIDE 2000 Labour right: 10 TOTAL COST ($) Materials 6000 8000 Foundation Costing has been based on a typical multi-unit terraced house construction containing five, two story units with four intertenancy walls. Each wall was assumed to be 10m long x 5.70m high to the eaves with a 30 degree pitch forming a raking wall, and constructed with standard timber framing. Each Intertenancy wall area is approximately 71.00m2 with three electrical outlets each side of the intertenancy walls, i.e. 12 per wall. Terrace home under construction. GIB HELPLINE 0800 100 442 OR GIB.CO.NZ FOR MORE INFO 4000 10,000 12,000 14,000 16,000 Electrical The ground floor is a typical 100mm reinforced slab utilising a Rib raft system with specific design for heavier foundations required by concrete systems. There are no cantilevered soffits. The site is assumed to be within a 20km radius of the Auckland, constructed on a flat site, with soils of good load bearing capacity and excellent access. All rates include subcontractor margins. Compiled June 2016. GIB HELPLINE 0800 100 442 OR GIB.CO.NZ FOR MORE INFO GIB TERRACE HOME GUIDE 11
Comparing intertenancy systems Figures are a guide and for specific performance or technical information, contact the supplier. Higher performance can be achieved through specified design. Load bearing Double frame Barrier systems Concrete systems System GIB double frame systems GIB Barrierline Speedwall Typical autoclaved aerated concrete Typical concrete block Typical precast concrete Description Minimum footprint Noise performance GIB Double Frame STC rating 1 55 59, 2 60 64, 3 65+ 2 disconnected timber frames, with a minimum of 2 layers 10mm GIB Standard plasterboard 235 257mm GIB Barrier Line Central 25mm plasterboard barrier within a double frame timber wall, 1 2 layers GIB plasterboard either side. Galvanised steel-sheathed panels filled with lightweight concrete form a barrier between double timber frame walls, 1 layer GIB plasterboard either side. 280 300mm 188 321mm Lightweight concrete block central barrier within double timber frame walls, 1 layer GIB plasterboard either side. GIB Speedwall GIB Masonry 305 331mm Filled concrete block work, strapped and lined with 1 layer GIB plasterboard either side. GIB Precast 300 306mm Concrete tilt slab, strapped and lined with 1 layer GIB plasterboard either side. 260 310mm Fire performance Buildability considerations Installed as described in the GIB Installed as described in the GIB Installed as described in Additional subtrade Heavier foundations Heavier foundations Noise Control Systems literature to Intertenancy Barrier Systems for the Speedwall literature required. required, additional required, additional ensure performance. Terrace Homes literature to ensure to ensure performance. subtrade required. subtrade required, performance. crane/lifting equipment required, long lead times possible. Services Easy to design through Allows for penetrations up to 65mm Allows for penetrations up Allows small penetrations Allows penetrations Allows penetrations good planning. Plumbing diameter and 90mm x 50mm to 65mm diameter through through wall linings. through wall linings. through wall linings. services should be avoided rectangular through the wall linings the wall linings without The framed cavity can The cavity of a strapped The cavity of a strapped in intertenancy walls. without hampering acoustic or fire hampering acoustic or fire be used to accommodate wall can be used to wall can be used to performance. performance. services. accommodate services. accommodate services. Indicative weight Approx 45 65kg/m 2 54 65kg/m 2 70 90kgm 2 70 90kg/m 2 350 380kg/m 2 350 380kg/m 2 Source information gib.co.nz gib.co.nz Speedwall Intertenancy Systems 2016 for Terraced Housing and Apartments.speedwall.co.nz Supercrete AWS type 1 wall superbuild.co.nz RapidStak Mortarless Masonry for Intertenancy Walls firth.co.nz Various 12 GIB TERRACE HOME GUIDE GIB TERRACE HOME GUIDE 13
GIB Systems Winstone Wallboards Ltd offers a wide range of cost effective intertenancy GIB wall and floor/ceiling noise control systems. An overview of the most frequently used double timber frame and barrier systems has been included in this document. Each of these systems requires no specialist labour or equipment and they are compatible with GIB Aqualine Wet Area Systems and GIB EzyBrace Systems. A full list of intertenancy systems as well as associated detailing is provided in the GIB Noise Control Systems literature, the GIB Intertenancy Barrier Systems literature and on the GIB website. GIB Noise Control Systems have been extensively tested and independently evaluated and can be depended on to perform. However, specifications can be sensitive to component substitution. DOUBLE TIMBER FRAME SYSTEMS For technical guidance and construction details, see GIB Noise Control Systems technical literature. GBT(L)A 30a Double timber frame structure with studs at a maximum of 600mm centres and nogs at a maximum of 1350mm centres with 75mm insulation and two sheets each side of 10mm GIB Standard plasterboard. Noise / STC 58 Fire / FRR Indicative weight 45kg/m 2 245mm GBT(L)A 30b Double timber frame structure with studs at a maximum of 600mm centres and nogs at a maximum of 1350mm centres with 75mm insulation and two sheets of 10mm GIB Noiseline one side and one sheet of 10mm GIB Noiseline on the other. Noise / STC 58 Fire / FRR Indicative weight 45kg/m 2 235mm right: A GIB Intertenancy Barrier System under construction. 14 GIB TERRACE HOME GUIDE GIB TERRACE HOME GUIDE 15
GBT(L)A 60 Double timber frame structure with studs at a maximum of 600mm centres and nogs at a maximum of 1350mm centres with 75mm insulation and two sheets each side of 10mm GIB Fyreline plasterboard. GIB INTERTENANCY BARRIER SYSTEMS* For technical guidance and construction details, see GIB Intertenancy Barrier Systems, 2016. Noise / STC 60 Fire / FRR 60/60/60 GBT(L)AB 60a Double timber frame with GIB Barrierline central barrier. Studs at a maximum of 600mm centres and nogs at a maximum of 1350mm centres with 90mm insulation and two 10mm GIB Standard plasterboard each side. Indicative weight 45kg/m 2 245mm Noise / STC 68 Fire / FRR 60/60/60 Indicative weight 65kg/m 2 300 330mm GBT(L)A 90c Double timber frame structure with studs at a maximum of 600mm centres and nogs at a maximum of 1350mm centres with 75mm insulation and two sheets each side of 13mm GIB Fyreline plasterboard. Noise / STC 63 Fire / FRR 90/90/90 GBT(L)AB 60b Double timber frame structure with GIB Barrierline central barrier. Studs at a maximum of 600mm centres and nogs at a maximum of 1350mm centres with 90mm insulation and one sheet of 10mm GIB Noiseline each side. Indicative weight 54kg/m 2 257mm Noise / STC 64 Fire / FRR 60/60/60 Indicative weight 55kg/m 2 280 310mm GBT(L)A 90d Double timber frame structure with studs at a maximum of 600mm centres and nogs at a maximum of 1350mm centres with 75mm insulation and two sheets each side of 13mm GIB Noiseline plasterboard. Noise / STC 68 Fire / FRR 90/90/90 GBT(L)AB 60c Double timber frame structure with GIB Barrierline central barrier. Studs at a maximum of 600mm centres and nogs at a maximum of 1350mm centres with 90mm insulation and one sheet of 13mm GIB Noiseline each side. Indicative weight 65kg/m 2 257mm Noise / STC 67 Fire / FRR 60/60/60 Indicative weight 62kg/m 2 286 316mm 16 GIB TERRACE HOME GUIDE GIB TERRACE HOME GUIDE 17
GBT(L)AB 60d Double timber frame structure with GIB Barrierline central barrier. Studs at a maximum of 600mm centres and nogs at a maximum of 1350mm centres with 90mm insulation and one sheet of 13mm GIB Standard plasterboard each side. Noise / STC 61 Fire / FRR 60/60/60 Indicative weight 54kg/m 2 286 316mm * GIB Barrierline plasterboard is manufactured to Winstone Wallboards specific specification from a reputable overseas manufacturer. Beware of substitution The performance of GIB Systems are very sensitive to design detailing and construction practices. All GIB Systems have been developed specifically for New Zealand conditions and independently tested or assessed to ensure the required level of performance. It is important to use only GIB branded components where specified and to closely follow the specified design details and construction practices to be confident that the required level of performance and quality is achieved on site. Copyright Copyright Winstone Wallboards Ltd 2016. All of the material contained in this brochure, including all text, tables, charts, graphs, drawings, images, diagrams are protected by copyright. These materials may not be reproduced, adapted or transmitted in any form by any process, without the permission of Winstone Wallboards Ltd. Winstone Wallboards asserts its moral rights and reserves all other intellectual property rights in the materials contained in this brochure. For further information call our GIB Helpline on 0800 100 442. Interior of the Zavos Corner project in Wellington, designed by Parsonson Architects. 18 GIB TERRACE HOME GUIDE GIB TERRACE HOME GUIDE 19
FOR MORE INFORMATION VISIT gib.co.nz OR CALL THE GIB HELPLINE 0800 100 442