GOLDEN RULES THAT’LL HAVE YOU BUILDING BETTER WITH TIMBER
Here are our guiding principles for designing and delivering successful timber and hybrid buildings.
RULE #1
Start with Early Collaboration
It all begins with an idea. Maybe you want to launch a business. Maybe you want to turn a hobby into something more. Or maybe you have a creative project to share with the world. Whatever it is, the way you tell your story online can make all the difference.
RULE #2
Design the Right Grid
Don’t try to “shoe-horn” an engineered timber building into an inappropriate grid layout – grid spacings for steel and RC multi-storey structures typically do not always result in economic or efficient mass timber designs. Start with grid spacings that suit either material.
RULE #3
Coordinate Fire, Services & Structure Early
It is critical that the architect(s), structural engineer(s), acoustic and fire engineer(s) and building services engineer(s) coordinate design activity early in the design process. Whilst structural engineers can accommodate specific member and sizing requirements specified by the fire engineer (and any differences there may be with structural requirements), it can be costly and inefficient if the fire design is not completed until very close to consent submission. Similarly, prohibitive service clashes can result in construction delays, significant cost overruns and large numbers of contract variations. BIM modelling is crucial.
RULE #4
At concept and feasibility stage, the quantity surveyor needs to have had some experience with costing mass timber builds. Many quantity surveyors haven’t had that experience. This can result in very high contingency cost estimates being imposed on the mass timber option versus reinforced concrete or steel options. Once mass timber “goes off the table” at any early stage it is typically never reconsidered as it becomes more costly to do so as the stages of design and specification progress.
Use an Experienced Quantity Surveyor
RULE #5
Compare Options Early and Fully
Carry out early cost, mass and greenhouse gas emissions estimates and comparisons between timber, steel, reinforced concrete, mass timber and hybrid options (a combination of materials). It’s critical that total out-turn cost estimates for all options are developed and compared. Many of the benefits of a mass timber build are derived through construction and on-site aspects, including:
a. Rapid construction times – up to 30 percent faster, reducing funding costs.
b. No need to wait for the concrete to set.
c. Lower preliminary and general costs as a result.
d. Greatly reduced onsite wastage.
e. Significantly improved health and safety, and quicker and simpler installation of temporary fall protection systems.
f. Fewer truck movements and less noise and disturbance to the surrounding community.
g. Rapid first-fix of many services due to ease of fixing to timber members.
h. Lower capacity and low-cost cost and duration crane and lifting equipment required due to timber elements being lighter than steel and reinforced concrete.
i. Significantly earlier handover of the building to the asset owner, enabling lower time cost of money, better and earlier return on investment and earlier user occupation.
RULE #6
Optimise Foundations for Timber’s Light Weight
Carry out foundation designs early. Mass timber and hybrid builds tend to be significantly lower mass compared with reinforced concrete and or steel options. Reduced mass typically results in smaller, reduced-cost foundations and/ or earthworks. Alternatively, the ground’s carrying capacity can result in more floors and Gross floor Area with mass timber’s weight advantage.
RULE #7
Assess Ground Conditions Early
Get geotechnical assessment done early. The existence of poor or restrictive soil conditions can be cost-effectively addressed through the selection of mass timber or timber hybrid design and construction.
RULE #8
Engage Contractors in Early Design
Ensure the design team engages with contractors very early in the process. Experienced contractors have a lot to offer regarding cost-efficient design and construction sequencing. Certain contractors now have good experience with mass timber construction.
RULE #9
Plan for Moisture and Fire On Site
It’s critical that the contractor prepares and adheres to a mass timber moisture management plan. Truck supplies and timing, site storage, construction sequencing, and moisture content monitoring in members and panels must all be considered early on. These need to be factored into design and total out-turn costing. A plan for potential construction site fires and mitigation must also be prepared and followed. Consider factory-applied weather membranes, end sealing or covering member ends, taping joints in floors, tarpaulin use to repel rain, and brooming paths for any rain that does make it through. Specify mass timber made from feedstock treated to NZ Standards.
RULE #10
Procure Smart and Early
Engage early mass timber and other material suppliers. Cost-efficient designs use standard panel thicknesses, member spans and, where possible, connection systems. Elaborate or complicated steel connection systems can add significantly to the total out-turn cost of a mass timber or hybrid build. Early procurement is critical as it minimises or eliminates delays in supply and keeps the erection programme on track.
RULE #11
Engage with Consenting Authorities Early
Engage early with the relevant Territorial Authority (Consenting) with a specific focus on and discussion of:
a. Proposed approach to meeting the requirements of Building Code clause D - durability.
b. Proposed approach to meeting the requirements of Building Code clause C - fire safety.
c. Proposed approach to meeting the requirements for building evacuation, if relevant to the size and building usage type.
RULE #12
Promote Timber’s Value to Developers
Talk to developers and prospective building owners. Leading developers are increasingly recognising the commercial premium and reputational benefits of high-quality mass timber buildings. International research shows that people like living and working in these buildings because of the proven health and wellbeing benefits provided. Once a project starts on site, the mass timber can be consumed very quickly. As such, mass timber suppliers need time to produce a buffer stock so as to keep up with site teams.
RULE #13
Don’t Delay Shop Drawing Sign-off
Ensure design teams are carefully managed to sign off shop drawings on time, so as to be ready for manufacture in the window available, and not shorten the suppliers’ production period.