DOES MY FOUNDATION NEED ENGINEERING?
A question we are often asked here at QPOD™, New Zealand has a wonderfully vast choice of terrain having been blessed with such a natural playground right our backdoor.
This comes with challenging soil structures, varying strata’s and dozens of acting factors that impact the site we choose to build our dream home on.
Our most commonly encountered ground challenges come from liquefaction, poor bearing and expansive soils, or any combination of these, all of which QPOD™ is a great solution for.
QPOD™ is a Branz appraised and CodeMarked foundation choice when used in accordance with Allied READY Superslab and the parameters within this design manual are met. This means your architect can specify Superslab with QPOD™, with no engineer input necessarily in the foundation design, a great saving. Outside of this we refer to the design as S.E.D. (Specific Engineered Design). Any engineer can incorporate the QPOD™ system into your ground condition scenario, this is also a service offering we offer at QPOD™, see Services.
So, what is my site then? Let’s unpack what your site might be starting with some of the parameters out of the CodeMark system:
Designers need to understand and adhere to the conditions and limitations as outlined below. If in doubt, please check with Allied Concrete for advice on your Allied Superslab project.
Building types and loading suitable for the
Allied Superslab System
The Allied Superslab has been designed to support timber framed residential houses generally satisfying the requirements of NZS3604 and as detailed in the manual. The verification of the compliance of the design with this document is the responsibility of the designer and shall be confirmed by the building control authority issuing the building consent. Items 1-6 shall be verified by the designer. Refer to check list procedure in section 7 of the manual for further guidance.
READY SUPERSLAB TECHNICAL MANUAL
- SOIL CONDITIONS – Buildings founded on ‘good ground’ as defined by the New Zealand Building Code (B1) andNZS3604. This is summarized in section 3.2 of the manual.
- HOUSE SIZE – Total area of 300m2 or less. No more than two storey timber framed buildings with max height of 10m (toapex). Maximum length of 30m unless detailed with free joints in accordance with this manual as per figure 21 and 33. The foundation needs to be a regular shape with a minimum area (m2) to perimeter (m) ratio of 1. Irregular shaped foundations need specific engineering input and are beyond the scope of this document. Refer Table 2 below for guidance on shape requirements.
- MAXIMUM SPAN AND HEIGHTS – Maximum Roof span of 12m, first floor joist span of 5m, and maximum storey height of 3m (Cladding combinations as per table 1 and building types A-E)
- BUILDINGTYPE – Importance level 1 and 2 structures as per NZS1170 and NZS3604 – Standard residential house
- WEIGHTS – Permanent (gravity) and imposed (live) loads as defined in section 3.4 – The foundation system is designed to accommodate a standard residential house generally as defined in NZS3604:2011 and defined in section 3.4
- WIND AND SEISMIC LOADING – Maximum wind loading of Extra High as per NZS3604:2011 and maximum seismic hazard factor (Z) of 0.45 and soil classes A-E as per NZS1170. Also, refer section 3.4
S.E.D Specific Engineered Design
After looking through the Superslab manual you might have found your house project falls outside the CodeMark parameters, don’t worry you are not alone, much of New Zealand’s ground is now requiring engineered foundation designs. At QPOD™ we set out to make this as easy as possible, it may be only slightly outside of CodeMark or well outside, either way we set out to make it a seamless affordable process.
QPOD™ std detailing can be downloaded from our resources page or directly here: QPOD™ std detailing for Raft.
From here your engineer can add the additional design and strengthening elements required to meet your house design.
Your engineer too busy? Haven’t we all heard that before, let us take it from here, head on over to our services menu to purchase an engineered design package from the experts. At QPOD™ we take your home project seriously; our services provide a fully engineered foundation design and PS1 for council consent submission. What we need from you, it’s all laid out on the services page but essentially just your plans, truss design and Geotech report, these three elements are fundamental for us to proceed with a design.
There are many other influences and factors in an engineered foundation design, we encounter new situations everyday.
For more information on ground condition types and different engineered solutions see our full blog on this here: S.E.D QPOD™ Foundations
Get in touch with a foundation specialist today: