New building or extensions
Joshua Wong has personally been involved in over 250 building design projects (including his previous employment as well as Cephas Rock Limited). The structural engineering jobs range from ordinary standard houses, multi-unit apartments up to high end architectural designed houses in Christchurch and Canterbury.
Some of these homes have been designed by well-known architects such as: Andrew Patterson, Peter Beaven, Darren O’Neil and Don Donnithorne; and architectural designers such as: Allan Pritchard, Mark Walters and David Barker.
Generally the design process includes the following:
- Shallow soil investigations and reports
- Meeting with house owner and architect to define the needs and goals
- Structural concepts design
- Structural model and analysis with 2D and 3D software eg Space Gass or in house design spreadsheet
- Structural member design to complied with New Zealand Standards
- Counter check to ensure all the member sizes are compatible with architects’ design
- Connection details
- Structural drawing
- Documentations for building consents
- Liaise with local authority to obtain the building consent
- Site inspection to ensure the work is carried out in the accordance to the plan and specifications
Shallow Soil investigation and reports
Cephas Rock Limited provides soil testing alongside our structural engineering services. We can determine the soil conditions for your site and assist you with your foundation design.
A shallow soil test report includes the following:
- Scala penetrometer tests (DCP) to determine the soil bearing capacity down to 3 metres below ground level or until test refusal
- Hand auger (HA) bore holes to determine the soil profile
- Check the water table level
- Estimate the soil bearing capacity
- Foundation recommendations
- Visual observation for any evidence of land damage e.g. liquefaction, lateral spreading, fissures etc.
This is a shallow soil test which involves hand auger and penetrometer tests to 2-3 metres deep. This is especially suitable for Christchurch land zoned Green: Grey TC1 or Yellow TC2. Also, should it be necessary, we will provide a site specific foundation design (see below)
Please note, this test is not suitable for TC3 zones. For this you will require a full site-specific deep geotechnical report and specific foundation design
Further information is available on the Ministry of Business, Innovation and Employment (MBIE) website
Deep Geotechnical investigation and reports
A deep geotechnical investigation report may include the following:
- Desktop study of soil logs provided and other information sources such as the Canterbury Geotechnical Database (CGD)
- Geotechnical site walkover survey and co-ordination with ground testing contractors
- Interpretation of cone penetrometer tests with pore pressure measurements (CPTu), or Dynamic Probe Super Heavy tests (DPSH-B) up to 20 metres below ground level
- Liquefaction assessment including ground surface settlement estimations
- Foundation recommendations for repairs or new build
- Statement of professional opinion on the suitability of land for subdivision (Hazard assessment according to Section 106 of the Resource Management Act (1991))
- Site observations during construction stage
This is suitable for Christchurch land zoned Green: TC3. Also, should it be necessary, we can provide a site specific foundation design.
Specific Foundation design
This service is provided for TC1 properties only if the soil safe bearing capacity is less than 100Kpa (ultimate bearing capacity of 300Kpa).
For TC2/TC3, we can provide site-specific foundation design to suit your requirements.
Structural assessments
Since 4th September 2010, Cephas Rock Limited has been in great demand for structural assessments of buildings all over Canterbury.
We are engaged by many home owners, buyers and sellers to fulfil insurance and banking needs by providing home and property assessment reports.
Top staff and equipment
We have invested heavily in our staff by sending them to courses and seminars as well as on-the-job training. We use the best equipment that we can possibly get for our engineers. One of the many tools we use is the Zip pro 2000 and digital spirit level to measure the floor levels.
A structural assessment report would generally include the following
- Describe the building construction era and its material
- Report on all the structural damage we can possibly see
- Analyse the issues to determine if they are of structural concern
- Advise on structural repair methods and solutions
- Report on the physical ground’s condition e.g. evidence of liquefaction, lateral spreading etc.
- Monitor the structural repairs during construction stage
- Report on structural repairs and provide engineering “sign-off” / producer statements
Detailed Seismic Assessment (DSA)
Following the recent Canterbury earthquake sequence, the territorial authorities (TA) now requires all non-residential buildings, including multi-unit residential blocks, to obtain a detailed seismic assessment (DSA).
The aim of the evaluation is to assess the damage that the subject building sustained from the seismic events, and to determine if the building is defined as earthquake prone in terms of the Building (Earthquake-prone Bulidings) Amendment Act 2016, taking effect from 1 July 2017.
Part of the evaluation is to assess the likely seismic (earthquake resisting) capacity of the building, expressed as a percentage of the New Building Standard (%NBS).
Buildings with %NBS less than 34% are considered potentially earthquake prone and seismic strengthening or demolishing will be required within the set time frames.
Buildings with %NBS between 34% and 67% are considered unlikely to be earthquake prone. However, mitigation or improvement of any critical structural weaknesses is recommended, but not mandatory by current legislation.
Buildings with %NBS over 67% are considered unlikely to be an earthquake risk and no further action is generally required by current legislation.
A DSA generally consists of 3 stages. In some cases it may be immediately obvious that stage 2 or 3 is required and so the preceding stage(s) may be omitted or combined.
Stage 1 – Qualitative assessment (Initial Seismic Assessment)
A visual non-invasive inspection of the building is carried out. An estimate of the seismic capacity is obtained using the Initial Evaluation Procedure (IEP) developed by the New Zealand Society for Earthquake Engineering (NZSEE). No detailed calculations are carried out at this stage.
Stage 2 – Quantitative assessment (Detailed Seismic Assessment)
If required, detailed analysis may be carried out to more accurately assess the %NBS. In the absence of reliable plans and drawings, invasive testing such as opening lining or exposing reinforcing steel may be required. Geotechnical engineering input may also be required.
Stage 3 – Seismic Strengthening design
Buildings found to have %NBS under 34% after the Stage 2 assessment generally require strengthening or demolishing under current legislation. The type and amount of strengthening depends on factors such as building size, construction, %NBS achieved, etc. We note that local authorities policy and NZSEE guidelines recommend strengthening to more than 67%NBS.
Contact us
Please email admin@cephasrock.co.nz if you would like to discuss any engineering project.
