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Frequently asked questions
  • What is the difference between Uglie, SED, UniLog and MultiPole poles?

    Uglie poles are debarked rather than peeled. This leaves a rougher finish from the natural nodal swellings along the pole. By debarking, more of the wood’s natural strength is retained. The rough surface is also ideal for Ground Improvement as it allows the pole to interact better with the surrounding soil.

    SED poles are peeled while still retaining the natural taper of the log. The peeled finish is ideal for Deep Piles as it minimises negative skin friction from the surrounding soil.

    UniLog poles are machined to a uniform diameter, resulting in a very consistent machined finish. This uniformity makes them suitable for Raft Foundation components, such as bearers and jack studs. It also allows brackets to be easily designed for the pole as the diameter is accurately known.

    MultiPoles are any of the Uglie poles, SED poles, or UniLog poles, but with a hollow-core.

    Each of these pole types can be treated to H5 (or H6 for marine applications) and produced from high density Radiata pine.

  • What does SED mean?

    Small End Diameter. It is the industry standard for grading timber poles. Due to the natural taper of the pole (average of 6mm/m) there will always be a small end and a large end with different diameters.

  • Why is there a hole in the MultiPole?

    The hole is made by removing the corewood from the pole. Corewood doesn’t provide any structural strength to the pole, so removing it doesn’t reduce the strength of the pole.

    The hole allows treatment preservative to penetrate the pole from both the outside surface and from the inside, giving full penetration of the pole, which in turn increases durability.

    The hole allows the pole to shrink over time as it dries, while minimising the checking that can occurs along its length – this is very useful for visual applications.

    The hole also allows multiple pole lengths to be joined together using MultiPole Connectors (simple pin connectors) to achieve required depths, as opposed to handling extremely long poles supplied in a single piece. This is especially useful where the required depth is not accurately known, or where there is restricted space to work within. Poles can be joined until the required depth is reached. The ability to join poles also reduces waste.

    The hole significantly lightens the pole. This allows trucks and rail wagons to carry much greater loads of poles at a time, with limitations being based on volume rather than weight, which is often the case with solid poles.

    The hole can house a water jetting nozzle and hose to enable water jetting during installation, and can prevent hydraulicing during pile driving.

    The hole allows structural components made from the poles to be post-tensioned with a reinforcing rod through the core.

    The hole can also be filled with concrete to provide a composite element, with the strength and ductility of the outer wooden layer combined with the strength of the concrete core.

    The hole can be used to grout a reinforcing rod down the pile to tie it to a slab or other structural components above.

  • Why are SED poles used for deep piles?

    The peeled surface of SED poles minimises the negative skin friction of the surrounding soil on the pile.

    During a seismic event, liquefiable soils tend to settle. As they do, they pull downwards on anything that is within the soil, such as a pile. This is called negative skin friction. When piles experience too much negative skin friction they can buckle, break, or fail in other ways. When a pile has a smooth surface, negative skin friction is minimised. The pile’s smooth surface reduces the grip that soil can have on it, thus reducing the soil’s ability to pull the pile down.

  • Why are Uglie poles used for ground improvement piles?

    Improving the ground relies on interaction between the soil and piles to stop the soil from liquefying during a seismic event. The rough surface of Uglie poles maximises their interaction with surrounding soils. Uglies have increased skin friction.

  • What is a PS1/PS2/PS3/PS4 and when are they needed?

    PS stands for Producer Statement. These are documents that the professionals working on your project will supply at various stages along the way.

    A PS1 accompanies a specific design by an engineer.

    A PS2 is a peer review of an engineer’s design. For most residential designs it is not needed. Also note that specific designs by engineers are not automatically required to be accompanied by PS2 documentation.

    A PS3 is provided by the contractor that completes the work on site.

    A PS4 is a construction review by the engineer, and is carried out during construction. Commonly referred to as "engineers sign off,” it indicates that the engineer is happy with how the installation was carried out by the contractor. It normally involves one or more site inspections by the engineer during construction and possibly verification testing of some sort (E.G. testing pile sets).

  • What is the difference between testing pile sets, PDA testing and static load testing?

    Each of these methods is a way for an engineer to test the load capacity of the piles during construction. This enables the engineer to verify that piles are meeting the loads required by the design. These methods vary in accuracy and cost.

    Testing pile sets involves dropping a weight onto a pile (E.G. 1000kg weight with a 1.0m drop) and measuring the sets (how far the pile moves with each blow). Generally the sets are in the region of 5-20mm, but this can vary according to each site. The Hiley Formula then enables an engineer to calculate the load capacity based on the pile sets. Testing pile sets in this manner is generally acceptable for residential buildings.

    A Pile Driving Analyser (or PDA) is an electronic device that has sensors which are mounted on the pile being tested. When a weight is dropped on the pile (similar to testing pile sets) the PDA tester assesses the load capacity of the pile. PDA provides more accuracy and information than the Hiley Formula, and is generally used on commercial buildings.

    Static load testing involves placing a lot of weight on the pile being tested, then measuring how far the pile moves at specified intervals over several hours.

  • How much lateral movement can timber piles be designed for?

    300mm. For sites with more than 300mm lateral movement, an in-ground retaining wall may be considered to reduce the lateral movement to within the threshold of timber piles.

  • What are my foundation options for a concrete floor?

    If a suitable bearing layer is identified (of sufficient hardness and thickness), deep piles are suitable. An enhanced slab should be designed to be supported directly on top of the piles. If the site contains sloping ground and/or elevated floor level requirements (due, for example, to flood levels) then a suspended concrete slab is an option.

    Alternatively, a ground improvement system using timber piles can be designed to improve the ground to TC2 levels. On top of the improved ground a load transfer platform can be constructed, followed by a TC2 waffle slab.

  • Do you construct concrete slabs?

    Not usually. If we have to we use a concrete layer, so it is always more economical if they work directly for you.

  • What are my foundation options for a timber floor?

    If a suitable bearing layer is identified (of sufficient hardness and thickness) then Deep Pile Foundations are suitable. Alternatively, a Raft Foundation (which is equivalent to a Type 2B surface structure, but requires 100kPa or less with specific design) is usually suitable.

    Bearers and joists can be designed to sit above either of these foundation types. These can be in accordance with NZS 3604, or according to specific design.

  • Do I need to adhere to the foundation recommendations in the geotechnical report?

    No. A geotechnical report is very useful as a factual report of the ground conditions, and the recommendations within the report are useful to provide some guidance. However, they are just recommendations and an engineer who performs specific engineering design for a foundation, along with an accompanying PS1 and justification for their foundation, is the one who signs off and takes liability for that design, not the author of the geotechnical report.

  • What Technical Categories (TC) of land are timber piles suitable for?

    TC1, TC2, and TC3, with specific engineering design.

    TC1: Future land damage from liquefaction is unlikely, and ground settlements from liquefaction effects are expected to be within normally accepted tolerances.

    TC2: Liquefaction damage is possible in future large earthquakes.

    TC3: Liquefaction damage is possible in future large earthquakes.

    These technical categories are intended to guide foundation choice pathways that owners, insurance companies, the EQC and their respective Project Management Offices (PMOs) can use. They are a starting point for assessing a particular site in order to determine the appropriate foundation solution for each site.


  • What does TC1/TC2/TC3 relate to?

    The expected level of land damage following a future seismic event (TC1 expecting the least damage through to TC3 expecting the most damage). Subsequently, the level of engineering required for new foundations in each of these categories increases.

  • Can TC3 solutions be used in TC2 or TC1 land?


  • What verification testing of the soil is needed following ground improvement?

    Subject to how the design was carried out, the verification testing can vary from nothing (if the engineer is satisfied after watching some of the piles being driven), to geotechnical tests such as Cone Penetration Test or Dilatometer testing after all the piles have been installed.

  • What treatment level is required for poles near water?

    For poles in the ground, even close to a river or ocean, and below the water table, H5 treatment is sufficient. For poles in a marine environment, such as a jetty exposed to salt water or estuarine ground, H6 is required.

  • How do timber piles compare to concrete and steel (screw) piles?

    Screw piles are only end bearing and have to find a thick end bearing layer to embed into. They also have limited capacity for lateral restraint. Concrete piles also need an end bearing layer to embed into. Concrete poles are very stiff and can be too stiff under earthquake loads. Timber poles are flexible - they can be end bearing or reliant on skin friction, but can also work with both. Timber poles are flexible laterally when it comes to earthquake loads. Installation equipment for screw piles is generally very large as a huge amount of torque is required for installation. Also machine is liable to slew around given that it is trying to rotate (screw) the pile into the ground. Concrete piles are heavy and again require large equipment. The operational/working area needs to be able to accommodate the equipment and the piles. Timber poles can be installed using smaller, lighter footprint equipment.

  • How do you know what foundation system to use?

    The geotechnical report provides most of the information as to what our options are or are not, along with a few extra details such as the desired floor type (timber or concrete) and floor level requirements due to flooding.

  • Can you organise a geotechnical investigation and provide me with a geotechnical report?

    Yes, get in touch with us today and we’ll get things started.

  • Can you provide a free estimate or a quote for my foundation repair or rebuild?

    Yes, get in touch with your information.

  • Can you design/supply/install timber retaining walls?

    Yes, get in touch with us today and we’ll get things started.

  • Who do you normally work with?

    Anyone who needs a foundation solution for difficult ground - from government departments, to building companies, to insurance companies, and other parties.

  • How do you get poles into the ground?

    For most Ground Improvement and Deep Pile Foundations, we use a specialised high frequency vibration system. Our contractors use custom-built machinery that operates at an exceptionally finely tuned frequency. This method ensures minimal product damage, and doesn’t disturb neighbouring properties. Our installation methods range from high frequency vibration, pile driving, to proprietary raft foundation installation equipment.

  • Do you water jet poles into the ground?

    We can do if required. However, we do most of our jobs with high frequency vibration as it is fast, efficient, and leaves surrounding properties undisturbed.

  • Do you only do commercial work?

    No, we do both commercial and residential foundation work, although our specialty is in more complex, commercial developments, including bridges and retaining walls.

  • We are looking at a complicated solution for the design of retaining walls, piles, and floor systems. Can you help us?

    We sure can – get in touch with the information and we can take it from there.

  • What health and safety processes do you follow when you are on site?

    A Site-Specific Safety Plan (SSSP) is produced for each site following a check of all hazards applicable to each site. If we are working as a subcontractor on someone else’s site we will follow the safety processes they have in place in addition to our own.

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