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Structural engineering of swimming pools in Perth - a comparison of concrete vs fiberglass

Updated: Feb 8, 2019

Building your dream swimming pool will require design excellence and engineering expertise to assess a wide range of options and considerations. In Perth, in-ground swimming pools are most commonly constructed from reinforced concrete of fiberglass. Each material has its advantage and disadvantage and choosing between them becomes a question of picking the best construction method for your budget and the particular site requirements. There are different types of swimming pools and the most common pool styles are plunge pools, free-form pool, geometric pool, lap pool, diving pool, infinity pool and the perimeter overflow pool.


In this article, we will focus on some of the structural engineering design consideration, a brief comparison of concrete & fiberglass swimming pools and we will also touch on the swimming pool inspection requirements as applicable in Perth, Western Australia.


SO WHAT IS INVOLVED IN THE STRUCTURAL DESIGN OF A SWIMMING POOL?

A swimming pool builder or architect will usually employ a structural engineer to insure that the loads being exerted on the pool’s concrete or fiberglass shell can withstand the expected loads. Different soil textures encountered in Perth, proximity to building foundations, toe and heal hillsides locations, subsoil strata composition, seismic zone proximity, hydro-static water conditions and a host of other site specific conditions may exist. An essential component to swimming pool design in Perth can involve reviewing the results of the geotechnical report (test borings, soil sampling, etc.), which in turn will direct the prescribed remedy for directing the structural engineering application. If the proposed site contains a number of retaining walls, services and other buildings, the structural engineer should conduct a site inspection before finalising the engineering details.

Prior to submitting your building application, the structural engineer should determine the location of any Water Corporation assets that exist on the property involved. Sewer reticulation pipelines (which typically includes sewer pipelines that have a diameter of 300mm and smaller) are the most common type of asset found in private property. Occasionally sewer mains, sewer pressure mains, water supply pipelines and stormwater drains are also found.


If an asset is found close to your proposed swimming pool, and you have exhausted all options to relocate the proposed structure, a structural engineer is required to provide a piling detail which will:

  • isolate the asset from excessive loading from your proposed swimming pool, building or structure;

  • allow safe access to the asset for inspection, maintenance and repairs;

  • provide structural support to protect your proposed swimming pool from the risks of asset bursts and failures.

Another important consideration is the specification and installation of a hydrostatic relief valve. If the ground water rises to an elevation higher than the level of water in an in-ground pool, hydrostatic pressure can adversely affect the swimming pool structure. In the case of concrete or other swimming pools, where exterior hydrostatic pressure becomes excessive it can disrupt the integrity of the swimming pool structure through shifting or dislodging of the wall and/or the swimming pool floor. This pressure can also cause the swimming pool to actually raise out of the ground. Therefore consideration for hydrostatic valve(s) is a crucial requirement.


SO WHAT IS THE USUAL PROCESS FOR OBTAINING A BUILDING PERMIT?

According to the Department of Mines, Industry Regulation and Safety, prior to a building permit being granted in Perth by a permit authority (usually the relevant local government), a registered building surveyor is to to confirm that the proposed swimming pool and its safety barrier comply with the relevant building standards. This is accomplished by signing and providing a ‘Certificate of Design Compliance’ (CDC).


The applicable building standards will ensure that the swimming pool meets certain criteria pertaining to:

  • structural adequacy of the swimming via certified engineering drawings;

  • water re-circulation system;

  • energy efficiency requirements if swimming pool heating is installed;

  • water efficiency via inclusion of a compliant pool blanket;

  • safety barrier and relevant cosiderations.

In Perth, anyone can apply for a building permit, the owner, pool builder or barrier installer. You may choose to submit either a certified or uncertified application for a pool and its safety barrier. The difference is explained below:

  • A certified application (Building Commission form BA1) is submitted to the relevant permit authority and the CDC is also attached. An independent building surveyor is appointed to certify that he plans and relevant specifications are adequate. The relevant permit authority (local council) has 10 business days to decide on a certified application.

  • An uncertified application (Building Commission form BA2) is submitted directly to the local council or Shire without a CDC. The local council or Shire will engage an independent building surveyor to review the proposal and to provide the CDC. The permit authority has 25 business days to make a determination on an uncertified application.


CONCRETE SWIMMING POOLS

The concrete pool pool, is a very popular type of construction method in Perth. Structural reinforced concrete allows for virtually any design or shape you can think of and is an extremely durable option. Depending on the exact type of surface finish, this type of pool may required to be re-surfaced throughout its lifetime.


It is likely that with adequate maintenance, concrete pools will last longer than fiberglass pools because of the materials used and construction methods. When maintained regularly and cleaned, a concrete swimming pool can last for several decades. It is essential however that a quality surface finishing product is used to seal the concrete as this will greatly improve the durability.


In most cases, a fiberglass swimming pool will last between 25–30 years, and in some cases the pool finish may need to be reapplied every 10 years. These fiberglass swimming pools are somewhat less durable than concrete partly because they do not use the same reinforced construction methods. Generally, the swimming pool shell is installed on top of concrete or sand pad, making it prone to cracking if the foundation moves outside expected tolerances.


The choice and flexibility of concrete pools is virtually unlimited. If the aim is to create a customized pool that can work with size and shape of your space, a concrete swimming pool will be worth considering. Features like rocks, fountains, and grottos can be easily constructed into the design of your swimming pool to seamlessly integrate into the surrounding landscape.


FIBERGLASS SWIMMING POOLS

Fibreglass pools are typically manufactured in a factory and leave that factory fully ready to be installed in the ground as a single large pool shell.  This type of material has a very durable surface that doesn’t need much maintenance and can be actually be repaired in the event of a crack or puncture.


Some of the advantages enjoyed by fiberglass pool owners include a short installation time and very little maintenance requirements. The coat of the surface inhibits the growth of algae making it easy to keep sanitized. Typically, the lifetime cost of a fiberglass pool is considerably lower than a concrete pool. One potential limitation is related to the shape and size of the pool. Because fiberglass pools come pre-fabricated and travel to potential locations by truck, consumers are limited to the shapes offered by the manufacturer. It is however possible to arrange for oversize load permit with Main Road WA.


Perhaps the main disadvantage of a fiberglass swimming pool in Perth is the limited size and design choice when compared with a concrete swimming pool  


SWIMMING POOL INSPECTION REQUIREMENTS

When building a new swimming pool in Perth, it is important to have a qualified structural engineer to carry out inspections during critical stages of construction, including:

  • just after the steel reinforcement has been installed it is best to have an engineer confirm via a written report that the steel reinforcement has been laid according to the structural engineering specification;

  • after all construction works have been completed.

It is expected that site specific requirements have been addressed during design such as surcharge forces due to adjoining buildings, effect of excavation on existing buildings and effect of construction of the proposed pool on existing services. After the inspections are carried out, a report should be issued to satisfy the requirements of the development conditions.


If you notice some developing problems in your existing pool such as tile cracking or losing water, a structural pool inspection would determine the cause of the problem and determine what remedial works are required and also consider the immediate safety of the pool.


Whether you have an above ground, in ground, residential or commercial pool, under construction or in need of renovation, our team of structural engineers have the knowledge and experience to provide structural pool inspections to maintain quality of the newly constructed pool or appropriate advice and recommendation for the renovation of the existing pool.


As a final note, while the responsibility is on the owners of the property for ensuring that any safety barrier restricting access to a swimming pool is maintained and operating effectively at all times, there is no other option than to supervise young children around the swimming pool. If you are purchasing a home in Perth, it is essential to obtain a thorough pre purchase building inspection to see whether the swimming pool is in working order or needs any repairs. Blog image courtesy of callstevens.com.


If you have any questions, get in touch with us to discuss your requirements and to obtain a free quote.

Rotaru Building Consultants

send us an email

call us: +61 402 666 702

visit our website: www.rotaru.com.au

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