While most engineering questions and issues normally require an in-depth review of the situation and a tailored response that advises on the specific nature of the challenge, there are some questions – particularly in the domestic household environment – that are more common and can be answered in a general fashion.
Here, we share some of these questions and the typical responses we provide. Please note, however, that the information below covers domestic engineering for households, is generic in nature and provides general guidance and information only.
It should not be considered specific for any individual case.
Should you require further information or your problem is not of a standard nature, we strongly encourage you to call us to discuss it in detail.
Q: My house is cracked, what can Magryn & Associates do to help me?
A: Whenever contacted about a cracked house, our first priority is to send an engineer to site to view the house and the cracking. The engineer will then prepare a detailed report that covers:
- The extent of the damage to the house
- Any on-site factors that may have contributed to the problem
- Our professional opinion on the cause of the cracking
- Our professional recommendations on what is required to address and solve the problem
As underpinning is a very expensive remedial exercise and should only be carried out as a last resort and in severe cases, Magryn & Associates engineers will always first look for and consider other appropriate solutions.
All fees for this work are time-based and charged at our rate of $225 per hour plus GST. Using a typical suburban Adelaide home as an example, the evaluation and recommendations captured in the report tend to cost in the region of $1,050 plus GST if no underpinning is recommended. Where underpinning is involved, the report costs about $1,550 as there is also a need to investigate the site soil and prepare an underpin design. As at November 2020.
In more complicated cases, we might also be required to conduct a floor level survey inside the house. While the advanced Technidea zip level we use provides us with a quick and highly accurate reading of the sloping floor, the survey is at some additional cost.
The detailed report then specifies the work to be done, which you can pass on to building contractors and request a quote to attend to the work.
Please note that Magryn & Associates cannot guarantee that the work undertaken will prevent all future cracking or movement as a combination of one or all of Adelaide’s soil types, the footings in place and the type of house construction may contribute to an ongoing problem.
Rather, we are attempting to reduce the extent of the cracking and movement, eliminate instances of wide cracks of a structural concern, and achieve a more manageable ‘patch and paint’ solution,
Q: What is better…traditional concrete underpinning or chemical injection such as Uretek?
A: It’s very much ‘horses for courses’ as each has its strengths and each is better in some situations than the other.
Traditional concrete underpinning can go down as far as required and given that the upper 3.5m of Adelaide soil tends to expand and contract as the seasons change, we typically specify that it is extended down to at least 4m. By founding the underpin below this shifting layer, we’re able to provide a more stable footing for your house.
As chemical underpinning typically extends down to about 1.5m and is therefore founded in the shifting soil layer, these underpins – along with the soil around them – may be susceptible to heave or settlement over time.
We therefore tend to specify traditional concrete underpins around the outside of a house.
However, chemical underpins remain the preferred method in instances where there is no seasonal moisture change, such as under a separating party wall between two maisonettes or under a warehouse slab. The chemical injection underpins are also much less intrusive to install – for starters, you don’t need an excavator occupying your hallway! – and provide very good control when lifting a footing.
Q: Can you lift the house and close the cracks?
A: Jacking of the house off the new underpins involves placing a jack between the top of the new underpin and the underside of the house footing. The jack then lifts the building, steel wedges are installed and when the jack is removed, the wedges are permanently grouted into place.
This allows the edge or corner of the building to be lifted and in the process, close or partially close some of the cracks.
It is important to remember that jacking is not always possible, especially in cases where:
- There are bluestone footings which are not structurally strong enough to withstand jacking and will break
- The concrete of the footing may be too weak
- The footing may be too deep and the soil too clayey, its suction preventing any lifting of the footing.
You also need to be aware that there is always a danger that jacking may lead to cracking in other areas where it had not previously occurred.