Yet, if you’re a Melbournite affected by slab heave, it is of little comfort to know that you are not alone.
Slab Heave in Sydney
There’s been a spike in users from Sydney hitting our website looking for information about slab heave. Welcome – and don’t panic! There’s plenty of information on the web about slab heave and how you can minimise its effect. I hope we can help provide some of that information for you.
Melbourne, Sydney and Brisbane homeowners – if your house is within the builder’s warranty period, the builder and the developer are responsible for fixing slab heave – but they will try to re-assign the blame. For your best chance of having your house fixed you MUST be prepared to eliminate conditions that could be considered to contribute to the problem.
If your home is outside the builder warranty period, it is your responsibility to fix slab heave. There’s plenty of information on this site on how to improve conditions around your house. If you need more help or a recommendation for an engineer please ask. I’ll try to find an experienced residential engineer that can help you.
The Claim Process
If you are within the builder’s warranty period, this is the claim and fixing process:
Monitor the damage. See my post about how to add some science to your monitoring and writing a ‘crack diary’. This will improve your chances of getting a good outcome.
Improve the drainage conditions around your house. This is your responsibility as a homeowner and you can not get out of this responsibility. Read this post and follow the recommendations in “Do this First”.
Make yourself aware of the insurance claim process for your state. Knowledge is your best weapon against slab heave.
Make a written complaint to the builder outlining the damage, when it occurred and that you want the builder to fix it. Do not mention legal action. At this stage you want to work with the builder – not against the builder. Your complaint MUST be in writing and you MUST keep a copy as evidence. Send it by email and request a read receipt; or send it by registered post; or send it by facsimile. Include a history of the damage (including photos you took and a copy of your crack diary).
Allow the builder fair access your property to assess the damage. A clever builder will engage a residential structural engineer almost immediately. Have your crack diary available for inspection or for copying but do not give your crack diary away.
The builder should, but doesn’t have to, give you a copy of the engineer’s report. If any aspect of the engineer’s report is unclear, ask the builder if you can speak to the engineer directly. If you disagree with any aspect of the engineer’s report, consider getting an independent interpretation of the report, or better still, an independent engineer’s inspection. Read here about what to ask any engineer that enters your property.
Follow the recommendations of the engineer’s report to the letter.
Allow the builder access to the property to make any repairs required in accordance with the engineer’s report.
Continue to monitor the cracks and keep your crack diary up to date.
Warning 1: Fixing slab heave is a slow process. You will not see improvements in crack width or floor slope occur very quickly. It takes a long time for heavy clay soils covered by a building to stabilise.
Warning 2: Bumping this problem up to litigation will slow the resolution process down infinitely. Most builders take the hands-off approach when lawyers get involved.
Warning 3: If you haven’t built your house yet – and your builder is using a waffle slab, carefully read and implement the builder’s and engineer’s advice on foundation maintenance (management of soil moisture around and under your house).
Have you just noticed some cracks in your house? I’ll bet you’re worried. Why did they appear? How do you fix the cracks?
First thing you should know: You’re probably going to need help to fix cracks in your house. They’re not normally the sort of house damage you can fix yourself unless you:
diagnose the problem
solve the problem
and can repair the damage.
So don’t be afraid to schedule an inspection of cracks or damage with a structural engineer. An engineer experienced in diagnosing and fixing the damage in buildings can offer invaluable advice and get you on the road towards satisfactory building performance.
Take Immediate Action
If you think your building is unstable – stay clear of the area and arrange for a qualified and registered builder to stabilise the area straight away. Then arrange for an inspection by an experienced structural engineer to design and document a permanent solution.
Start a Crack Diary
Depending on the nature of the damage, I sometimes recommend monitoring the damage.
Be a little scientific about this process because it will help later. I suggest that a crack diary records:
where the cracks are; and
how long the cracks are; and
how wide the cracks are.
Write a new entry every couple of weeks or when you notice new damage. “No change” is as important as “some change”, so write it down!
Here is the link to our handy crack monitoring kit that might help you keep track of the cracks in your house.
Digital photos are time-stamped so your photos and the diary should correspond if possible.
This is an excellent example of a monitoring photo. It clearly shows the crack and a piece of photocopied ruler has been bluetacked to the wall to help monitor the width of the crack.
Use a Water Level
You won’t be able to tell whether your slab is level just by walking on it. I use a professional digital water level. They’re expensive but make life easier if you do a lot of testing. Here’s a video I made about the water level I use:
You can make your own using material from around the house. See how to make your own water level. Rolling a marble on the floor will tell you a little bit but it won’t work on carpet. That’s why a water level is better.
Turn the Levels into a Contour Plan
Contour plans help structural engineers diagnose the cause of movement and damage in a house. The process is quite complicated so you will need an engineer for this part.
Ask for Help
Get the damage checked out by a structural engineer. Do this BEFORE you decide to sell your house and BEFORE a building and pest inspection and if there are signs of collapse BEFORE any part if the structure starts to fail.
Why is My House Cracked?
I’m a structural engineer. When I take calls about cracks in houses, this is what I want to know and why:
How old is the house?
If the house is within the statutory warranty period, you might be covered by the builder’s insurance policy.
The age of the house also tells me a little bit about the type of construction to expect and puts into perspective the age of the damage.
A 10 year old house and a 10 year old crack that hasn’t changed in 10 years is a different scenario to a 3 year old house and a 1 year old crack that is developing rapidly.
Did the damage occur as the result of an insurable event?
If yes or maybe, refer the damage to your insurance company. See Lodge a Claim below. Don’t forget to stay clear of any unstable areas. Your insurance company may arrange a temporary ‘make safe’ visit by a builder.
What sort of house is it?
Is your house single storey? Is it double-storey? Is it on a concrete slab or is it on pole footings? Is it brick veneer or concrete block or is it timber frame? Is the roof tiles or metal sheet or something else? This tells me about the type of construction but also starts to give clues on what could be causing the damage.
Has something changed recently?
Cracks in houses rarely just happen.
Is there a new retaining wall near the house?
Has the building flooded recently (see Building Insurance below).
Has the structure been changed recently?
Have you planted or removed trees or shrubs recently?
I’m looking for clues as to the cause of the damage. A recent change might give me ideas on how to solve the problem.
Get your pipes tested!
If I can’t link the house damage to a recent change or an insurable event, I will suggest you get your house pipes checked by a qualified plumber.
Leaks in pipes can cause a lot of damage to houses.
Engage a plumber to check the integrity of your sewer, stormwater and water supply pipes.
Use a plumber with a drain camera if possible because a camera is a quick, easy way to identify the location of a leak. However, to be certain there are no ‘invisible’ breaks, ask the plumber to flood your pipes and check to see if the water level drops (also called hydrostatic testing).
Get any damage repaired immediately!
Schedule an Engineers Inspection
This is where a structural engineer comes to visit your house in person. This is my preferred process:
Tour of the House
Take me for a walk around the house. Show me where the damage first appeared and how it progressed. I’ll only need 10 minutes of your time, but where the damage started is critical in helping me identify the cause of the damage.
The Site Inspection
I take photos of the outside 4 elevations of the house first – before I forget. I use these photos to confirm the locations of crack photos later.
I start at the front left-hand corner of the house and work around the outside of the house in a clockwise direction. I record the location, width and nature of any damage I see. I take a photo of any ‘good’ size cracks for the report.
I record sources of uneven soil moisture around the outside of the house including poor drainage, dripping taps, gardens located against the building and hot water systems that discharge water against the footing.
I categorise all damage on the inside of the house by starting at the front left-hand side of the front door and working through the house room by room by keeping the wall on my left-hand side. I record the location and size of cracks, gaps in cornices and gaps under walls in a schedule cross-referenced to a floor plan with the defect location.
I use a digital water level to record the floor level in each room. Levels are taken in easily reproducible locations such as at doorways and beside windows. That way we can compare levels in the coming months to determine if the slab levels are getting better or getting worse.
The causes of house damage I see the most of are:
Slab heave – an uneven movement of the house foundations caused by changes in soil moisture conditions. This damage is often identified as diagonal cracks starting at doors and windows, doors and windows uneven in frames, gaps under internal walls, broken cornices.
Consolidation of soft soils – downward movement of the house slab and footings one to two years after the house was constructed. This damage is sometimes caused by soft or loose soil becoming more compact under the weight of a house. Sometimes this damage is related to poorly compacted backfill over council sewer pipes and other underground infrastructure.
Slope failure – instability caused by building too close to a slope without sufficient footing protection or footing depth.
Poor workmanship – not as common a fault, but sometimes the plasterboard hasn’t been properly nailed or back blocked. This damage is often characterised by seemingly unrelated straight cracks in plasterboard ceilings or walls which follow plasterboard joints.
The direction of the cracks helps me work out which part of your building is moving and which part isn’t. If the whole house was moving uniformly, you probably wouldn’t have any cracks!
I also ask if you have your crack diary. An inspection of a crack at a single point in time can only be used to deduce a limited amount of information. If you are paying for a structural engineer, you may as well get some bang for your buck.
Lots of information is required to solve the problem of cracks in houses. The more you can tell me about the history of the crack the better!
The Slab Heave Investigation
As part of my desktop investigation and assessment I like to analyse and assess as much of the following sources of information as possible:
Results of the plumbing test that you commissioned.
Original footing and slab plan.
Original soil test.
Independent new soil test to current standards with soil moisture contents at 500mm centres.
Previously recorded slab levels.
Photos of cracks from your crack diary.
Bureau of Meteorology rainfall reports at the time your house was built.
The Slab Heave Report
If the damage doesn’t indicate impending structural collapse and the cracks aren’t very wide and you have only just noticed them I might recommend more monitoring.
Otherwise, my report includes my assessment of the severity of the damage, my opinion on the cause of the damage, and my opinion on how to solve the problem.
Note that I use the term “opinion”. An inspection by an engineer can only tell so much. Much of the building is covered with cladding (the structure) and dirt (the footings). So I am using clues and EXPERIENCE to solve problems and provide solutions.
But I can’t see through walls. Can you?
I have inspected many houses and repaired lots of damage, and occasionally homeowners place a higher priority on beautiful gardens against the house, or extra green grass or a large tree than repairing damage in a house. That’s fine. The next owner of your property could still find the report useful!
Fixing Cracks in Your House
The most cost-effective solution to cracks in houses is to find the cause of the damage, remove the cause and watch the cracks close up by themselves. No expensive chemicals. No extra footings. Just some minor repairs when the building stops moving.
A Word of Caution
Regardless of the age of the building or the age of the crack, if you’re in a rush and you decide not to ‘solve the problem’ before fixing the damage please DO NOT repair any cracks in your house or allow your builder to repair any damage without first taking photos and recording the locations of the cracks.
If you haven’t solved the problem before patching the cracks new cracks WILL occur. When they do, and if you engage a structural engineer at this stage, they will want to see the original damage as well as the new damage.
A Note on Statutory insurance
Is your house still within the builder’s statutory warranty period? Even if the builder no longer builds or the company has collapsed this is relevant.
Statutory insurance can be used to solve the problems and repair the damage. If the age of the house is getting close to the warranty expiring, act BEFORE it expires.
Lodging an insurance claim with the statutory insurance provider gets you on their books before the expiration of the policy. In Queensland this is the Queensland Building and Construction Commission.
The QBCC has a strict procedure that you need to follow and normally it involves working with your original builder first where possible.
Keep the lines of communication open. Be honest and as friendly as possible. Nobody likes cracks in houses and it can be a very stressful time for homeowners. so try to limit the stress by working with the people that can help you wherever you can.
A Note on Building Insurance
If the house is outside the statutory warranty period, you still might be covered by your building insurance.
Is the damage linked to an ‘insurable event’? If you had a burst pipe or an accidental impact or flood water through your house then the repair of the damage might be covered.
Note that the CAUSE of the damage won’t be covered. You have to fix the burst pipe yourself.
Each insurance policy is different, so read your policy before you make a claim. Knowing your rights is the best way to ensure you receive a fair go when fixing cracks in your house.
If you are after some definitive advice on the thickness of the concrete for a residential driveway slab, or what driveway slab reinforcement to use and how far apart crack control joints should be then you have come to the right place.
We would love to design your driveway concrete for you. Please contact Cornell Engineers on 07 3102 2835.
If you have a cracked driveway slab, maybe we can help you. Call Matt Cornell for advice or to arrange an inspection.
Concrete Thickness for Commercial Driveways
Ask Cornell Engineers to design your commercial driveway . We’ll specify the concrete thickness, the strength of the concrete for your driveway.
Commercial concrete driveways are designed specifically for the weigth of the vehicles usig the driveway, the number of times a day a vehicle uses the driveway and the ground conditions under the driveway.
Contact Cornell Engineers for more information.
Concrete Driveway Repairs
Oh no. Your concrete driveway has cracks in it. Cracks in a concrete driveway aren’t necessarily a bad thing but if your concrete driveway is brand new and you have concerns, Cornell Engineers can check to ensure your concrete driveway was constructed correctly.