Dear fellow Somersoft Forum members,
Our property had an extension added to it about 10 years ago and since early last year we noticed cracks on the extension's walls (not very big) and the floor sank below the main house. An inspector came and measured the inclined to be about 20mm, and told us this was likely due to soil movement that drew the extension's slab away from the main slab. The property is located in Melbourne west and is quite close to the beach. The site is classified H for "highly reactive clay sites".
I've spoken with three trades people and an architect trying to find a solution to this, but so far I'm only getting more confused... The advices I received from them were each quite different:
Our property had an extension added to it about 10 years ago and since early last year we noticed cracks on the extension's walls (not very big) and the floor sank below the main house. An inspector came and measured the inclined to be about 20mm, and told us this was likely due to soil movement that drew the extension's slab away from the main slab. The property is located in Melbourne west and is quite close to the beach. The site is classified H for "highly reactive clay sites".
I've spoken with three trades people and an architect trying to find a solution to this, but so far I'm only getting more confused... The advices I received from them were each quite different:
- A builder from a large corporate, said he must pull the extension down and rebuild it, and would likely cost $30,000-$50,000 (the extension is 8.5m X 2m, and only one storey).
- An architect, said he couldn't help me but suggested putting a levelling slab below the sunk part of the house, and think I can get the job done for $3000-5000. Note he has not been on site to inspect the damages.
- A private builder, said he wouldn't give me a quote for re-levelling the slab because he needed to see a structural engineer's report first. He did give me a quote for fixing the wall cracks and repainting, which was $4,000. He suggested I should get a structural engineer to inspect the damages first, which would likely cost $800.
- An underpinner, who has been doing underpinning work for 40 years (he's a bit old but I assume he has employees that do the actual work) came and inspected the house. He drew a plan of putting five concrete pours underneath the extension and use jacks to push up the extension from below. I asked him whether I needed to find a structural engineer, he said he has inhouse engineers to do the inspection and draw the plans but they all listen to him anyway so I don't need to hire someone external ? he did seem very knowledgeable so I don't think he said this to con me. He gave me a quote of $14,000 (GST and insurance inclusive).
- What's the best way to fix a problem like this? Rebuild, levelling slab or underpin? Is it considered a difficult/specialised job?
- Is it better to give the job to an underpinner or a builder? Because the underpinner wouldn't do anything other than the underpinning, once he finishes I will still need to find a builder/renovator to fix the walls, whereas the builder can fix everything and potentially charge me less in total.
- If I decide to go with the underpinner with inhouse engineer, shall I still get an independent structural engineer to check it out first? I know it's a good practice but it will cost money (~$800), and sometimes you get a bad engineer that can still mislead you (had this kind of experience before)
- Is the $14,000 quote given by the underpinner reasonable? What about the $4,000 quote for the builder's paint job?
- How would the underpin affect the property value in the future? Shall I try to sell it immediately after it was fixed or some time in the next 6.5 years while it is still covered under the insurance for the underpin work?
- If you have done similar works to your house please share your experience. Any recommendation of trustworthy underpinner/builder would also be highly appreciated!