Browse Forums General Discussion 1 Jul 01, 2012 4:19 pm I have a two story house and there is one room - a rumpus room - at the back which is single story. There is a problem with a slab in this section; it appears to have tilted. Along the ceiling where the single story section meets the double story section, there is a crack (quite a wide one at this point!) and outside, there is a vertical expansion joint between the brickwork in the single and the double story sections. It has gone wide at the top (I could put my fingers into it), the base doesn't appear to have widened at all. It looks like the whole single story section, as a whole, is tilting away from the double story section. Like the slab under the single story has dropped at the outer end furthest away from the double story section. The brickwork itself is not cracked, just the expansion joint, and inside the only plaster cracking is along that ceiling point and the outer wall - not so noticeable because it is mostly beside a window So each section of house is retaining integrity and squareness (no door or window issues showing any lack of square issues and no movement of cornice anywhere else), they're just pulling away from each other. We did not build this house; we bought it about 18 months ago. I do have photos of the ceiling crack at the time which was hairline, it is now 3-5mm (I haven't climbed up to measure very recently). It is in a new estate in Pakenham, was built by a big project builder. The couple who built it had it as an investment property for 5 years so maintenance was minimal. I have contacted the builder who were quick to send a guy out to check on it and they are continuing to be helpful sounding although not excessively proactive. The assessment was that the soil under that section has dried out. There are two trees, probably planted very early on, that are likely contributors. The soil down that side was/is exceedingly dry - even when there is a bog on the other side of the yard, it's still pretty dry underfoot there. Checking the soil at that outer edge, it was very very powdery dry at the time (later summer) and even now, in wet winter, it isn't much more than damp. In summer, we also had some fairly good size cracks open up in the lawn at the back on that side and that was when the ceiling crack became much more visible, the spring-early/mid summer months. It hasn't shifted much if at all in at least 2-3 months since the weather got wetter. When checking the ceiling crack carefully, it appears to have been patched in the past. We did get a building inspection done before we purchased but while a hairline crack was noted on the report, nothing more was said on it. It seems plausible that they are right, that the cause is the drying out of the soil. Is there anything else that could have caused this? In either case, do people have suggestions about which direction to go in to find a fix? I'm mostly wanting it stable; the plaster can be patched again as required, but I think that the the degree to which the brick expansion joint has separated at the top is concerning; I'd be happier if it could be closed up at least part way. Due to changed circumstances, we are intending to sell again in a year or two and thus do need it to look better as well as be better. Land settled May '14. Building the PD Hoffman39: 5/11=site start, 13/11=slab pour, 26/11=frame complete, 10/12=roof on, 12/12=bricking started. Blog: http://jyndeira.net/blog/ Re: 7 year old house, slab movement, what sort of fix? 3Aug 27, 2012 9:18 pm In my opinion the following options are your best bet: 1 Get quotes from underpinning contractors (they will get their own engineer for building permit) but make sure they are registered and get their proposal in writing. 2 Get a quote from "Uretek". They can stabilise and raise sunken slabs with expanding resin injection, again get proposal in writing. 3 Then compare and evaluate Foremost Building Expert in Australia,assisting with building problems/disputes, building stage inspections,pre-contract review advice for peace of mind 200 blogs http://www.buildingexpert.net.au/blog Re: 7 year old house, slab movement, what sort of fix? 4Aug 30, 2012 4:23 pm JimmyL I would be ringing a reputable structural engineer ASAP and getting on top of it. Nothing anyone says on here (no offence) is going to fox the problem. People often don't get the advice they need on forums as comprehensive answers cannot always be given due to the need to mention proprietary products and services. For this very reason, l can only give a generalised overview on this thread. The problem here appears to be a result of subsoil subsidence caused by reduced subsoil moisture levels as already noted by the builder's representative that inspected the site. It must be noted that reduced subsoil moisture content caused by nearby trees is not the builder's responsibility and l suggest that the builder has in fact been pro active by having someone identify the likely cause at his time and expense. I have previously commented briefly on trees planted close to the house in the thread linked below. viewtopic.php?f=19&t=57207 Trees generate high matric suction in the immediate soils and the negative pressures exerted by the soil matrix induces water to flow by capillary action and adsorption from nearby wetter soils. The pressure (footprint) exerted by a standard single story, 20 sq brick home with a tile roof is approximately 20 kPa. Many homes built since the drought broke have suffered from slab heave and this is when the re-hydrolysed subsoil exerts upward hydraulic pressures that can be many hundreds of kPa. It does not take a lot of variance in subsoil moisture levels to cause sub surface expansion or contraction. What you need to do is arrange for a geotechnical engineer to do a site inspection. This person will drill holes and take soil moisture readings at varying depths. To re-hydrolyse the soil, vertical holes will be drilled and lined with agricultural pipe, the moisture levels monitored by the home owner via Neutron Moisture Metres (NMM) buried next to the house a half metre or more down and water slowly added to the holes if the moisture levels are low. I say slowly because adding too much water too quickly can cause further damage. There are a couple of steps that you could also consider doing but No. 1 is a must do. 1. Treat the area around the trees with a soil wetting agent and if the trees are growing in a grassed area, remove the grass and apply a good thick mulch (but not up to the trunk) and regularly water this area. You should also buy a rainwater tank and harvest several downpipes. The tank would then supply gravity fed drip hoses that are under the mulch and coil away from the trees. 2. A similar hose should also be placed about 1 metre away from the foundations to also re-hydrolyse the subsoil along its length. DO NOT place the hose next to the house as this will cause other problems. The dry soil in this area will also have to be treated with a soil wetting agent. As the trees are a constant, so is the problem but you should be able to manage it by taking the above steps. Results will not be seen for several months, the same also holds true for a professional geotechnical management plan. La Nina has officially ended and we are highly unlikely to have 3 La Nina's in succession. What type of trees are they and how far away from the house are they? 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. Re: 7 year old house, slab movement, what sort of fix? 7Dec 16, 2014 1:12 pm Just bringing this back up for an update. The tree that was pointed to was a wattle. We had it removed it about 18 months ago and waited. It took over a year but the slab has returned to level. The expansion join in the brickwork has returned to looking (by eye) equal width top-to-bottom, although I haven't measure it recently to check exactly. The cracked plaster has closed up but will still need patching. As a extra bonus, the upstairs bathroom (one of it's wall was above the crack line which had a rather bouncy floor is much less so now. As far as I'm aware, this is not a reactive clay site. We're in the outer east - Pakenham. There is some clay in the soil, but also rock and silt and so on. The backyard drainage has been distinctly better in the last year as well, although I hesitate to say why. As we're planning to sell in a few months, I admit to being disinclined to investigate further as the problems are, for the present, resolved. I will, however, pass on a warning to the new owner about planting problem trees close to the house. They can do with that what they will. ETA: The builder is Metricon. Land settled May '14. Building the PD Hoffman39: 5/11=site start, 13/11=slab pour, 26/11=frame complete, 10/12=roof on, 12/12=bricking started. Blog: http://jyndeira.net/blog/ Re: 7 year old house, slab movement, what sort of fix? 8Dec 16, 2014 11:22 pm Good to get a update dragonchild. As you say the soil in Pakenham isn't that reactive and usually hasn't got enough swell to lift a double storey back to it's original level but sounds like you done the right thing and were patient. Re: 7 year old house, slab movement, what sort of fix? 9Dec 29, 2014 8:12 am How close was the tree to the house? Re: 7 year old house, slab movement, what sort of fix? 10Dec 30, 2014 2:02 pm StGeorgeBuild How close was the tree to the house? About 2.5 meters distant, estimated to have been planted when the house was built so about 7 years old. After it was called the problem, I did research (it was a wattle) and found a number of reports of wattles causing similar issues. No proof it was at fault, except that the cracks have closed up again and we have not done anything else. As the issue had been there for some years (there was evidence of prior patching before we bought the house), there isn't much else I can point to as a factor. Land settled May '14. Building the PD Hoffman39: 5/11=site start, 13/11=slab pour, 26/11=frame complete, 10/12=roof on, 12/12=bricking started. Blog: http://jyndeira.net/blog/ Re: 7 year old house, slab movement, what sort of fix? 11Dec 30, 2014 3:39 pm dragonchild StGeorgeBuild How close was the tree to the house? About 2.5 meters distant, estimated to have been planted when the house was built so about 7 years old. The type of tree, its probable age and the distance from the house should have been mentioned in the opening post! The immediate answer then would have been to remove it plus some subsoil remedial advice. 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. Re: 7 year old house, slab movement, what sort of fix? 12Jan 05, 2015 7:23 pm SaveH2O JimmyL I would be ringing a reputable structural engineer ASAP and getting on top of it. Nothing anyone says on here (no offence) is going to fox the problem. There are a couple of steps that you could also consider doing but No. 1 is a must do. 1. Treat the area around the trees with a soil wetting agent and if the trees are growing in a grassed area, remove the grass and apply a good thick mulch (but not up to the trunk) and regularly water this area. You should also buy a rainwater tank and harvest several downpipes. The tank would then supply gravity fed drip hoses that are under the mulch and coil away from the trees. What would be the appropriate degree for the water moisture to be reached? it might be hard to reach the defined ideal statue. Re: 7 year old house, slab movement, what sort of fix? 13Feb 16, 2015 11:29 am SaveH2O The type of tree, its probable age and the distance from the house should have been mentioned in the opening post! *blush* It didn't occur to me at the time that the tree could be related to the issue. I know so much more now! Land settled May '14. Building the PD Hoffman39: 5/11=site start, 13/11=slab pour, 26/11=frame complete, 10/12=roof on, 12/12=bricking started. Blog: http://jyndeira.net/blog/ Re: 7 year old house, slab movement, what sort of fix? 14Feb 16, 2015 1:11 pm Sunpower What would be the appropriate degree for the water moisture to be reached? it might be hard to reach the defined ideal statue. Trees need fairly regular deep watering but if the tree is too close to the house, it will suck the surrounding soil dry by a process known as matric suction. I had assumed that the tree was further away and that watering the tree would lower the matric suction in that area as an interim measure to prevent the situation worsening. 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. Re: 7 year old house, slab movement, what sort of fix? 15Feb 16, 2015 1:36 pm dragonchild It didn't occur to me at the time that the tree could be related to the issue. It is a common issue but you are now on top of everything and that is great to hear. You might enjoy the photo below, it looks great but... Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. Are they stumps or screw piles ? How much fill is there, is the site a class "P" ? A "H2" site is not supposed to have stumps it is supposed to have grid beams according… 1 1348 House movement is always a potential problem and there is a cause. Yes you should have it inspected by a competent and experienced building consultant 2 1316 Your house roof does not show rusting other than some surface rust on the flashings. In my opinion you dont need to replace or paint the roof other than treat surface rust… 1 5994 |