MyFirst
.....he put large wood chips all around the slab area except for areas with agi. drain and garage driveway area.
I am sure that the fill should be compacted, wood chips, mulch etc just doesn't cut it.
Browse Forums General Discussion Re: Slab Heave Cause? 81Aug 27, 2018 7:13 pm 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: Slab Heave Cause? 82Aug 28, 2018 6:33 am 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: Slab Heave Cause? 85Aug 29, 2018 6:29 am 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: Slab Heave Cause? 89Aug 29, 2018 3:42 pm MyFirst brokenstick My slab was poured on Friday (The removed the formwork in the afternoon) . On Monday evening I saw that they had added plastic and fill all the way around sloping away, and then covered with woodchips. I was pleasantly surprised to see this as other slab around me have just been left with big craters and puddles all around them. Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ Oh yeah, I didn't pay attention if mine they put plastic first before the wood chips... Is your slab waffle slab or raft slab? Waffle, on 36 piers and 16 screw piles Re: Slab Heave Cause? 90Oct 28, 2018 10:09 pm insider FirstHome builder25 I hope this helps you. This is just my opinion from the limited info you have posted and photos you have provided with my knowledge of your estate and the soil conditions there around the time of your house construction. Your soil profile is probably the worst scenario for slab heave.Higly reactive dry fill over highly reactive clay.The problem with this is that moisture gets trapped in the fill layer by the relatively less permeable undrlying natural highly reactive clay layer.This causes the fill layer to get saturated and swell fairly quickly even during construction.The natural layer below will get wet and swell also but at a slower rate. The loads put on the slab by materials used being light weight cladding and metal roof mean there is vitually no weight resistance to slab heave.The builder by overpouring the footings shown in the photos also has decrease the load on each perimeter beam footing. The builder has not complied with the standards by grading the ground away from the slab.The engineers drawings will include drainage recommendations and design because it is a highly reactive site.Going by the photos, the drainage design and recommendations are unlikley to have been followed.You should check the drawings. The builder by not having the downpipes attached i(seen in your photos) or temporary downpipes installed during construction again has not complied with AS2870 by allowing water to pond against the footing. The slab will not return to it’s original level as heaving up to 62mm bends the reo and cracks the slab on the underside.Once the reo is bend and stretched it will be permanetly be in a dish shape. I have seen slabs with less than 20-30mm return to close to their original level but not exactly.The soil will never return to the pre construction drought levels again there will always be some soil volume increase compared to the original pre construction drought dry moisture condtions. The good news is by putting a correctly constructed concrete path around the perimeter of your house you may have stopped the continued saturation of the highly reactive fill layer. Your limited test holes indicate that it maybe working as the soil is no longer saturated.If that is the case then you should monitor the slab floor levels for at least the next 12 months or so to see if the slab has stabilised.This should be your main aim if you want to stay there or not persue the builder. Will slab heave come back to you in the future?It is unlikely as now the swelling clay fill is in a drying phase if your borehole moisture description is correct.The first swelling phase of highly reactive fill is the largest so subsquent swelling (even if it does get that wet again)of this fill will be less. I have seen lots of slabs with gaps formed under the slab as the soil dries and shrinks down with the slab is permanetly bent up on the perimeter. The vast majority of your heave probably has come from the original dry conditons combined with the builders non compliance with the standards.There always many other factors but these two will be the most inportant. As SaveH20 has suggested you need a good Geotech to investigate.At the very least continue to do floor level surveys. Thank you Insider, I have setup talks with the builder as I have now also discovered the slab has not been built as per the engineering drawings. The notes stipulate that the slab must be founded 100mm into natural clay/virgin dirt however it is sitting about 200 mm above the virgin dirt. Re: Slab Heave Cause? 91Oct 29, 2018 7:26 pm Was wondering,as ive never seen it ,with clay been regulation around slabs to stop water soaking through,where does this clay come from and how pure does it have to be,as this reg seems to be treated as caspars reg by most builders Re: Slab Heave Cause? 92Oct 29, 2018 7:39 pm Joker Was wondering,as ive never seen it ,with clay been regulation around slabs to stop water soaking through,where does this clay come from and how pure does it have to be,as this reg seems to be treated as caspars reg by most builders Well compacted clay will be sufficiently impermeable to shed water away from the dwelling however clay that has dried out too much will shrink and crack. This may allow volume of water to get through before clay swells and closes up cracks 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: Slab Heave Cause? 93Oct 29, 2018 7:40 pm Joker Was wondering,as ive never seen it ,with clay been regulation around slabs to stop water soaking through,where does this clay come from and how pure does it have to be,as this reg seems to be treated as caspars reg by most builders joker Clay and silt from the site excavations or trench excavations and the important thing is it isn't compacted so water easily penetrates through and then the fill restricts evaporating so it is worse than doing nothing.Add a layer of tanbark or gravels for OH&S on top and then you have created a moisture accumulator and trap. Firstly the ableflex that has been installed needs (manufactures specification) a sealant cap over the top, preventing water draining down between the slab and the… 3 7774 1 6624 |