Browse Forums General Discussion Re: Pre-wetting the block before earthworks? Yes or no? 3Apr 11, 2014 1:58 am 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: Pre-wetting the block before earthworks? Yes or no? 7Apr 11, 2014 11:08 am StGeorgeBuild SaveH2O Where would the water come from? Either the sky or a sprinkler system Not sure if the text in my post above answers this question. I was thinking that it would be either supplied from a neighbouring property or trucked in...overlooking the obvious that water is already connected. It was a long day. You could be on Bay of Biscay and the worst time to build is at the end of a drought. The sub surface soil moisture content under the house would more than replicate drought conditions. During the drought, Adelaide suburbs had the highest % and worst instances of foundation subsidence and house cracking of all the capital cities. I have files from 6-7 years ago with the suburb by suburb statistics and the % of affected houses in different Adelaide suburbs. No doubt your recommendations were influenced by case studies from that period. The soil's matric conductivity will slowly disperse the water. If you do a search for "matric suction" on this forum, you will bring up a couple of threads where I posted about matric suction and the influence of trees on sub soil moisture content. From memory, I also described the method that geotechnical engineers use to rehydrate the sub soil moisture content and their use of Neutron Moisture Metres to facilitate distribution where most needed. 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: Pre-wetting the block before earthworks? Yes or no? 8Apr 11, 2014 12:04 pm Yeah we already have mains water connected I believe it is Bay of Biscay soil. So I'm still not sure if I should be querying the builder if pre-wetting is really needed? What would the impact be if I don't pre-wet the block? Re: Pre-wetting the block before earthworks? Yes or no? 9Apr 11, 2014 1:29 pm StGeorgeBuild What would the impact be if I don't pre-wet the block? If it's a mandatory requirement and the decision comes back to you, then I suppose that it could possibly give the builder a get out clause if you did have problems later on and you had ignored the engineer's report. I assume that the builder has not put his overriding recommendation in writing. Others would be better able to answer this question and the subject of the builder's liability if he also ignored the report. Also, how would you prove that the mandated requirement was followed apart from pre and post NMM tests? The report however does state: "4.3 As a general rule the pre-wetting exercise will be deemed to be effective if moisture has penetrated at least to a depth of 1 m below the surface. This can be checked by the provision of exploratory holes." You should be able to hire a NMM but who's responsibility is it to do the tests and would you need the services of a geotechnical engineer for verification? A lot was learned about building design as a result of the drought. Faced with choosing between an engineers recommendation and the stated mandatory requirement Vs a builder's opinion, I would choose the former. Just ask the engineer for case study references, they are certain to be the result of professional geotechnical studies and recommendations. 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: Pre-wetting the block before earthworks? Yes or no? 10Apr 12, 2014 12:22 am Yes you have to comply with what the engineer says otherwise they have a loop hole. But I still question the wisdom of watering for 10 days and then expecting the clay to magically rebound instantly and then stop conveniently for the build. Anyone who knows these types of clays will realize the clay is going to rebound for a long time and unpredictably. The engineer should take this into account and design footings to suit the situation and not try to change the situation to suit footings. Re: Pre-wetting the block before earthworks? Yes or no? 11Jun 05, 2014 8:53 pm Hi I am in similar situation with StGeorgeBuild - p class e-d and required to prewet with engineers inspections for the slab process. Slab will grillage raft and 900deep and 250,wide- 120 thick will sl92,mesh. In regards to the prewet and also another topic about slab heave. House will be hopefully demolished by end of the month. I was thinking to not commence building until winter is over as it 'may' wet the soil through natural means along with the 2 hour prewet for 2 weeks (unlessI am wrong) though I had been advised if we can leave the block (after demo) to go through a full season that will be ideal but will be costly with mortgage. Cheers boosta Re: Pre-wetting the block before earthworks? Yes or no? 12Jun 05, 2014 10:00 pm I would agree with leaving it for 12 months a full cycle of the seasons.If it was my block I would do a soil test after demo and ask for moisture samples to be taken then 12 months later second soil test with moisture samples and you will be able to see if it has rehydrated.Some people may think that is over kill be the soil is really bad with a abnormal moisture condition ,moisture samples are pretty cheap. We've had the offer of a short term tenant whilst waiting for CDC/DA home approval and demolition for our knock down rebuild. It would achieve a pretty low rent as it's… 0 13750 The fastest thing a builder will do is bank your cheque, those systems work perfectly with lightning speed, everything else is slow burn. Just the way it is. 1 8705 Just to makea point about this, an approach that some people have found sucessful in negotiating these rises down, Is to provide some workings to the builder, specifying… 4 81704 |