Browse Forums Building Standards; Getting It Right! 1 Sep 06, 2021 7:33 am Hi Braintrust Engineers! I am building in Marsden Park NSW and first-time poster here; I have read a couple of valuable pieces of feedback on this blog and this blog is really very useful to me. Site classification is P and Slab design (specified in the Soil report) is H1. Hs -1.8 m and Ys - 60 mm. 1. Soil Ys values from my soil test is 60mm and if you consider long term (30 years), there would be approx. few mm more settlement. So, if you add up both values then I am exceeding H1 Borderline limit (60 mm) and slab design should fall under H2 (61-75 mm) slab criteria. Please correct me if I am wrong. 2. I assume there would be more moisture content in winter so Ys winter would be higher than 60 mm. Am I right here? The structural engineer has designed the slab as H1, but I am not a structural engineer so not sure how to convince him to go with H2 slab. Do you think the above-mentioned reasons are sufficient or technically valid to persuade structural engineer? If you have other points, please advise. Builder contract says H1/H2 slab. Re: Soil surface movement Ys value - 60. H1 or H2 slab as p 2Sep 06, 2021 8:42 am are you an engineer? if not, you don't have much of a say. Imagine the conversation with the engineer " I was on this internet forum, and somone on there said blah blah blah". If you want them to over engineer it, you could ask for that. Though expect to pay more and no know if you truly got what you paid for. Dark matter scientist, can breathe underwater, mind reader and can freeze matter just by willing it. Trust me, its in my sig. Re: Soil surface movement Ys value - 60. H1 or H2 slab as p 3Dec 22, 2021 7:45 am I can't help you with the slab engineering but I suggest you have a look at 'a monitoring solution' if you're concerned (I don't think I'm allowed to self-promote in here so won't post any links).
I'm not a structural engineer but if your whole house H1 slab is moving up and down fairly evenly within those limits it's probably fine and as per engineering, the real issues come when just one area moves significantly in relation to the rest. The worst case is obviously one side heaving (up) and the other side subsiding (down) and in that scenario it doesn't take much to hit those engineered limits. Installing a few sensors around your foundations will help identify issues around your property BEFORE they become significant (or they can help diagnose and then monitor existing issues if retrospectively installed). The data is gold if you end up in any kind of conflict with your builder down the track due to major issues. Also note that there's a string of things you can do (and may be obligated to do under warranty conditions) to help prevent slabheave & subsidence issues. I strongly suggest you follow any and all of the guidelines provided by your builder. Common documents referenced by builder's warranty or covering the same recommendations: http://www.residentialreports.com.au/wp ... enance.pdf https://www.vba.vic.gov.au/__data/asset ... -sheet.pdf Re: Soil surface movement Ys value - 60. H1 or H2 slab as p 4Dec 23, 2021 2:31 pm Your Ys estimate is 40mm-60mm for the soil type in climate zone 2 but your classification is "P" so your engineer has to consider the extra effect of other factors related to your site eg trees, house removed, deep fill etc which create abnormal moisture conditions and excessive settlement or heave. The engineer should design your footings to cope with these extra factors and it probably won't be a standard "H1" type slab so it comes down to trusting your design engineer. The soil reports usually say eg(40-60mm) in normal soil moisture conditions but a "P" is saying the site may be subject to abnormal moisture conditions therefore the engineer has to allow for this in the design. Why was it a "P" site? Have look at your house plans and you will probably find that brick articulation joint has been missed. Maximum allowable spacing is 6M or 5.5M for a wall with window… 17 20993 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 7429 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 8910 |