Browse Forums Building A New House 1 Sep 09, 2009 1:17 pm Recently found out that our slab has to be H-D class. Estimated site costs were around $13k but are now $23k. Site has a lot of large rocks in it and some slope and fill (yet to get specifics on these). What exactly is a H-D class? We haven't yet signed but are we able to get copies of the engineers report or soil test results or something? What do we need to ask for to get breakdown of it all? Is there a report we can ask for? Obvisouly we're not happy with the extra costs but if it means a better more stable foundation then I suppose at least that's something. Not really sure what to think of it. We do apparently get an M class included as per contract but that's standard but they recommend upgrade. Will H-D mean that everything will be stable and won't move? Is there anything to worry about in the life of the slab? Life is; then you tell yourself a story. Re: Soil Tests Back - Slab Confusion 2Sep 09, 2009 5:55 pm H class soil is the next step up from M. You'll be right, plenty of houses get built on H class soil, just means a bit of extra movement than a M but the builders will ensure all is OK (which is why it costs extra) This thread may interest viewtopic.php?f=31&t=9017 Re: Soil Tests Back - Slab Confusion 3Sep 10, 2009 10:39 am Thanks Louie. I just got the soil test report back and a breakdown from the builder and will add my details to that post. How can you know if you're being overcharged? Builders could easily make a lot of money by overcharging. How would you know otherwise? But like I said if it means things are more stable for the house, then I don't mind too much. And what is a Waffle slab? Life is; then you tell yourself a story. Re: Soil Tests Back - Slab Confusion 4Sep 10, 2009 12:02 pm H-D is similar to H, although there is deep-seated movement (deep moisture changes) where a standard H is shallow. How this translates to differences in footing design I cannot tell you. From my experience, the builder uses an engineering consultant to design the footing. The builder provides the costing based upon that design and advice, so you can be assured that what is built, will be what the house requires to be structurally sound. It is difficult to determine if the builder is overcharging. Independent evaluation is one way, or multiple quotes from different builders for similar sized houses is another. The question becomes what do you do if they are overcharging?!! Due to the nature of the fixed site cost arrangement, where the builder provides a sum (after soil testing), and then constructs, all of the risk is taken from you and placed on the builder. If there are conditions onsite that increase costs, the builder doesn’t come back to you for more $$$. However, the reverse is true where if things are better, they wont return any $$$ to you. (Rock removal can be an exception from reading other threads on here?). I think given that, it is fairly likely and quite reasonable that the site costs are inflated (to a point). Think of the pickle you would be in without this arrangement if half way through your site works, something came up and you needed to find another $10k+. Our site costs were quite high (not as high as yours) but I was comfortable with what we were paying for and slept well in the knowledge that nothing was going to come back and bite me hard on the … once we started. Look up some of the blogs on here for photos of waffle slabs. A picture tells 1000 words, but basically large foam blocks are placed to form a large grid. Concrete is poured around them and over to make your slab. Re: Soil Tests Back - Slab Confusion 5Sep 10, 2009 1:15 pm the different soil types affect the depth and number of footings. the more reactive soils, the more movement due to moisture content. basically, you need more and deeper footings the more reactive the soil is. waffle pods are not to save concrete - they create a grid whereby the concrete in the gaps form bearers to provide additional support to the slab - usually around 300mm deep. The theory is that the entire slab can adjust to small movements in the sub-surface soils without cracking. the price you have been quoted does seem high, but there isnt much you can do. the additional costs are due to a greater number and deeper footings which may need jackhamming/ripping of rock - and there will be additional material to dispose of. hiring excavators and dumping fees are pretty $$$ these days - you will be charged full price for the dumping fees, although it is likely that the builders will re-use the material somewhere else. at the end of the day, the slab will be fine. I have heard (cannot confirm) that the use of waffle pods is excessive for a lot of east coast soil structures. however it has become part of the building code of australia so it is now a nationwide standard. Re: Soil Tests Back - Slab Confusion 6Sep 10, 2009 1:53 pm Thanks SG and Sierra. That's helped a lot. Here are some of the details of the report. Site Classification: H-D Final Footing Design: Waffle Foundation System House Size: 21sq Location: Doreen Wall Construction: Brick veneer single storey. 2580mm external wall height. Cut and Fill Requirements: Up to 1800mm fall across excavation. Retaining Wall Requirements: ? Drainage Requirements: Provide silt pit for connection of agricultural drains to strom water drains. Provide agricultural drains to base of site cut. Upgrade stromwater to 100mm under future driveway concrete. Special Requirements: Provide concrete piering to slab (greater than 15 lineal metres) including additional concrete, mesh, labour and removal of excess soil. Provide additional slab mesh, provide rock removal, blasting and breaking and removal of rock from site. Provide silt protection to boundary of site where fall is in that direction. Compaction and proof roll as per soil report. Cost: $23000 What is this? Provide 1 riser pipe to front of garage for future connection to grated drain by owner after handover. ?? Life is; then you tell yourself a story. Re: Soil Tests Back - Slab Confusion 7Sep 10, 2009 2:05 pm Quote: What is this? Provide 1 riser pipe to front of garage for future connection to grated drain by owner after handover. ?? Is your garage level lower than the road ? THis would mean to run a strip drain in front of the garage when putting in your driveway to avoid water getting into your garage. The builder will provide a stormwater point for connection of the drain. Blog is now up - http://www.jbdave.blogspot.com/ Re: Soil Tests Back - Slab Confusion 9Sep 12, 2009 11:26 am oze Thanks SG and Sierra. That's helped a lot. Here are some of the details of the report. Site Classification: H-D Final Footing Design: Waffle Foundation System House Size: 21sq Location: Doreen Wall Construction: Brick veneer single storey. 2580mm external wall height. Cut and Fill Requirements: Up to 1800mm fall across excavation. Retaining Wall Requirements: ? Drainage Requirements: Provide silt pit for connection of agricultural drains to strom water drains. Provide agricultural drains to base of site cut. Upgrade stromwater to 100mm under future driveway concrete. Special Requirements: Provide concrete piering to slab (greater than 15 lineal metres) including additional concrete, mesh, labour and removal of excess soil. Provide additional slab mesh, provide rock removal, blasting and breaking and removal of rock from site. Provide silt protection to boundary of site where fall is in that direction. Compaction and proof roll as per soil report. Cost: $23000 What is this? Provide 1 riser pipe to front of garage for future connection to grated drain by owner after handover. ?? Hopefully this breakdown makes it nice and simple for you.. M Class Slab = 31.5cm thick concrete to your slab H Class Slab = 38.5 thick concerete to your slab HD Class Slab = 38.5 thick concete to your slab with further steel reinforcements built into your slab thus extra cost on top of the H Class Slab Your builder has put in an allowance to allow for rock removal which is totally resonable however the majority of the 23k would be the slab upgrade, and the piering to the slab. What this will mean is bored concete piers need to go quite deep into the ground to ensure your house does not move on the fill side of your 'cut and fill' due to the amount of soil being dumped on half of your block to get a flat building platform. Silt Pits, Agi Drains and Riser pipe will be required to be installed underground due to the cut side of your block now having a slope to stop any puddling or water build up against your slab or mortar on your bricks. Other items such as compaction and proof roll cost wise would be quite small. If you post the details of the Fill, A horizon, B horizon, C Horizon and What level your rock is at i will be able to tell you a little more. Re: Soil Tests Back - Slab Confusion 10Sep 14, 2009 9:27 am Thanks heaps wellinformed. Your posts are making it a lot easier to understand. I hope the following comes across right, i'm looking at the report and for the fill, A and B and will just post what's written. Horizontal Fill: M.C. (Dry) - clay, silt, brown, grey. Hole 1 (mm) 0-100. Hole 2 (mm) 0-200. Horizontal A: U.S (ML), MC (dry), Silt clayey brown grey, Hole 1 (mm) 100-200. Stiffened raft beams founded 100mm into the "A" horizon silt may be proportioned for an allowable bearing capacity of 50KPa. Horizontal B: U.S (CH), M.C (damp), Clay - silty, dark brown/dark grey brown to grey brown/grey, very stiff, refusal on hard basaltic holes 1 & 2. Hole 1 (mm) 200-900. Hole 2 (mm) 200-1800. Stiffened raft beams founded 100mm into the "B" horizon silty clay may be proportioned for an allowable bearing capacity of 150KPa. Piers founded 600mm into the "B" horizon silty clay may be proportioned for an allowance bearing capacity of 250KPa. Drainage: (written at top of page) is FAIR. Life is; then you tell yourself a story. Hi All, see above image. The required setback from the rear boundary in my case is 5m, as you can see the shape of the site and location of the boundary is slightly… 0 8451 My land is 260m2 (10m x 26m) located in claymore NSW. Under campbelltown council. I know in general the following setbacks would apply ground floor side setback =… 0 6908 Good luck with it. I don't know what the cost of a nice bidet seat with a 25mm air gap will be but you are obviously deducting the cost of a RPZ valve and its… 9 6983 |