Browse Forums Building A New House 1 Aug 08, 2015 1:29 pm Hi All, I am building a 22sq single story house on recently developed vacant land in the Keysborough area of Melbourne . I have just received a contract from the builder which includes an item for an Engineer designed concrete waffle slab (Class P) of $10K. The contract includes a copy of the Soil Test report (Geotechnical Site Investigation) which classifies the site as ‘P’ due to the depth of filling encountered. Fill was encountered to a depth of 2000mm, 2200mm and 2100mm respectively in the 3 bore holes. The report states that “If certification is provided to confirm that the filling is compacted as per AS 3798 specifications to “controlled fill” standard as per AS 2870, then an engineer designed waffle footing system suitable for this site’s reactivity may be appropriate for an articulated brick veneer dwelling. The waffle footing system may bear directly onto the compacted filling and shall be designed to account for a differential settlement of the fill by an Engineer experienced with the design of ‘rigid’ waffle footings.” A couple of weeks after this Soil Test report was prepared, I supplied the builder with a copy of the document from the developer certifying that the fill was controlled in accordance with the standards. Elsewhere in the soil report it is stated that “For the encountered soil profile and normal seasonable moisture conditions, we estimate that the characteristic surface movements to be less than 20mm”. My interpretation of this is that the fill is classified as “S” (slightly reactive). The builder’s standard inclusion is an M class slab. The contract provides no details of regarding the slab design other than the $10K price. I have two questions : 1. Is it reasonable to charge an additional $10K for the slab because of the 2m of controlled fill ? 2. Is it usual to include no details of the slab in a contract other than the 10K price ? Your comments, thoughts would be greatly appreciated. Thanks. Re: Extra Slab Costs due to 2m of Controlled Fill 2Aug 09, 2015 11:15 am Haven't gone through it personally myself but I'm soon to be building and my block has same class soil and similar fall. 10k sounds reasonable based on what I've read and ive heard people be charged a lot more. Hope you get it sorted. Re: Extra Slab Costs due to 2m of Controlled Fill 3Aug 09, 2015 11:55 am Hi Belongabank Welcome to H1 You will need to investigate this further as details will need to be provided. Just curious why would you sign a contract without full engineering drawings/Certification? Designer,Engineer (Civil,Const & Envir),Builder,Concrete & Masonry Contract.Struct Repairs Re: Extra Slab Costs due to 2m of Controlled Fill 4Aug 09, 2015 12:53 pm Haven't gone through it personally myself but I'm soon to be building and my block has same class soil and similar fall. 10k sounds reasonable based on what I've read and ive heard people be charged a lot more. Hope you get it sorted. Re: Extra Slab Costs due to 2m of Controlled Fill 5Aug 09, 2015 12:58 pm Hi Phillip_J and StructuralBIMGuy, Thank you for your replies. The building contract was sent to me to look over. I haven't signed it yet. I have now asked them to provide a copy of the engineers design of the slab and a breakdown of the costs. Best Regards, Re: Extra Slab Costs due to 2m of Controlled Fill 6Aug 09, 2015 1:22 pm The M Class waffle pod slab is barely suitable in most of melbourne so it annoys me when volumes builders put this as an inclusion cause its almost always going to be s class and above. Re: Extra Slab Costs due to 2m of Controlled Fill 7Aug 09, 2015 1:30 pm Just because your fill might not be expected to experience much movement, doesn't make it "s" class. The site is full of fill, it's not the soil. That is why your site is classed "p". Creator of superduperonium, expert at expert things, nobel laureate, can hold my breath for 10 minutes. Re: Extra Slab Costs due to 2m of Controlled Fill 8Aug 09, 2015 1:32 pm bananajules The M Class waffle pod slab is barely suitable in most of melbourne so it annoys me when volumes builders put this as an inclusion cause its almost always going to be s class and above. S is less reactive than M. So technically you are right, but I don't think that's what you were trying to say... Creator of superduperonium, expert at expert things, nobel laureate, can hold my breath for 10 minutes. Re: Extra Slab Costs due to 2m of Controlled Fill 9Aug 09, 2015 1:34 pm Ponzu bananajules The M Class waffle pod slab is barely suitable in most of melbourne so it annoys me when volumes builders put this as an inclusion cause its almost always going to be s class and above. S is less reactive than M. So technically you are right, but I don't think that's what you were trying to say... I meant H class. My mistake. In my case is I got a h class at no extra costs Re: Extra Slab Costs due to 2m of Controlled Fill 10Aug 09, 2015 1:35 pm But on the topic on slabs i have heard of people getting the old school slab that ended up paying extra. Sorry not a slab expert but maybe they are refering to a that. Re: Extra Slab Costs due to 2m of Controlled Fill 11Aug 10, 2015 3:18 am I had my land classified as P class with movement between 40-70mm. I had a waffle slab with piers. Now the list of defects are growing as the time goes on. I personally would employ an expert to verify anything before signing. But that's what hindsight is all about Re: Extra Slab Costs due to 2m of Controlled Fill 12Aug 12, 2015 1:49 pm Structuralbimguy my floor design are in draftings now too. Once done well push out contracts for financing this month. Given lands title sept oct one wouldnt have access to site to conduct relevant site surveys to get known siteworks costs. How else would you approach this, apart from buying already titled land to enable site surveys and engineering contour surveyd etc to be done in time for fixed /known siteworks to be included in costs? Re: Extra Slab Costs due to 2m of Controlled Fill 13Aug 12, 2015 3:18 pm 10k sounds okay to me. We added 1m of UNcontrolled fill (no compaction ... Couldn't convince anyone to do it). This added 'P' for Problem - to our already nasty soil E-D extremely reactive clay withmovement up to 75mm. Not counting these preliminary earthworks and retaining, our slab cost $37k. For that we got a traditional raft slab with 1 metre drop edge beams and and piers an extra 1 metre deep in the spots where the fill was added. We also had a thicker slab, double mesh and higher tensile strength concrete (32mPa). Re: Extra Slab Costs due to 2m of Controlled Fill 14Aug 13, 2015 8:28 am TomCat 10k sounds okay to me. We added 1m of UNcontrolled fill (no compaction ... Couldn't convince anyone to do it). This added 'P' for Problem - to our already nasty soil E-D extremely reactive clay withmovement up to 75mm. Not counting these preliminary earthworks and retaining, our slab cost $37k. For that we got a traditional raft slab with 1 metre drop edge beams and and piers an extra 1 metre deep in the spots where the fill was added. We also had a thicker slab, double mesh and higher tensile strength concrete (32mPa). I would have found another site Creator of superduperonium, expert at expert things, nobel laureate, can hold my breath for 10 minutes. Re: Extra Slab Costs due to 2m of Controlled Fill 15Aug 13, 2015 9:58 am I think the trick is to be well informed when buying land. I certainly was not. I had access to the engineering plans for the land and knew there was deep fill on the block. What I didn't know was that even with controlled fill, if it is deeper than 0.8m then the site is automatically classified "P". Of course, I also didn't know that what the Structural engineer would decide was a suitable slab design for the block. In hindsight it was quite a gamble. My excuse is that there is quite high demand for vacant land in Keysborough and only limited supply. So, when a block became available I immediately put down a holding deposit. If you're in a flood zone, not only are you dealing with the importation of fill and laying it down in 150 lifts to achieve compaction, you're going to have to consider… 4 5552 2 4363 |