Hi All,
I am building a 22sq single story house on recently developed vacant land in the Keysborough area of Melbourne
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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.