2-3 Storey Commercial Buildings


    (Reference is made to Cordell's Building Cost Guide under the chapter "Building Cost Indicators" which lists such group separately also)

In most of these buildings the Kneebone & Beretta Group has found that conventional reinforced concrete floor systems have proven to be the most economical structural matrix. The basic restraints of reinforced concrete slabs consist of limited spans for flat plates and limited floor dimensions without joints.   Research by VSL Prestressing indicates that flat plates with average spans around 7.0 metres are generally more economical in reinforced concrete.  In addition the Kneebone & Beretta Group has found that in the case of one or two floors only, builders prefer to remain with conventional type construction such as reinforced concrete.   To give some guidance to the designers of such buildings we can make the following suggestions for proposed floor systems.

Over carparking areas the column spacing should not exceed 3 carparking widths (assumed as 7.8 metres) and the width of a driveway (assumed as 7.0 metres plus the column width) if flat plate floors are proposed. The thickness of such floors depend on the proposed use. For another parking floor, retail or office floor these slabs should be at least 220mm thick with no drop panels or 200mm thick with 150mm additional thickness in the drop panels.

Example 1:  Noosa Shopping Centre

Where floors need to support brick walls slab thicknesses should be increased by about 10% to limit deflections.  See ground floor slab for Strathfield Arcade.  Note on this sample where spans exceed 7.8 metres slab bands as beams have been incorporated. It is also  noted that such slabs are particularly useful where steps for ramps or garden areas are required.  The columns lay-out must continue if another floor is to be supported. Where columns are not continuous a transfer slab or beams are required.

Example 2:  Strathfield Shopping Arcade

For general information about slab and drop panel thicknesses see graphics attachment A:

Attachment A: Multi-span Flat Slabs for shops or offices (No Brickwork Loads)

In any case, whenever a designer of a commercial building needs advice on the structural system for his building please contact Kneebone & Beretta Group on This email address is being protected from spambots. You need JavaScript enabled to view it. and an engineer will get back for your assistance.