A mezzanine (referred to in French as an entresol), often referred to as a mezzanine floor or sometimes a balcony, is an intermediate floor within a building. They are most often a semi permanent structure used within a warehouse environment. Mezzanines are also used as a permanent structure typically found in a theatre or apartment and are often referred to as a ‘loft’ bedroom or balcony.
Typically a mezzanine floor does not extend over the entire footprint of the ground floor space of a building and they are often a secondary structure fitted after the original building has been constructed. They are installed to utilise the space available, particularly if head height is available between the ground floor and the ceiling above.
Mezzanine floors are used to provide additional floor space in ‘industrial buildings’. ‘Industrial buildings’ include all those facilities traditionally referred to as ‘workshops’, ‘factories’ and ‘warehouses’ built in industrial parks, business parks and retail parks. Industrial buildings are typically large warehouse structures with adjoining and/or internal smaller, single or multi-storey office accommodation.
With new developments, we now commonly find that developers create the warehouse structure without office or welfare facilities, therefore creating a ‘shell’, giving flexibility to the new owner/leaser of the building, to install whatever facilities they require.
With new working practices coming into play due to the Covid-19 pandemic mezzanine floors will be utilised more than ever. Companies will look to add additional floor space to their existing premises to offer more space for social distancing, or alternatively if a company is moving they may look at smaller warehouses and utilise the available head height available. This will reduce overhead including rents and rates.
MATERIALS USED TO CONSTUCT A MEZZANINE FLOOR
MAIN STEELS (PRIMARY BEAMS)
Often referred to as a main beam, section beam or the primary steels. These steels span mezzanine columns and together provide the primary support for the secondary purlins. The beams are manufactured from universal I beam & Column Sections. Holes are drilled in the beam for the connection of cleats and to connect the beam to the column. The thickness of the main beam is determined by the required load on the mezzanine floor and also the required span between columns.
Subject to impending loads down each column, we will either use hollow box section or universal columns. Columns come complete with base plates which spread the load into the slab below. Mezzanine columns are connected to the primary steels using a top plate. Typically for standard mezzanine floors the columns are 100x100mm box sections with a 300mm base plate. However for large mezzanines with bigger spans these column and base plate sizes can increase.
PURLINS (SECONDARY STEELS)
These provide fixing points for the floor decking. Purlin spans and centres vary along with their section size subject to imposed floor loads and point load requirements. Typical centres are 600 or 700mm however they can be reduced dependant on the use of the mezzanine floor. The thickness of the purlin depends on the use and weight requirements of the mezzanine floor as well as the bay sizes determined by the column layout.
Generally mezzanine floors are fitted with tongue and grove 38mm particle boards which are a floor grade chipboard. The boards are fixed to mezzanine purlins in a staggered pattern through the use of wood to steel tek screws. Sometimes the decking is over-boarded with materials such as chequer plate or hardboard plywood to provide further protection dependant on the floors use.
As mezzanine floors are free standing structures and typically are not fixed to the fabric of the building they have a requirement to be braced to ensure they are stable. This is achieved by the installation of either cross braces from column to column or dependant on the size of the floor a stub braced which is fastened half way up the column and bolted to the floor. Typically brazing can be positioned in areas that cause no issues for the end user and for mezzanine floors that are to be partitioned, the bracing can be Incorporated into the partition and you would not even realise it was there.