The floor depth, or the structural depth, is a function of the clear span of the floor, the clear span between the supports; which might be steel beams, a wall, or column.
There are span tables for different types of construction methods, produced by the manufacturers. In a beam and block floor for example you can see from the manufacturer’s table that you’ll get 5m span from a 150mm (6 inch deep) structural floor. A plank floor (also called a hollow core floor) can normally span a little more so for the same structural floor depth of 150mm you can get a 7.5m span.
What tends to happen, particularly in care homes where rooms have a much wider open space, is that the depth of the required floor slabs to support the span are not taken into consideration early enough in the process.
In care homes where the rooms/flats themselves are larger than 7.5 meters, all the supporting walls are external with no columns or supporting walls breaking up the space. This is to allow free movement of beds, wheelchairs, and maybe a hoist as the needs of the residents change. To achieve this larger span, you would need 200mm or 250mm deep floor slab. The problems come when you have a three or four-storey care home and each floor needs an additional 2 or 3 inches than has been allowed for in the planning drawings, which increases the height of the ridge line, which has a planning implication.
It is important, even at the planning stage, that a care home with larger spanning floor plates gets some feasibility information on floor depth and floor construction. Quite often the floor depths themselves don’t make a difference it’s when an additional 150mm is needed for services, ducting and pipes is required, again on each floor, then the problem of ridge height rises occurs. It is quite easy to overlook this issue, especially if the planners are requesting the ridge height be brought down in the initial stages and the need for thicker floor slabs and allowance for services, ducts and pipes is not considered.
Another option instead of the thicker floor slabs is to add steel for support so the floors can be thinner but then you have to have a down stand beam on the ceiling which might ruin the clean lines of the architect’s design.
Planning for floor depths and the space for the services is important in the early stages of design and we can help with feasibility studies to ensure nothing is overlooked. If you have plans for a care home or any other multi-storey building where there are large floor spans, then give us a call and we can ensure that you have the support required. Give us a call on 01993 225085 or email mail@swjconsulting.co.uk for a no-obligation chat.
