If the span of the slab is very long, then we go for cable suspension slab which is supported on cable such as London bridge, Howrah bridge etc. Generally in construction of houses for every 4m we provide a column wheras in cable suspension slab for every 500m we provide a column. This kind of slab is provided where length of span is more and difficulty in building columns. The slabs are tied with cables and these cables are joined to columns.