Filling to excavations

The volume of fill given in the bill should be the volume of the void to be filled. Thus. whether the material used is to come from the excavation in the first instance or to be imported to the site. the estimator must be aware that the volume of material required is much greater, for it will require compaction after placing. For example, hard re fill decreases by 25 per cent of its original bulk after placing and compaction.

SMM7 gives two classifications of filling to excavations and filling to make up levels. Filling to excavations is generally more labour intensive or more difficult by machine since it involves back filling around the actual building works. Filling to make up levels is assumed to mean bulk full over more extensive areas either inside the building or in the open. where it would be possible to load in with a machine or by directly tipping a truck. The latter is obviously the cheapest solution. although not strictly speaking the best construction method since any fill should he laid down in layers and compacted before the next layer is superimposed.

SMM7 also gives two thickness classifications. up to 250 mm and more than 250 mm, thus recognizing the additional labour in spreading thinner layers over wide areas.