Working space at between footing and excavation edge.

The measurement for working space in SMM7 is now given in square meters, provided that the face of the work requiring space is less than 600 mm from the face of the excavation.. There is no minimum depth below which working space is not measurable; if it is required it must be measured, At first sight this change in SM M7 might appear to be quite radical, but to the estimator it only rationalizes what he has always had to do: assess for himself exactly how much working space would be required. whether or not any was given in. the bill!.

All previous methods of measurement have treated working space as a theoretical allowance., where the distance from the surface worked upon to the face of the excavation was set in accordance with the depth of the particular class of excavation, Invariably all other factors, such as the nature of the soil. were ignored. Some methods of measurement did try to relate some of the difficulty factors to the measurement, but the allowance was still theoretical.

The problem then that the estimator faces is twofold. It is necessary to decide first how much space the workmen will need, and secondly how many external and internal corners there are on the plan! The first problem reviles answers to the following:

• To what depth will the work be carried out?
• What kind of work is involved?
• Is the working space partly or wholly below water level and, if partly, by how much? 
• Will the back filling be of any special materials? If so, then disposal of the excavated material will be require
• How much additional support will the excavations require? 

The second problem only occurs if the building is not rectangular in plan. If it is rectangular then there are always four corners to add to the working space excavation., no matter how many indents or cutouts there are.. Should the building plan be a polygon with more than four sides then careful note of the internal and external corners should be made, so that the extra excavation, disposal and support will be properly accounted for Having sorted these problems out, the estimator has to decide what width of excavation to allow, cube it up, price it. extend a total and divide by the bill quantity in square meters to arrive at a rate, But what about that width'? This is another case for the estimator's skill and or knowledge, backed up by meticulously kept records of car her work. Every job must he assessed on its merits.