Which type of plan?

When quoting a fee for a measured building survey it is important for the surveyor and the client to be in agreement about the scope of the work. It usually helps if they meet on site to discuss the purpose of the survey, the level of detail required and the accuracy needed to ensure the final plan is adequate for the intended project.

The list below gives a fairly broad spectrum of the different types of drawings we can provide. For each type of plan the level of detail and accuracy will depend on its use.

Basic Detail

The simplest form of plan showing only the position of walls, doors and windows.

Suggested use: Lease plans, asset management, property portfolio.

Typical client: Estate Agent, Landlord, Solicitor.

Partial Detail

As for the basic plan but with floor levels, window, door and ceiling heights, overhead detail including beams, vaulted ceilings and sky lights. The example shown was for a licence application for a hotel where all fire points had to be shown and no levels were required’

Suggested use: Refurbishment, extensions, asset management of public buildings or commercial property.

Typical client: Architect, Local Authority, Property Developer.

Full Detail

As for the partially detailed plan but also includes the position of sanitary ware, radiators, kitchen units, shelving, cupboards, central heating boilers, water tanks, electric and gas intakes. Wall construction, RSJ positions, ventilation.

Suggested use: Refurbishment or asset management of listed buildings.

Typical client: Architect, Structural Engineer, English Heritage

We can also add any of the following items to the survey:

  • Room descriptions
  • Floor areas, GIA’s and GEA’s in accordance with RICS Code of Measuring Practice
  • Volume of rooms
  • Electrical sockets
  • Lighting, including switches
  • Water valves, stop cocks
  • Drainage pipes (external)
  • Internal drainage chambers
  • Fire safety features

Accuracy

Once the content of the plan has been determined it now remains to decide on the accuracy required for the finished product. There is no point in producing a highly accurate survey if the plan is merely intended to provide a Landlord with a record of floor areas for his property portfolio. On the other hand a basic plan with little or no level information would be no use to an Architect who needs to design a total refurbishment of a listed building.

In all cases the building will require a template on which the plans will be based. This can be a simple ‘taped’ template where some assumptions are made or a fully detailed instrument survey of both external and internal walls.

The method of measurement for each of the three main degrees of accuracy for a measured building survey are:

Un-connected

The external walls of the building are measured by tape and assumed to be at right angles to each other. If they are obviously not square to each other they will be calculated using diagonal checks. Window and door positions are also measured by tape and added to the plan. Walls are assumed to be vertical and the template is applied to all upper floors. The thickness of the external walls is measured and the internal walls are positioned using windows and doors as a starting point. Internal door positions and any other required detail are then added to complete the plan.

Accuracy +/- 50mm

Typical Use Although not particularly accurate this type of survey would be adequate for asset management where a Landlord or Estate Agent only needs to know the number of rooms and approximate floor area of a property.

Semi-connected

A ring of survey stations is traversed around the building and all external wall, window and door positions are measured using a total station. The traverse is continued through the building and the basic shape of all main corridors including door positions are surveyed with the total station. The thickness of the external walls are measured then the internal walls are positioned and any errors adjusted using the windows as a starting point and doors opening onto corridors as a check. Once the shell of the building is complete other detail such as sanitary ware, ceiling detail and heights are added. Finally levels are recorded in all doorways and at the top and bottom of stairs/steps using an engineer’s level. Checks are made on the verticality of external walls. If they are within +/- 15mm the upper floors are plotted using the ground floor template as a base. External windows on upper floors are measured using a reflectorless instrument.

Accuracy +/- 20mm

Typical Use This is the most common form of measured building survey being both economical and accurate enough for most projects. Can be used for larger asset management such as schools, public buildings and commercial property and is ideal for Architects involved in refurbishment design of large buildings.

Fully connected

External walls and windows are measured in the same way as for a semi-connected survey. But in this case all upper floors are given a unique template as with the ground floor. The traverse is extended throughout the building so that internal walls, doors and other major detail are positioned using the total station wherever possible. Linear measurements are checked and adjusted using a tape measure or disto. When all walls, windows and doors are positioned the remaining detail is added by taped dimensions. Finally levels are taken in all doorways and at the top and bottom of stairs/steps using either a precise level or a total station.

Accuracy +/- 10mm

Typical Use The use of a total station within the building and the linear checks required to achieve this accuracy make this type of survey time consuming and therefore expensive in comparison to the previous examples. Access to the building can also be a problem as it is obviously not wise to set a tripod up in the middle of a classroom full of children or in the aisle of a busy supermarket! Out of hours work is usually required here which can add to the expense. However if a listed building requires restoration or a structural engineer needs to know the precise position of load bearing walls and other structural detail it may be necessary to apply this type of survey.

3D laser scanning

GM Surveys do not currently provide this service. However it is a new and innovative branch of surveying that we are researching and we hope to be able to offer it in the near future.

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