Provision of specialist surveying services through all phases of a construction project are core Mason skills.

Our involvement begins before ground works commence. A topographic survey along with underground services tracing, provide up to date information about the site. Ordnance Survey maps and aerial photography can also be provided by Masons to aid designers and architects during the initial planning stages.

From establishing a control grid, through structure monitoring to generating an as-built survey; Masons are there from start to finish.

Construction Services:

Surveying the site

Assessing the condition of the site is the first step in any design or conservation project. It is important to have suitable plans, to know the topography of the land, the structures present on the site and the conditions or land use on adjacent areas.

The main provision of such information is through a topographic survey conducted by a team of surveyors. Alternatively photogrammetry can be used to extract topographical information from aerial photography. Typically a survey captures building footprints, paving, roads, vegetation, services and levels.

Mason Land Surveys have more than 30 years experience of providing high quality topographic site surveys both from conventional survey and photogrammetry. Digital output can be layered into a customer’s schema of choice.

Underground service tracing (UST)

Tracing of underground services requires training and specialised equipment. Mason have performed UST on many projects, including extensive work at Heathrow Terminal 5.

Services need to be traced to provide a safe working environment for construction staff, to reduce disruption to the service networks and minimise cost. Once services have been traced their locations are surveyed and provided in CAD form to the customer.

The process often begins with a review of existing plans available for the site. A suitable strategy is then devised. Service providers for the various utilities are contacted to identify the locations of their services across the site for subsequent survey.

The survey team then enters the site to lift manholes and other service covers. Information about the pits beneath the covers can be measured, recorded and reported back to the customer. The pipes and cables within the pits then provide initial locational information for the services, which can be traced outwards. Other services will extrude through the ground, so again their positions can be surveyed and their routes traced.

To trace cables a variety of methods can be employed. C.A.T. and Genny (or similar) equipment can be used for underground service detection and clearance. To trace the routes of storm water or foul water drains, non-toxic dyes can be used. A sonde attached to the end of a cable and inserted into pipes is a method used to trace routes deeper under the ground.

Neighbouring structures – scan & photography

A photographic record of neighbouring structures is sometimes requested for gap sites as protection against claims. The position of neighbouring structures can also be surveyed. Mason Land Surveys have the ability to laser scan adjacent structures, so that their position and photo are recorded simultaneously.

Control grids and datums

Masons have provided local control grids on a number of projects. Once coordinates have been computed, a field survey team will place Permanent Ground Markers (PGMs) around the site. The brass studs used are punched to indicate the exact coordinate position to millimetre accuracy. On temporary or delicate surfaces other forms of marking position are used, such as adhesive targets and drawn marks.

Datums are surveyed and marked around the site before and throughout the construction process to assist contractors with structure positioning.

Setting out

As directed by the customer, Masons will set out to any level of accuracy requested. For structural steel work and other building materials this can be down to the order of millimetres, whilst for features such as paint lines it can be to centimetres. The surface to be set out over will dictate the type of marker used.

Monitoring

During the construction phase new structures can be monitored in a variety of ways. For large structures, such as the new Heathrow control tower, Mason have employed a positional monitoring network utilising automated total stations and GPS equipment. Surveyors can revisit a structure on a regular basis to check its position and alignment. A common task is checking the position of steel beams and their verticality.

Dimension checking

A valuable service provided by Mason to site managers as construction progresses. Dimension checking involves measuring the location and height of objects as they are built into the structure. Sometimes this can relate to structural features such as steelwork, so that clearances are maintained. Other times this service is performed within structures as services and other items are installed. Within today’s complex buildings ensuring that these items are in their correct position is critical. It is a time consuming and costly problem to fix if many fixtures once installed subsequently have to be moved.

As-built survey

During construction as-built surveys provide an up to date picture of the site to project managers, enabling designers and quantity surveyors to plan better. On completion of the project a complete as-built survey provides an invaluable data source for future development.

Notable projects