Start with an organised information pack
Domestic clients must share relevant building information they hold, or could reasonably obtain, with designers and contractors. [3]
Provide the latest existing and proposed drawings, earlier structural reports and calculations, and records of completed work. Include concerns such as previous wall removal, cracking or repairs, even outside the room being altered.
Label each drawing by its date and purpose. Mark ideas that are still undecided rather than presenting several conflicting layouts as an agreed brief. For photographs, identify the room, elevation and direction of view. These are practical ways to reduce ambiguity, not replacements for a professional assessment.
What a survey can and cannot show
A structural inspection normally begins with what can be seen. Investigation may then involve lifting floorboards to inspect joists, opening a ceiling to check support, or exposing foundations locally. The engineer should explain what question each investigation is intended to answer. [1]
For example, a proposed loft floor may load a wall that appears continuous upstairs but sits over an earlier ground-floor opening. Planning Portal advises checking the supporting beam where new loft loads are added. Existing architectural plans alone may not establish that beam's capacity. [4]
Retrieving earlier records
Ask the previous designer, owner or builder for the relevant documents, and check what the council retains. Building-control records are not necessarily available in the same way as planning drawings. Camden, for example, requires the owner's written consent when another person requests access to plans and calculations. Other councils' access arrangements should be checked individually. [5]
Describe missing information honestly. “No drawing found” and “there is no foundation” are very different statements. Ask the engineer which uncertainties matter and which can be resolved without unnecessary disturbance.
Plan intrusive investigations safely
Let the engineer specify investigation locations and the information to record. A trial pit is an excavation beside a building, not a casual gardening job: undermining foundations and striking services are recognised hazards. HSE's underground-services guidance bases safe digging on planning, locating services and a safe excavation method. [6][7]
Where opening-up could disturb asbestos, arrange the appropriate assessment before disturbance. HSE distinguishes a routine management survey from the more intrusive survey used to identify materials affected by refurbishment. Ask the surveyor to match the investigation to the proposed area of work. [8]
Agree the next decision
Before booking investigations, ask who will provide access, carry out the work, inspect it and make good afterwards. Request a written record of findings and of any assumptions still unresolved. The aim is to supply the information needed for a defensible design, not to open every wall or dig around every footing without a reason.