Where to get relevant information?
Detailed site surveys are key to the beginning of any project. There are many digital tools and professionals which can assist in building a very detailed picture of a site and its surrounding context. However, what you decide to choose can depend greatly on the type of project, site and output you require. In this article, we will explore some of the survey options and how to gain a better understanding of your site.
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ARCHITECTURAL MEASURED SURVEY
On small residential projects, most architects will complete their own site surveys of a property to produce plans, sections and elevations. This will involve taking pictures and measuring the building. For more information on this type survey, please see a previous post Measure Survey 101. Whilst measuring the plans and sections can be straight forward, measuring the elevation can be very tricky.
A way of measuring and then drawing the elevation can be to measure the ground floor windows, cills and general building façade as well as a few bricks on site. Then from the elevation photographs, the brickwork can be counted and drawn up along with the previous information. It is always worth bearing in mind that the brick coursing or pattern may vary and that this should be taken into account when producing elevations. If the house does not have a visible bricks elevation, you can use the local council’s planning application viewing tool to see other examples of similar buildings on the street and their elevations.
For architectural detailing which is hard to measure both at height or not, many people try and take a picture as face on as possible. It can be further flattened on programmes such as Photoshop and then imported into your chosen CAD software. Here, you can then scale the image to fit into the size required and trace over.
For complicated sites, where further context is required, for listed buildings or to gain more accuracy and save time, a laser survey may be the prefect option. A survey company will use the OS information described at the beginning as a starting point. With a laser scanner on a tripod, they can create more detailed plans, sections and elevations through using triangulation from the survey station base point. These surveys will usually show heights of window cills and opening but may not show further details such as the window design, mullion, brickwork or detailed architectural features. These will usually be added in afterward by the architect.
Many companies can now also offer drone survey’s. This may be required if the roof is not easily accessible or if the site access is restricted by neighbouring buildings.
OTHER SITE SURVEYS & CONTEXTUAL INFORMATION
Once you have a contextual survey of your site and necessary surround area, these can be used by other people to build an even more accurate picture of the site. Every site is different and may require a long list of surveys to gain the best understanding of the area prior to planning, design, demolition or construction.
Some of these surveys include:
Drainage survey – There are a number of ways of conducting this survey depending on the project requirements. For small residential projects a CCTV camera and dyes will be used to see the condition and direction of existing drains. This along with site measurements of inspection chamber location and depth, combined with public drain information can help to build a better picture of drain location and depth. This information is necessary if an existing inspection chamber needs moving and extending or if new drains are being added to an existing system.
More detailed surveys use a type of sonar to work out the exact locations existing ductwork so pipes like gas mains are not damaged during demolition or ground works.
Habitat survey – These will need to be conducted be a suitably qualified professional if it is deemed that there is wildlife in the surrounding area that may be affected by construction work. Your planning office will normally detail the requirements. If your existing building is abandoned, a bat and bird survey may be required as they may have nested within the empty building. If you building is located within the countryside, other animals such as badgers may need to be considered.
Ecological survey – Usually called a tree survey, this may be required if there are existing trees near or on your site. A suitably qualified surveyor with use an OS map, National Tree Map data and a site visit to detail each tree on site, its height, canopy area, trunk location and thickness, root protection areas, health of the tree, etc. to produce a report.
Soil / contamination survey – This may also be a survey required by the local authority. There are a number of levels of information depending on the site requirements. First a desktop survey is carried out to ascertain any historical contamination. If this is deemed to be the case, one of several trial holes will be dug to take soil samples. There are then tested in a laboratory. If contaminants are found, further holes may be needed or a soil remediation plan may be needed prior to commencement on site. Foundation and ground floor design may also be affected greatly by the findings of these surveys.
Flood Risk – With the increased of Global Warming and more extreme weather events, flood risk can be a key factor in deciding whether to build on a site or how to build if there is a risk. This information is free to access via the gov.uk website. The map feature can show a number of different forms of flooding including surface water, risk from rivers or the sea and risk from reservoirs. If there is a high risk of flooding, a flood risk assessment may be required.
The Local Authorities Policies Map – Each council will have a policies map of an area. Looking at this can help give you a clearer picture of what the local authority is envisioning for the future of the area your site is in. This map will also usually contain any areas where architectural character is protected such as Conservation Areas or if there are any Article 4 Direction.
Listed Building – To check if a building is listed within England, you can use the Historic England website. If your site has a listed building on it, it may require a Listed Building Planning Application as well as possible extra reports.
Noise maps – If your site is near a busy road or railways, Extrium can be a useful tool in seeing how this will affect your project. If you are in an area with high exposure, you may choose to upgrade the sound absorption of your glazing or specify vents which are acoustically rated. If your site is near a London airport you may want to refer to the Airport Noise Mapping provided by gov.uk.
Ptal Map – Another London specific map is the WebCAT Ptal map, provided by Transport for London (TFL). This give a Ptal rating to your site which is a measure of distance from frequent public transport. It rates a point from 0 (worst) – 6b (best), 0 meaning there is very bad access to public transport and 6 meaning there are many public transport options. This map may help the designer and the council agree on parking requirements for a site.
If the site has very good connection to public transport you will usually be recommended against the provision of parking. If the rating is very low, you will have to provide parking according to the council’s requirements.
There can be many options when trying to build a better picture of your site. What you choose to do will depend on site specific constraints and budget. For example, a house survey for an extension will not require a point cloud survey. However, it is always helpful to know what the options available are, to best inform your client.
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Written by Aida Rodriguez-Vega, architect and researcher. Aida keeps busy by carrying out technical research and drawing new details for the ever-growing library and construction detailing books.