Let’s begin with a Measured Site Survey

Written by coreArchitect

Topics: Onsite adventures.

Who performs Measured Site Surveys? What are they? Why do we need them? Where and when are they needed? And, how are they done?

Having received some interesting comments to a recent twitter tweet on taking site photo’s I began thinking that maybe there’s a blog to be had on this subject somewhere. To be honest I’ve been umming and ahhing about attempting my first proper architectural blog; not being exactly sure where to begin.

A new building, design or construction project always starts with a measured site survey [apart from the small pre-requisite of meeting an interested Client and first agreeing a fee!], and I have therefore decided to start blogging on a topic that covers how a project starts: with a site visit and measured survey.

So, I’ve issued some meeting minutes via email, made a nice cup of tea, pushed that residential apartment scheme, that’s too tight to get all the services running properly to the side and here we go…

Who performs Measured Site Surveys?

That’s easy, Surveyor’s! Next question!

Actually that’s not quite true; yes surveyors, as their name suggests, do perform surveys, together with architects, interior designers, drawing office technicians, contractors and many others. A measured survey is one of many tasks performed by a surveyor see the Royal Institute of Chartered Surveyors [RICS] website for more details.

Measured information about a particular location is required where someone needs further details to complete a particular task, either: designing [architect/designer], working [decorator], installing [carpet fitter] or indeed selling [estate agent] and there are many others. To fully understand who performs a measured survey we really need to understand what one is.

So, what is a Measured Survey?

Measured survey, measured site survey and measured building survey are all one and the same.

There are many, many different surveys associated with and requested for Land and Building sites, the measured survey is as it says and consists of recorded measured dimensions. It is usually accompanied by some sort of photographic survey, where images act as a visual reminder to the person whom is taking the measurements; as not every dimension is accessible and some may simply be forgotten!

Measurements are taken that show the sites size: length, width, height and depth, they will also record sizes of other existing conditions that may directly affect any constructional work: other buildings, services positions [electric, gas, oil, telecoms, drainage, etc], large trees, rocks, rivers, and so on. It does not include specific details related to flora and fauna, nor ground conditions; further more specific surveys would be required to cover these topics.

Once recorded the measurements are then drawn-up electronically [usually] using a CAD drawing package; it’s a long time since I drew surveys on a drawing board, but it has been known. Electronic or hardcopy drawings are then issued to those needing the information: Client, Architect, Designer, Supplier, etc., to enable design development for any potential works or pricing of goods and services.

Strangely enough in most cases drawings very rarely show any dimensions or measurements on them! This is because if you are working on the CAD version sizes are in “real time” and if drawings are used they are drawn or plotted to scale and approximate measurements are taken from the paper.

It must be stressed here that this existing information is not produced in the same way as construction drawings where clearly figured dimensions would need to be shown.

Why do we need them?

Generally we need them to pinpoint and clarify information relating to volumes of work, services or products.

When purchasing property, or land, a buyer will instruct their solicitor to undertake the required legal documentation. The first survey carried out when purchasing land or property is usually a desktop survey. This type of survey is generally performed by Surveyors [another of their many skills] and covers information held by statutory registers. Such information provides notification of schools, public services, landfill sites, new road construction proposals, underground mining, major developments such as power stations, and so forth. All this happens prior to a measured survey and can even persuade a buyer to change their mind regarding a purchase; thus negating the need for any measuring!

Within the above documentation there will be a map of the property or land showing the curtilage of the sale as held with Land Registry. Such a map is usually based on, or is, an Ordnance Survey [OS] map, these maps have been produced by the national mapping agency Ordnance Survey; these are a form of measured survey only on a very large scale. See the Ordnance Survey website for more details.

A Client will often provide a copy of the OS map to a prospective architect so they have a better idea of the scale of the work, however, OS maps are usually at a very small scale 1:1250 or 1:2500, or smaller on a larger project. They are also quite basic and actually not especially accurate! At 1:1250, the Urban data capture standards tolerances are only to the nearest metre [3’3”].

When purchasing maps for Planning Applications it should be noted that license to copy only lasts for a year and copyright does not extend for reuse in the future; which can be costly, on the other hand, OS maps will soon be free online!

Clearly for the architect to create exacting detailed drawings from this, sometimes distorted, small scale OS map would not be a good idea. More accurate and comprehensive information is therefore required and so a measured survey is undertaken. We could all guess on the simple things but without precise sizes many problems can and do occur:

  • “No that house is not very close to the proposed extension!” – thus creating overshadowing
  • Yes a bed and a wardrobe will easily go into this room nicely” – only to find that yes they both fit in, but you can’t open the door!

Smaller less detailed measured surveys are required by carpet fitters, painters & decorators, etc, to accurately price for their products and services. Notwithstanding that accurately recorded projects already have this information available on the drawings we have already mentioned and further survey would not therefore be required, just issuing or copying of drawings.

The smallest measured survey, and perhaps less accurate [and some may say more exaggerated], is the estate agents survey where commonly just two dimensions are taken within a room, length by breadth, and often rounded upwards or taken to longest dimension. This is understandable as to describe a room 3836mm or 3.836m long by 2471mm or 2.471m wide is nonsense and it would thus be described as 4 x 2.5m; the same also applies in feet and inches. This is for comprehension and not for accuracy; I would say I was 6ft tall not 5ft 11 and ¾’s.

Where and when are they needed?

Projects vary in size and will differ in landscape, building type and also in budget.

An architect will have the skills to conduct a survey, and many do, however depending on the size and complexity of the survey required, dedicated Surveyors may be appointed specific to this task.

Usually, the measured survey is commissioned after a purchase in order to amass further detailed understanding of the site thus enabling a clearer vision for any [re]development. “Usually” commissioned first, but not always, because it can happen that a very large site will require an amount of feasibility work to be undertaken prior to any purchase and these tend to be done on the, not so accurate, OS Maps we discussed earlier and, at the risk of repeating myself, again this is for comprehension and not for accuracy.

A larger project Feasibility Study will give the Client a more accurate understanding in terms of the likely construction & project costs and attainable volumes. Should the costs or volumes not stack up in the Clients favour, and the scheme subsequently does not go ahead, there may be abortive consultant costs for the study; but not for any Surveyors fees as no measured survey was completed.

Surveys for smaller works are normally carried out by architects or architectural technicians. Architects deal with both new-build and existing buildings of which a large proportion of projects in the UK are extensions, refurbishment or restoration and all require some form of measured survey before any work is undertaken.

And, how are they done?

Survey information can be gathered from various free sources.

Great places are  Streetmap, Google Earth, Rightmove, etc, and, as already noted, from Ordnance Survey, however we know that measured surveys need to be more accurate than any of the above and to help produce accurate measurements a number of specialist instruments are used.

The arsenal can include a mixture of the following: measuring tapes [flexible] and rods [rigid], laser distance meters [Disto type] for quickness and longer dimensions and a dumpy level, yes dumpy level with tripod & staff for recording level changes and heights. Not forgetting Health & Safety hi-visibility vest or jacket, tough boots and hard hat. Other items handy to have are a jemmy [crow-bar] for opening up manholes & drains, a torch for those dark dank basements, a camera for photographic reference and a mobile phone if there is any sign of trouble. Ultimately if the site is empty, derelict or simply just unknown a survey should always be carried out by at least two people, just in case any accident occurs. The incidence of people falling down lift shafts or wells is fortunately rare but does happen.

Some of these instruments now record electronically and you can download your dimensions direct to a computer; otherwise a notepad and pen will be required. Different coloured pens are always better to use as they can denote different things, I myself sketch out spaces using a black pen, dimension the sketches with red and add additional notes with blue, this way similar lines can mean different things and when you are back in the office going through your notes the information is clearer to draw up.

External dimensions are straight forward and are taken with either long measuring tapes or laser sighting devices, internal with tapes, rods & lasers. Heights or spot levels are taken having first clarified a datum point, a fixed vertical point, all with the dumpy level.

It is often said that existing buildings are not exactly square! Using Cad equipment can make them so, but the reality of site is a different thing, older buildings are the worst with movement having occurred over the years. Simple trigonometry is therefore used; taking diagonal dimensions from corner to corner will automatically tell you how not square the spaces actually are.

Finally, the photographic survey as we have already noted is part and parcel of a measured survey as it will show all the detail that you cannot remember and will also show the information that may have been omitted. We are all guilty of making mistakes or forgetting to do something at some time and the photographs aim to limit those errors, let’s face it there is a lot of information that needs recording, and to visit site again and again would not be profitable.

The advice here is to take as many digital images as you can, from different angles, heights, etc, and upload them to a shared website Flickr or PhotoBucket for example. They are then a visual link to the site and always to hand as you never know when you, or some other member of the design team, may need to clarify something:

  • Which way did that door open?
  • Did that archway have corbels?
  • I’m sure this written dimension should read 1900mm not 1090mm!

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