Technology breaks spell of rights to light

Copyright: David Lawson 1996

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Farmers are celebrating the disappearance of a perennial annoyance    which  disrupted their lives for decades. No longer are they called away from vital work to chase intruders  spread-eagled in the exact centre of each field - always at the stroke of noon.   Meanwhile, building surveyors have stopped  picking grass from their hair while mumbling from candlelit books. Technology has  broken the spell of a mysterious order known only as the Rights of Light.

  This was not some  sub-Satanic sect, however. Much as apprentices were despatched on their first day at work to find a bucket of steam, fresh young surveyors found themselves handed a sketch, book and candle, and asked to measure shadows.  Actually,  most professionals remain convinced that rights of light involve some obscure incantation by technicians kept locked in back rooms. Yet it is a vital part of the development process which can cost millions if mishandled.

  For more than a century occupiers have had  the right not to be overshadowed by neighbouring buildings provided they have 'enjoyed' light for 20 years. But there are degrees of enjoyment. Parliament decreed in 1832 that a winter overcast sky at noon cast 500 'lumens' on someone lying in the middle of an open field - hence the gullible youngsters excursions to the countryside.

 Factored down to an individual room, it set a legal minimum of one lumen - or the ability to read by a single candle one foot away.  Calculating  shadows by more technical methods  prove little relief to the tyro surveyor, however. That involves setting up a grid at 850mm (desk height) above every floor of every room in a building next to a proposed development. Sight, or light,  lines then need to be laboriously drawn outwards.  Finally, each is translated via a Waldren Diagram - a swirling mass of curves resembling the map of every track running into  one of London's big rail stations.

  'It was a massive job,' says Elizabeth de Burgh Sidley, the RoL specialist with Drivers Jonas. And an intensely boring one, scream generations of surveyors. Every point might take 15 minutes to plot, and every room would have dozens of points. These would be drawn for existing light levels and every variation of a proposed neighbouring development. It could take weeks.  Today, DJ's technical wizard Derrol Euling juggles mouse and keyboard at his desktop computer and watches dots appear on the screen like stars at sunset. Each point shows the 0.2% level - the minimum legal right for the occupier. A room can be covered in minutes.

 Normally, he would flick on the machine  as he leaves each evening. Next morning, Ms Sidley has a series of new charts to help decide whether changes could help or hinder the proposed development. 'We drew up the program about three years ago and have been developing it ever since,' she says. 'It paid for itself almost immediately in time-saving.'

  There was some resistance to automation because specialists had developed an almost mystical aura in this area and some believed the process could not be improved. Now each firm has made the transition.  There is still no standard version, however, and the air of a secret brotherhood remains as each  follows slightly different lines.

  'I can't tell you how others work because everyone keeps their methods secret,' admitted  Ms Sidley. And a remarkable lack of movement by specialists between firms means few of these are revealed to the opposition. Each is similar enough to accept each other's data, however. In fact they have to be, as  there is regular interchange of information.

  That has fundamentally changed the way developers consider rights of light. At one time they would plough ahead regardless after getting  planning permission. Some still do.  'In fact, some architects are not even aware that rules exist for this area,' says Ms Sidley. That is understandable, as rights of light come under different laws. But it can be crucial to schemes, as  neighbours can  take out an injunction if they feel they are suffering. That can mean huge bills for delay - or even a permanent freeze on construction.

  In the past, these neighbours  would need to instruct specialists to work out light levels in their property and calculate the probable reduction. Then they would need to determine whether it was worth going to court.  The cost - and the prospect of  meeting all the costs of delaying a legal development - held many back. It was still a big risk for developers, however, particularly when liability lasts for six years after completion. Developers traded on ignorance - among professionals as well as occupiers. Big rewards during the boom also meant it was worth paying big compensation. Then there was the  expense of calculating the impact. An average site with 15 buildings around might cost œ12,000 to assess.

  'Now it is cheap and simple enough for them to do the calculations themselves  and give neighbours the information,' says Ms Sidley. This is where the similarity of systems comes in useful, as disks can be traded between specialists for each side. The technique Drivers Jonas adopted is to pull up a digitised map (courtesy of Ordnance Survey) and overlay the proposed development along with data contributed from a site survey. AutoCAD and an add-on called AEC produce 3D images of the buildings. The  firm's own program takes over after zooming in to to plot minimum light level lines according to weightings for the importance of each room affected.

  Developers can juggle with various layouts to gain the most advantage. 'Investors can look at this and determine the best returns they can expect within legal limits,' says Ms Sidley.  Massaging layouts are more common than injunctions nowadays. Neighbours also tend to seek pay-offs rather than  getting bogged down in costs and delays. 'We are currently negotiating with one developer adding floors to a building, asking for a share of the profits involved,' she says.

  There are a few holes left in the system, however. Lights blaze in Ms Sidley's little office, mainly because of a large blank wall nearby. Unfortunately, there is no compensation as this is part of the National Gallery extension  - an exempt Crown building. When it comes to light, some still have more rights than others.