Plans and who draws them
What are plans?
The primary method of showing a proposed new building or house extension is by means of what are generally referred to as plans. For a typical home extension this would include floor plans of any floor affected by the proposal. In the case of loft conversions this would generally include every floor in order to show the layout of any supporting structure below and also to verify that there is an adequate route out of the building (usually referred to as a means of escape) in case of a fire. The criteria for this becomes more onerous at second floor level and above (see Loft Conversions and Building Regulations). This would indicate the use of the rooms and positions of doors, windows and any fixed items such as stairs, sanitary ware etc. At the Town Planning stage this may be largely all but the Building Regulations and for construction purposes it will generally show other aspects such as the wall construction, direction of joist span and critical dimensions. There may sometimes be further details such as furniture layouts, electrical and radiator layouts and plans at other levels such as foundation and roof layouts although these will often not be essential for straightforward home extensions.
Elevations show in two dimensional form what the building looks like from each direction e.g. side, front, rear; with extensions the new part is generally shown together with the existing building for at least some, if not all the elevations. They can in some situations give a rather artificial view of the building looking at it in isolation to its surroundings, it also does not take account of perspective (i.e.things effectively diminish in size the further they are away) or from where one is looking, for example, a roof might seem more prominent from an elevation than it might effectively appear at street level. Occasionally three dimensional plans or models are produced or the elevations shown in a wider context with perhaps adjacent buildings, sometimes known as a street scene when viewed from the front.
In order to show the building in relation to its site, adjoining sites, roads and other landmarks plans need to show smaller scale block and location plans usually at scales of 1:500 and 1:1250 respectively. Location plans are often extracts from ordnance survey maps and may be purchased on separate A4 sheets from authorised suppliers.
Cross sections through the building (usually known as just ‘Section’) are sometimes required for Town Planning requirements but are more usually used to show the construction and its compliance with the Building Regulations. For a straightforward extension one section may be adequate but on more complex buildings two or more may be desirable to highlight different parts of it or taken at two positions at right angles to one another. There may also be larger scale sections highlighting particular parts of the construction.
Sometimes floor plans and elevations of the building prior to any alterations or extensions are shown either on the same plan or a separate one. Although not always essential it is a useful way for someone not familiar with the building to understand what is being proposed.
Plans should be generally drawn to a minimum scale of 1:100 although 1:50 or larger is generally preferred when showing aspects of the construction such as floor plans or sections.
Most extension plans will include specification notes showing the materials used in the construction such as sizes of joist, thickness of insulation etc. although the specification may form a separate document, (as would be the case in the example below).
Who draws plans?
There is no requirement that plans for house extensions need to be professionally drawn or where they are that the designer needs to be registered with any particular organisation. Particularly since the advent of relatively simple computer programs that produce plans more people have attempted to do their own particularly at the earlier stages, even if they know their limitations in dealing with the constructional aspects.
On relatively straightforward schemes this may be practical, on more complicated schemes a more experienced eye might improve or simplify a scheme. In addition although in practice simpler ‘Town Planning’ plans may initially be produced a detailed knowledge of construction and the building regulations will often avoid problems at a later stage which might involve changes to the original scheme or unduly complicated constructional details.
The term ‘architect’ is often thought of in relation to people who design a building but this title can only be used by people registered with the Architects Registration Board and generally members of the Royal Institute of British Architects (RIBA) . This is only obtained after considerable academic study and experience, however terms such as architectural consultant are not constrained in this way. There are many other professionals within allied fields of the building industry who may be competent at drawing extension plans such as architectural technologists, surveyors, building inspectors and structural engineers. Other professional organisation sites include www.rics.org, www.ciat.org.uk .There are also people who may have some skills at drawing from perhaps another industry who sometimes attempt drawing plans with varying degrees of success.
Who should you use?
In practice there is not a clear cut answer. If you are looking for a ‘cutting edge’ design it may generally be better to use an architect. A large practice may not give a modest extension the attention you may hope and some practices may be more comfortable dealing with more conventional schemes or commercial projects. The best way to select is through recommendation provided you are comparing similar types of schemes. Alternatively look around for recent extensions that you like and find out who designed them and ideally enquire how the customer/professional relationship progressed. Some professional organisations such as RIBA (for architects) can provide details of members in your area. Failing this, or if you are considering a fairly straightforward scheme names can be obtained from directories such as Yellow Pages or Thomsons under headings such as architectural services, building consultants, surveyors.
Some people will offer free initial visits which will give an opportunity to see if their initial ideas seem to coincide with yours as well as to obtain an idea of the fees. Clients sometimes ask to view copies of previous plans however; bear in mind that plans are only a means of communicating the proposals of a householder to the council, builders etc. A slightly untidy drawing might actually show a well thought out design, conversely a beautifully drawn scheme might be highly impractical.
Fees do vary considerably from the larger well known architects practice to the draughtsman doing a few extra jobs in the evenings. Clarify what is covered, for example it may be reasonable to charge extra for significant changes to a scheme but routine minor amendments for perhaps the building inspector may be rather less warranted. In addition there could be additional services such as structural calculations which they are possibly unable to provide themselves and they do not include in their prices. There are in addition other fees such as to the council which are nearly always charged on top of any professional fees.
Finally there is the extent of services required; it has largely been discussed in relation to just producing plans. There are other services that some practices will offer such as obtaining tenders for the works, and project managing. Obviously the fees for these services are a lot higher although if you don’t have the time or confidence in dealing with builders it may be worth investing in them.
At the design stage the most likely additional requirements after plans is structural calculations. For a conventionally constructed building designed within the criteria of the building regulation approved documents it is quite likely that they will not be required. However, if more specialist foundations such as piles or rafts are used or brickwork exceeds the normal limits then individual calculations will be required, also if less conventional forms of construction are used. Some fairly standard component such as roof trusses or precast floor beams may require calculations but these can generally be supplied by the manufacturer, their cost effectively being built into the overall price of the product. In addition some steelwork suppliers offer a design service.
Loft conversions which may at first sight seem straightforward will often require structural calculations. Although floor joists sizes can in theory be taken from standard tables, because in loft conversions they may often support the roof or dormers the loads for which they were designed do not strictly apply. Often they will end up a size larger than they would otherwise have been but will require individual calculations to confirm this. With the advent of fairly simple computer programs for components like steel beams and floor joists some architectural designers might offer this service themselves without necessarily resorting to a structural engineer, although probably only suited to fairly straightforward situations.
For a heavily glazed extension that significantly goes beyond the simple rules within the thermal regulations it is sometimes possible to justify with calculations. (see Building Regulations) In a simple case it may be possible to just increase the insulation for one component such as the walls but beyond this a more sophisticated energy calculation needs to be made including the existing building and comparing it with a theoretical extension that does comply. This really needs someone with the S.A.P. computer program to calculate and so will often not be something that the architectural designer can necessarily provide themselves.