I once saw an episode of a house-building TV programme include a statement from one enthusiastic self builder condemning cost professionals for stifling specifications on the grounds of expense.  In his view it would be better to save on their fees and spend the money on having exactly what you want and when you want it. It made great TV but needless to say he went massively over budget and the project took much longer to complete.

Keeping to budget and managing your cash flow is a discipline in its own right and, regardless of whether you do this yourself or seek external help, someone has got to do it.  It needs to start right after you have secured your detailed planning consent and well before any suppliers or builders have been appointed. This is stage four of our generic programme (June article) and provides you with an opportunity to reconcile firm costs with your initial budget in terms of the specification mix. We’ll look at procurement routes next month but for now we’ll examine the impact of material products and drawings.

Drawing content

Planning drawings are simply not good enough to secure accurate material and labour quotes. Yes, they reflect the house layout and geometric shape, but they don’t tell the reader all that they need to know. What your builders, suppliers, building control and warranty providers will need to have will include:

  • Fully dimensioned and notated ground, first and, if applicable, basement and attic floor plans
  • All four main elevations clearly identifying the building height, ground levels, site contours and the locations of the differing external materials to be used
  • A main section reflecting storey heights, ground floor composition, intermediate floor details, roof structure, external and internal wall details and the locations and types of insulation to be used.
  • A foundation plan with service entry locations and internal drainage (soil stack) positions and details of below DPC blockwork and ground floor composition
  • A site plan with overall access, material storage locations plus any site welfare, a drainage scheme for both foul and surface water plus the origins of all service supplies and their routes across the site to their meter locations
  • Roof structure, ground and intermediate floor plans

In addition to the above it is also helpful to organise for any special details to be completed where you want to be certain about the finished outcome, i.e. window installation details showing internal and external cill treatments, soffit, barge and fascia boards and their implications for roof ventilation, bathroom layouts with waste pipe access locations etc. and so the list goes on.

Building Control

Building Control require justification that the building will comply with all of the relevant approved documents (current regulations) and most designers will therefore have a set of standard notes which will be applied to their drawings.  Where these are produced it’s important that you, as client, understand what has been selected/written to ensure it matches your final specification requirements as sometimes these notes appear on drawings and quickly become outdated by the decisions you take.

Furthermore, the energy performance of your building is now calculated in terms of its overall CO2 emissions and that means a holistic evaluation of your total specification.  The notes on the drawings must therefore be clear about air tightness and insulation levels, primary and secondary heating, overall areas of glazing, ventilation and any renewable technologies.

Typical specification decisions

The number of material decisions which will have a bearing on your drawing details are significant and below are some of the more obvious ones to demonstrate the point:

  1. Your building system. This might be a traditional brick and block cavity wall, timber frame, insulated concrete formwork (ICF), structural insulated panels (SIPS) or any of the newer types of construction methods.  All could be used to satisfy your planning approved drawings but each one will have very different design and engineering details and consequently set the tone for the detailed drawing pack.
  2. Brick bonding and chimney features. Some houses just appear more attractive than others and very often this is due to subtle choices concerning the brickwork.  Unless specified, the default brick bond will be stretchers but there are many other options to choose from which can be much more interesting and more sympathetic with window cills, heads and gable verges.  It’s really worth taking the time to examine your options but, as they involve more labour, they will all add to your costs.  When it comes to the chimney, you should definitely have it detailed with the correct proportions (for effective operation) and with the features you want to see before securing your brickwork prices.
  3. Space heating. Underfloor heating, by definition, needs to be concealed and this might steer you towards a screeded floor finish which might begin to influence the floor structure design itself. And this could be a different treatment at first floor level relative to the ground floor.
  4. Attic insulation. It is sensible to fully insulate your attic space at the time of building as the marginal cost of doing so will render this space much more useful.  However, warm roofs, where some or all of the insulation is laid over the rafters, creates a different set of details for the roof covering and your ultimate soffit box design.
  5. Heat recovery systems are excellent installations for both their eco credentials and your ultimate comfort in a new airtight property.  But they are space hungry and require sizeable ducts to transfer air around the building which are best incorporated right at the outset rather than as a remedial fit late in the day.
  6. Floor finishes. Stone floors and ceramic tiles require different substrates to vinyl or carpet and come in different thicknesses.  It’s easy to manage keeping all of your thresholds level if the various different floor treatments have been specified early enough to do so.
  7. Kitchens, utilities and bathrooms. Having these properly thought through at an early stage will save potential disappointment after you move in when things just don’t seem to fit!

The written specification & schedule of works for tender

My advice is to summarise your final choices in one specification and schedule of works document.  This pulls together your drawing pack, your planning approval, any relevant survey details or other reports, and describes for all the individual tradesmen/contractors exactly what it is that you need priced.  Where you intend to supply materials or services can be made absolutely transparent and everyone being invited to contribute will, therefore, be totally clear about your project objectives. If this is sent in excel it is also much easier to start making comparisons between one tender return and another.

So, in summary, the process of selecting your materials and briefing your designers is not necessarily a quick one but it is vital to do this comprehensively if you want to mitigate risk.  Good drawings and clearly thought through specifications will enable you to obtain firm quotes with little being left to chance.  Obviously this may create some tough decisions where the specification has to be reigned back, but it is much better to do this before you have started building even if it means your designer has to make changes to the drawings two or three times.

But the one drawback is that knowing your costs before building and being able to manage your budget along the way is unlikely to get you on the telly!


This article was written by Tim Doherty, and originally published for Build It Magazine. Tim is the Director and Principal Surveyor at Dobanti Chartered Surveyors, a building surveyors based in Tunbridge Wells, Kent. Dobanti offers a wide range of property services including design and planning applications, tender development, appointment of contractorsproject management of builds and renovations, building surveys, and more. Get in touch for more information, or read more online now. Further articles and blog posts can be found here.