A lot has been achieved by the time planning consent has been granted. A site/building survey has been undertaken, client briefing, sketch options and proposals, developing these, drawing up planning-ready drawings of a chosen scheme, preparing a planning application, including a supporting statement and going through the planning process that sometimes needs amendments to secure consent.
Once the design has been approved by the council (under Planning or Permitted Development rights) there are broadly two routes forward. With, or without detailed design.
Without detailed design.
Numerous successful schemes are built using planning drawings only. A number of TSA projects are successfully completed in this manner (project links 1, 2 and 3) and many builders are used to working this way and will use their experience, knowledge and team of sub-contractors to fulfil the design. Your relationship with your architect will essentially cease to exist (although they will always answer the phone!). Detailed design decisions will be down to you and your builder. The builder will arrange for building control approval and a structural engineer to be appointed. If it is known that this route is to be taken, a little more information (materials, sizes, key features etc) can be added to the planning drawings to assist.
Typical planning drawings:
With detailed design.
In this route, your architect will begin preparing detailed, in-depth drawings showing how the building should be built. They will include roof, wall, floor construction information, as well as detailed floor plans showing electrical layouts, kitchen layouts, materials etc. Internal room elevations can be drawn up for complicated rooms such as utilities and kitchens to get cupboard heights etc. It is at this stage that a structural engineer would be appointed to feed in structural information into the architects drawings. Building control will be consulted and the plans issued to them for ‘plans approval’. This more complete package of information can then be sent to builders to price, with most decisions detailed out before starting on site. It is more suitable for complex or precise projects and/or where a more thorough set of instructions for the builder is desired/needed. (Project links 1, 2 & 3)
On some projects it is beneficial for the architect to be appointed to continue as a Contract Administrator during the on-site stage. This can be quite time-consuming, and relies on a detailed schedule of works to be priced. (Listing out tasks with broken down prices for each) This enables the Contract Administrator to correctly approve builder’s invoices for work completed in accordance with the agreed contract information and overall price, as it progresses.
With or without this Contract Administrator service it is advisable to sign a building contract. They are available off the shelf, and protect both yourselves and the builder. The JCT, FMB and RIBA all produce domestic specific contracts) Emails and such can be considered binding contracts but an explicit contract based on legal precedent & experience is more thorough. Unfortunately some of the domestic contracts available are fairly silent on some matters (to remain lightweight and accessible in paperwork terms) and rely on both parties remaining reasonable. As with most things in life, it pays to remain amicable and understanding of both parties point-of-view throughout.
Detailed design takes a fair amount of time, but it does allow quotations to have like-for-like cost comparisons and confirms what you are going to get as an end result before things start on site. It is a stage that often requires a fair amount of research and consideration to ensure that details are suitable. Manufacturers and specialist suppliers are often consulted at this stage too for any unusual situations.
Pre-Construction Information relating to site-specific H&S risks is also documented to pass onto contractors who will not be familiar with the site or H&S implications of the design. (All construction is risky to H&S however some particular design choices will impact this differently. For example, very heavy rooflights or building near unstable garden walls, unavoidable use of vibrating/impact tools etc)
Typical detailed design drawings:
Ultimately the decision is up to you, there are pros and cons to both approaches. Detailed design costs time and money, but could save you both in the future during construction. On the otherhand, if the construction is straightforward, then decent builders will know how to construct and can work well with you on site. Your architect will help guide you through and make the right choice. TSA projects tend to fall evenly either way, with the smaller or more simple projects building from planning drawings alone.