Self-builders tend to picture design changes as a conversation with an architect. That may be the first step, but when inspiration strikes and you find yourself trying to rewrite approved blueprints, it is important to consider what happens next.
For example, moving a window six inches to the left once the frame is already in place is not simply a matter of repositioning the window. It could mean changing the header size above it, adjusting the stud spacing on either side, revisiting a load calculation that was signed off weeks earlier, and potentially reconsidering how the foundation supports the structure. In practice, a change made after groundworks or framing has started can involve several different trades, all of whom were scheduled around the drawings as they originally stood.
Why “small” changes rarely stay small
If a change to a wall, stair position, roof pitch, or beam span affects the structural engineer’s calculations, it may also affect the building control approval process. Where a change requires updated calculations or drawings after approval, the revised information may need to be submitted for review. The timing of that process depends on the nature of the change and the relevant building control service, so it is worth allowing additional time rather than assuming approval will happen immediately.
Materials can compound the problem. Structural steel, bespoke windows, certain roofing systems, precast retaining wall systems, and made-to-measure staircases are often ordered against a fixed specification. Some of these products can have lengthy lead times, particularly when they are manufactured specifically for an individual project.
Change the specification after an order has been placed and you may have to pay to modify a part-manufactured item, accept additional costs, or start a new production process. In some cases, this can put the original schedule under significant pressure.
Then there is the question of wastage. Does anything need to be completely replaced, or can part of the existing work still be used? Timber, fittings and other construction materials can be surprisingly expensive, so even relatively small amounts of rework can add unnecessary costs to a self-build project.
The trades don’t wait around for you to decide
Contractors work to carefully sequenced schedules. One trade finishes so that the next can begin, while subcontractors are often juggling several projects and arranging their work around dates agreed weeks or months in advance.
Push your electrician back three weeks because a wall has moved, and there is a real possibility that they will already have another project booked for that period. Finding another suitable slot could then affect the plasterer, decorator, flooring fitter and other trades further down the programme.
This is how a seemingly minor decision, such as changing the position of a socket or internal wall, can create a much larger scheduling problem. The delay is not necessarily caused by the work itself; it comes from the knock-on effect across the sequence of the build.
There is also paperwork trailing behind many changes. Depending on the project and the type of alteration, this could include a variation to the contractor’s scope, an updated quantity surveyor estimate, revised structural calculations, updated drawings, or an additional inspection. If the change affects an element that has already been approved or ordered, several people may need to review the new information before work can continue.
None of these steps necessarily happens instantly. Architects, engineers, contractors, suppliers and building control teams all have their own schedules, so a decision that takes minutes to make can sometimes take considerably longer to implement.
For self-builders, the safest approach is to treat late design changes as potential programme changes rather than isolated decisions. Before approving an alteration, ask which drawings, calculations, materials and trades could be affected. Confirm the cost and lead time with the relevant professionals, and make sure any necessary approvals are dealt with before work begins.
A little extra planning at this stage can help prevent a small change from becoming an expensive disruption later in the build.
