Why you should avoid changes to the design once work is underway

OK, so you have all of your permissions, the builders are halfway through the job when you suddenly have a change of mind.  On the face of it, the changes you want aren’t that drastic. You simply want to move that wall forward by 500mm, or you have decided to add an extra window to the side, fine, you are the client, but those small changes could cost you dearly.


Changes to the design can easily fall foul of the original planning permission. Approvals usually require the work to be carried out strictly in accordance with the plans. Occasionally, minor amendments will be accepted by the planning authority on an exchange of letters and revised plans basis, but increasingly planners are insisting on a fresh application where they deem the changes material to the scheme.  Should a fresh application for your changes be necessary, this could prove costly in terms of time delays and uncertainty.


Unless at the tender stage you told the builder to; “name his price and the job was his”, it is likely that the builder priced the work competitively in a bid to secure the job. The competitive environment that kept the builder’s price reasonable would be reversed if you make changes to the work during the build. In this situation, the builder would be under no pressure to quote keenly for the changes, as he would be the only one pricing them. In fact the builder may try and recoup some of the profit he trimmed when he originally priced the job.


Changes to the design which are not sanctioned by the designer can move responsibility for future problems from the designer to the builder or the client. Here the greatest risk involves even small changes to the structural design, or details which could effect the performance of the building.

The design

Making changes during the course of a build can have a detrimental impact on the overall design. During the build, the owner is generally focussed on making decisions relating to details; such as the choice of cupboard fronts, the type of light fittings etc. This detail approach rarely allows for an overall appraisal of the scheme as a whole. Moving a window for example, may be motivated by a wish to make it central to a piece of furniture and an internal wall without regard to the effect on the external proportions.

The knock on effect

Many people don’t realise that changes often have repercussions to other parts of the build. For example a carpenter building the roof suggests that the roof would be stronger if a roof beam over a new staircase was installed below the ceiling line, as opposed to within the depth of the roof (a change fuelled by the carpenter wanting to make his life easier). The change results in the designed stairs not achieving sufficient headroom beneath the beam, which necessitates a change to the design of the stairs as well as alterations to the trimming around the stairs. This example which happened on a job I was involved with a couple of years ago, resulted in an increase in costs approaching £1000 for the more elaborate staircase and alterations to the bulkhead, whilst the clean lines of the open plan stairs were compromised.

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