September 2, 2025
When embarking on a home renovation, extension, or new-build project, one of the biggest decisions homeowners face is how to structure the work. Some people choose to hire an architect or designer separately to create plans and then bring in a builder under a different contract to carry out the construction. On the surface, this can appear logical: each professional focuses on their specialist role, and the homeowner retains control over the process.
However, separating design and construction into distinct contracts introduces significant risks. While it may provide a sense of independence, it can also create challenges with communication, accountability, costs, and timelines. Many disputes in residential building projects arise precisely because of this separation. Understanding these risks is essential before deciding whether to split responsibilities or adopt an integrated approach such as a design-and-build contract.
This article explores the main risks homeowners should be aware of when considering separate contracts for design and construction, and why integrated project delivery often reduces those risks.
When design and construction are separated, responsibility for mistakes or oversights can easily become blurred. For instance, if the builder encounters practical issues with the architect’s plans, each party may blame the other. The architect might argue the builder is misinterpreting the design, while the builder may insist the plans were unworkable from the start.
This lack of clear accountability often leaves the homeowner caught in the middle, attempting to resolve disputes between two parties under separate agreements. With no single point of responsibility, disputes can escalate, causing costly delays.
In a split-contract approach, design is typically completed before construction begins. While this provides detailed drawings, it often fails to account for real-world building costs. Builders quoting against plans they had no input in may highlight practical issues later, resulting in unexpected additional costs.
In contrast, integrated design-and-build models often allow the builder to contribute during the design stage, ensuring that what is drawn is also financially viable. Without that collaboration, homeowners may end up with a design that exceeds their budget or requires substantial alterations mid-project.
Smooth communication between designer, builder, and client is critical. When design and construction are contracted separately, the channels of communication can become fragmented. The architect and builder may not be accustomed to working together, leading to misaligned expectations and misunderstandings.
Even small communication gaps can result in errors, duplicated work, or conflicting instructions. This often places additional pressure on the homeowner, who may end up acting as the mediator between both parties.
When issues arise during construction, the builder must often seek clarification from the designer. If the architect is not immediately available, progress can stall. Similarly, if significant revisions are required to the plans, this can result in extended delays while new designs are drawn, approved, and costed.
With separate contracts, these delays are more common as there is no single team jointly responsible for overcoming challenges quickly. The result is a project timeline that stretches longer than initially expected.
Disagreements between designers and builders can lead to formal disputes. For example, if a structural issue arises because of a design flaw, the builder may refuse to take responsibility for correcting it without additional payment. The homeowner may then face the burden of pursuing the architect under a professional indemnity claim, which can be stressful, costly, and time-consuming.
When projects are structured under a single contract, the legal responsibility usually lies with the design-and-build company, providing the homeowner with clearer recourse if things go wrong.
Ultimately, splitting contracts places a heavier burden on the homeowner to coordinate the project. Instead of relying on one contractor to manage design, construction, and problem-solving, the homeowner becomes responsible for bridging the gap between two separate professionals.
This added responsibility can be particularly stressful for homeowners without construction expertise. What may have seemed like a way to retain control often results in greater complexity, more decision-making pressure, and increased risk of disputes.
Some homeowners believe splitting contracts gives them greater control and flexibility. They may want to use a specialist architect for design and then select a builder independently. Others believe this approach will save money by allowing competitive tendering once the design is finalised.
Not always. For very simple projects or where the homeowner has prior experience managing building works, separate contracts can sometimes work well. However, for complex projects such as basement conversions, extensions, or new builds, the risks of cost overruns, delays, and disputes are far higher.
In a design-and-build contract, one company is responsible for both the design and the construction. This ensures continuity, clearer accountability, and better collaboration. It also allows cost considerations to be factored in from the outset, reducing the risk of budget blowouts.
If flaws are identified, the builder may halt progress until the design is amended. This typically requires additional drawings and potentially planning resubmissions, both of which can cause costly delays. Responsibility for extra costs may be disputed between architect and builder, leaving the homeowner to manage the fallout.
Yes. Warranties on construction work usually apply only to the building phase. If issues later arise due to design flaws, the builder may not cover them under warranty, leaving the homeowner reliant on pursuing the architect instead. This can complicate claims and reduce protection for the homeowner.
If separate contracts are unavoidable, homeowners should:
Splitting design and construction into separate contracts may initially appear to offer greater choice and flexibility, but it introduces significant risks. From blurred accountability and cost overruns to communication breakdowns and legal disputes, homeowners often find themselves carrying the burden of managing complex relationships.
For many, a design-and-build approach offers a simpler and more secure route, with a single point of responsibility and smoother project delivery. While there may be exceptions where separate contracts work, homeowners should be aware of the potential pitfalls and take steps to mitigate them.
When planning a renovation, extension, or new build, it is crucial to weigh up not only the potential savings of splitting contracts but also the added risks. Careful consideration at the outset can mean the difference between a stressful, drawn-out project and a smooth, well-executed home transformation.
Ready to bring your home renovation or extension vision to life? At Milkov & Son Construction, we specialise in Architectural Design, Design & Building Process, Loft Extensions & Conversions, Extensions, House Refurbishments, and Interior Design. Whether it’s a single room makeover or a complete transformation, our expert team is here to guide you every step of the way. Contact us online or call +44 7951 625853 to start your project today.
