House Extensions.

Designed with care. Built with intent.

Extending your home, thoughtfully.

A well-designed extension does more than increase floor area — it reshapes how a home is experienced, improving light, flow and connection to its surroundings.

The most successful extensions feel inevitable, as though the house was always meant to grow this way. Achieving that requires measured design judgement, technical skill and a clear understanding of the existing building fabric.

125Architects designs house extensions across Scotland, from confident contemporary additions to carefully judged alterations within historic homes. Our work focuses on understanding the character and constraints of existing buildings, while also drawing on experience gained through new-build homes where projects begin from first principles. Whether working with a townhouse, rural property or listed building, our role is to help you understand what is possible — and to guide the project from first principles through to completion.

Designing extensions that belong.

Every building carries its own proportion, rhythm and material character. Good extensions are rarely defined by size alone. They are defined by how well they respond to the existing house — its proportions, materials and relationship to light and landscape. This approach is evident in our extension to a listed building, where contemporary interventions are carefully judged against historic fabric to create a coherent and confident whole.

We begin with close study of the existing house, allowing the design to emerge from what is already there. In some cases the addition is deliberately quiet; in others it is confidently contemporary. The right response is always specific to the place.

As RIAS Conservation Accredited architects, we are experienced in working with older properties where sensitivity and clear justification for change are essential.

A considered investment.

Clients typically approach us when they are ready to make a meaningful, long-term investment in their home.

While every project differs, architect-designed extensions typically begin from around £100,000 construction budget, with larger or more technically demanding projects often exceeding this.

Establishing an appropriate budget early allows the design to be both ambitious and grounded in reality.

A structured, professional process.

House extensions are frequently underestimated in their complexity. They demand the same level of professional skill as new buildings, often within tighter physical, practical and regulatory constraints.

Our service aligns with the RIBA Plan of Work and typically includes:

• feasibility and early design testing.
• planning strategy and applications.
• listed building consent.
• building warrant documentation.
• coordination with structural and specialist consultants.
• contractor procurement and tendering.
• contract administration during construction.

This structured approach allows projects to progress with confidence and reduce risk of costly decisions on site.

When extending is the right decision.

Moving is not always the better option. Many clients come to us recognising the latent potential within the homes they already value.

A carefully designed extension can:

• transform how natural light enters the house.
• strengthen connections to garden and landscape.
• create generous, flowing living spaces.
• support changing family life.
• enhance long-term property value.

These outcomes are rarely accidental — they are the result of careful thinking long before construction begins.

Contemporary additions and historic homes.

We are particularly skilled designing modern extensions working within sensitive heritage contexts.

Conservation is not treated as a constraint, but as a framework within which thoughtful contemporary architecture can emerge and flourish.

Early dialogue with planners and conservation officers can play an important role in helping projects move forward smoothly.

Experienced, architect-led guidance.

125Architects is a multi-award-winning practice led by a conservation-accredited architect, with a track record of delivering carefully considered homes.

We work closely with clients from first principles through to completion, bringing creative design, technical skill and calm professional advice to projects of lasting value.

Considering an extension?

The decision to extend is rarely only about space. More often, it reflects a commitment to staying — shaping a home around the life you want rather than searching elsewhere.

If you are considering a house extension, we would be pleased to discuss your plans, help you understand what is possible and assist in turning your ideas into reality.