St Albans · St Albans
House extension architects in St Albans
Rear, side-return and wrap-around extensions in St Albans (AL1), designed in 3D around how you live and around St Albans Council's planning expectations.
What do I need to know about extensions in St Albans?
Many single-storey rear extensions in St Albans can be built under permitted development (up to 3m deep for semis/terraces, 4m for detached, or 6m/8m with prior approval), but flats, conservation areas, Article 4 areas, side extensions over half the house width and two-storey schemes need planning permission from St Albans Council.
The rules at a glance
- Single-storey rear: 3m (attached) or 4m (detached) under permitted development
- Larger Home Extension prior approval: up to 6m / 8m
- Side extensions: single storey, no wider than half the original house
- Conservation areas and flats: planning permission usually required
General national guidance; every address is checked individually before design.
Planning in St Albans
St Albans District Council sets detailed guidance on materials, fenestration and boundary treatment.
Large parts of the district are Green Belt or conservation areas, which shape what extensions are acceptable. We design to the St Albans Local Plan and design guidance.
Typical housing we see in St Albans:
- Period terraces and semis around St Albans centre
- Post-war infill closer to the AL1 boundary
- Larger detached stock on the leafy northern edge
- Mixed-use frontages along the main high street
How we work
We start remotely: a Matterport scan gives an accurate 3D model of your home, we design options you review on video calls, then produce concept drawings. Planning and Building Regulations drawings follow only if your project needs them.
FAQs
Questions
Everything you need to know about working with DOR Architects.
Build costs depend on size, glazing and finishes. Most St Albans single-storey extensions we see fall broadly in the £2,500–£3,500 per m² range for build with a mid-range finish, excluding VAT, fees and the kitchen; see our North London extension cost guide for the full breakdown. Our Stages 0–2 (survey, existing drawings and concept design) are offered as a fixed estimated fee; planning drawings (Stage 3) and Building Regulations drawings (Stage 4) are optional add-ons only if you need them.
No architect can guarantee approval. We design to the St Albans Local Plan and design guidance and recent local decisions to give your scheme the best chance.
We start remotely: a Matterport scan produces an accurate 3D model of your home, so we can design and review options with you on video calls.