HOUSE EXTENSIONS WITH ACA
Do you need more space for your growing family? Perhaps your home is in need of a makeover? Well, Allan Corfield Architects can help. It’s easier and more cost effective than you may think to extend or convert your garage or attic into a more habitable space. Now might be just the right time to consider a house extension.
ACA have completed numerous house extensions, mainly in the Central belt of Scotland – from Fife to Perth & Kinross, and from Edinburgh to the Scottish Borders. With the Government’s Permitted Development rights, you may not need Full Planning Permission for a house extension – this route makes it less expensive and time-consuming than you may think!
Over the last 6 years ACA have tailored the required house extension service to help the average homeowner get the necessary approvals in place – as well as assistance in appointing a trusted local contractor.
When ACA provide a Fee Proposal for a house extension, we will split the required services up into logical stages. These have a fixed cost and an advised timescale. The RIBA suggest that an average fee for this type of project would equate to between 9-12% of the overall Construction Cost.



At ACA, we believe our clients should know all of the main facts and costs before committing to a project, so we work on a fixed cost rather than a percentage – that way our fee isn’t determined by how expensive your build is!

STAGE 1 – SURVEY & EXISTING DRAWINGS
- Complete a basic measured survey of your existing home
- Draw-up your existing home in our 3D drawing package
- Provide Plan, Section & Elevations of your current home and garden
Estimated time – 1 week to complete drawings

STAGE 2 – INITIAL DESIGNS
- Meet with you to prepare a Project Brief (completed at initial meeting)
- Complete a Project Programme, estimating how long the project should take
- Prepare 2 or 3 design options in our 3D drawing package
- Prepare our BIMx model, so you can walk around your home on your PC, TV or iPad
- Complete a final option for your approval
Estimated time – 2 weeks to complete drawings
STAGE 3 – PLANNING OR CERTIFICATE OF LAWFULNESS APPLICATION
- Add relevant Planning information to drawings
- Complete computer visualisations to aid planning application process
- Complete online planning application submission
- Deal with any planning queries during the process
Estimated time – 2 weeks to complete drawings

STAGE 4 – BUILDING WARRANT APPLICATION
- Obtain Structural Engineer quotes for the design service
- Upgrade Planning drawings and add relevant construction information to layouts
- Prepare basic construction details
- Prepare warrant specification
- Complete U-value calculations
- Liaise with Structural Engineer and add their design information onto the architectural drawings
- Obtain local builders’ estimates for the works
- Lodge the Building Warrant application via the online portal (4-6 week review period)
- Deal with any warrant queries
- Help appoint a trusted local builder for your project
Estimated time – 3/4 weeks to complete drawings

If required ACA can also assist with on-site supervision, and checking of the local contractor’s work. However, we would hope that the contractor chosen would not need any assistance during the house extension construction – due to the quality of the information provided and the suitability of the contractor.
STAGE 5 – ON SITE SUPERVISION
- Regular site visits to check on work and provide any assistance to the contractor
- Provide Completion Certificate visit and certification via the local Council
Estimated time – 1 visit per calendar month (dependant on requirements)

ADDITIONAL INFO
Pre-application Planning Enquiry
Structural Engineer Services
GENERIC FEE PROPOSAL –
To give you an indication of how the costs are made up on an average house extension project, we have based this example of a single storey sun room extension with internal alterations. Budget approx £40,000 ex VAT:
Stage 1: | Stage 1: Existing Drawings | £540 (ex VAT) or 15% of total fee |
Stage 2: | Initial Designs | £900 (ex VAT) or 25% of total fee |
Stage 3: | Planning Application | £720 (ex VAT) or 20% of total fee |
Stage 4: | Building Warrant | £1,260 (ex VAT) or 35% of total fee |
Stage 5: | On site Supervision | £150 per visit |
Total fee | Total fee £3,600 (ex VAT) |
Note – Application costs and other consultant fees are excluded and paid direct by client.