House Extensions

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.

House Extension - ACA

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!

Suggested Service –

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
Existing Drawing - House Extension ACA

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
Note – Full Planning Approval process will take a minimum of 8 weeks, Certificate of Lawfulness application (under permitted development) will take a minimum of 4 weeks.
Planning Drawing - House Extension - ACA

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
House Extension - ACA
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)
Timber Frame - House Extension - ACA

Additional Info –

Pre-application Planning Enquiry – If your project is contentious or doesn’t comply with Permitted Development it may be worthwhile getting pre-application planning advice. Some planning departments will discuss the proposals over the phone, but due to workload most of the Councils now require a formal application. A Pre-Application enquiry is a cost effective route which will give you a formal response from the planning team. The process usually takes 21 days and shouldn’t cost any more than £160.
Structural Engineer Services – You will need an Engineer on most house extension or conversion projects for the Building Warrant Stage. The engineer will access the existing home and ground condition, before designing the foundations and the super-structure for the house extension. They will also provide any calculations required in order to satisfy the building warrant application. A local Structural Engineer’s costs for a single storey house extension should be approx. £600 to £800 (ex VAT).

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: 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 £3,600 (ex VAT)
Note – Application costs and other consultant fees are excluded and paid direct by client.
Split roof - House Extension - ACA

Are you considering a house extension?

We would love to help you with your potential house extension - please get in touch to arrange a free initial consultation...