Last reviewed: June 2026
TL;DR- Custom build allows buyers to commission a home built to their specification by a developer or specialist contractor, rather than building it themselves.
- The distinction between self build and custom build affects eligibility for certain government schemes and planning policies, but both use specialist stage-release mortgage products.
- The Help to Build equity loan (check GOV.UK for current availability) supports both self and custom build with smaller deposits.
- Custom build plots are increasingly available through local authority custom build registers and specialist developers.
Self Build vs Custom Build
The terms self build and custom build are used interchangeably in everyday language but have a specific distinction in planning and housing policy. Self build typically refers to a project where the individual is directly involved in the construction process - either building themselves or project-managing contractors to build a one-off home. Custom build refers to a model where a developer or specialist contractor builds the home to the buyer's specification within a defined framework - the buyer designs and customises but does not project-manage the build.
The Self-build and Custom Housebuilding Act 2015 (as amended by the Housing and Planning Act 2016) requires local authorities to maintain registers of individuals seeking self build or custom build plots and to grant sufficient planning permissions on suitable land to meet the demand registered. This has increased the supply of serviced plots for custom build development in some areas.
Finance for Custom Build
Custom build projects are financed in a similar way to self build: a specialist mortgage releases funds in stages as construction progresses. Because a developer or contractor manages the build process, the fund release schedule is typically tied to the developer's payment schedule rather than the borrower managing individual contractor payments. This can make advance-release mortgages more appropriate, as the developer requires payment at defined milestones rather than after work is completed.
Some custom build developers offer their own finance arrangements or have preferred lender relationships to simplify the process. These should be compared with the wider market before committing - a preferred lender arrangement may not offer the most competitive rate for all buyers.
Help to Build Equity Loan
The Help to Build equity loan scheme, when available, provides a government equity loan of 5-20% of the estimated cost of a self or custom build, enabling buyers to proceed with a smaller deposit on the main mortgage. The equity loan works similarly to the Help to Buy equity loan: interest-free for an initial period, with interest charged thereafter, and repayable when the property is sold or the loan is redeemed. The current availability, eligibility and terms of Help to Build should be confirmed via GOV.UK, as the scheme's status may have changed.
Finding a Custom Build Plot
Custom build plots are available through: local authority self build registers and related planning permissions; specialist custom build developers who acquire land, install infrastructure and sell serviced plots; community land trusts; and occasionally through direct purchase of land with planning permission. The Self Build Portal (self-build.co.uk) maintained by the National Custom and Self Build Association (NaCSBA) provides information on plot availability and the self build register in each area.
Frequently Asked Questions
What is a serviced plot for custom build?
A serviced plot is a plot of land that has been prepared by a developer with the necessary infrastructure connections - mains water, drainage, electricity and gas connections to the plot boundary - ready for a custom build home to be constructed. Serviced plots remove the complexity of infrastructure provision from the custom builder and typically come with planning permission in place. They are sold by custom build developers and occasionally by local authorities.
Can I use a custom build mortgage if I am using a registered architect-designed home?
Yes. Custom build and self build mortgages cover a wide range of construction methods including architect-designed one-off homes, timber frame kit homes, and modular or modern methods of construction (MMC). Lenders do assess the construction method - some have restrictions on certain MMC types. An architect-designed home built by a main contractor for the buyer falls within the custom build definition and is assessable by specialist lenders.
Is VAT reclaimable on custom build costs?
HMRC's DIY house builders VAT refund scheme allows self build and custom build homeowners to reclaim VAT on eligible building materials and services used in the construction of a new home that will be their principal private residence. The claim is a one-off refund made after the build is complete. HMRC publishes detailed guidance on what is eligible. The VAT refund can represent a significant sum and should be factored into the project budget.
How long does a custom build project typically take?
Timescales vary significantly depending on the complexity of the design, plot preparation, contractor availability and planning conditions. A straightforward custom build using a developer's standard design range might complete in 9-12 months from plot purchase. More complex architect-designed projects can take 18-36 months from inception to completion. The mortgage offer validity should be checked against the expected build programme, with extensions negotiated if needed.
