Not all annexes are treated equally by mortgage lenders. The type and configuration of your annexe will significantly influence which lenders are available and what terms they offer.
Attached Annexes
An annexe that is physically attached to the main property and shares internal access is generally the most straightforward for remortgaging. Many mainstream lenders will treat this similarly to a large property, particularly if the annexe cannot be sold separately.
Detached Annexes
A detached annexe in the garden or grounds of the main property can be more challenging. Lenders may be concerned about the potential for the annexe to be sold or let separately, which could affect the security of their loan. Some lenders will accept detached annexes provided certain conditions are met, such as shared utilities or a restriction preventing separate sale.
Converted Outbuildings
Garages, barns, or other outbuildings converted into living accommodation may be treated differently depending on the quality of the conversion, whether planning permission was obtained, and whether building regulations were followed.
The degree of self-containment is a key consideration for lenders. An annexe with its own kitchen, bathroom, and separate entrance is more likely to be viewed as a separate dwelling, which some lenders may not accept under a standard residential mortgage.
Lenders will want to be satisfied that your annexe has the appropriate planning permission and complies with building regulations. Missing or inadequate documentation in this area is one of the most common reasons for complications when remortgaging a property with an annexe.
Planning permission. Most annexes require planning permission, particularly if they involve new construction or a change of use. Some smaller projects may fall under permitted development rights, but this depends on the size, location, and nature of the work. Your local planning authority can confirm whether permission was required and granted.
Building regulations. Regardless of whether planning permission was needed, building regulations approval is almost always required for habitable accommodation. This covers structural integrity, fire safety, insulation, ventilation, and electrical and plumbing standards. A completion certificate from building control is the key document lenders will look for.
Lawful development certificates. If your annexe was built some time ago without formal planning permission, it may be possible to obtain a Certificate of Lawful Development (CLEUD) if the use has been continuous for four or more years. This can regularise the planning position and reassure lenders.
Before applying to remortgage, check that you have all the necessary certificates and approvals in place. If anything is missing, take steps to obtain it before you apply.
One factor that can significantly affect your remortgage options is whether your annexe has a separate council tax bill.
If the annexe has its own council tax band, some lenders may view it as a separate dwelling rather than part of the main property. This can move it outside the scope of a standard residential mortgage and into the territory of a multi-unit or investment property, which fewer lenders may be willing to finance under standard terms.
Conversely, if the annexe is assessed as part of the main property for council tax purposes, it is more likely to be treated as a single residential unit, which simplifies the remortgage process.
If your annexe currently has separate council tax billing but you believe it should be assessed as part of the main property, you may be able to appeal to the Valuation Office Agency (VOA) to have it reclassified. This is not always possible, but it is worth exploring if separate billing is creating difficulties with your remortgage.
It is also worth noting that annexes used by family members may be eligible for council tax discounts or exemptions in some circumstances. Your local authority can advise on this.
