Converted MUFB HMO mortgages

What is a converted MUFB HMO mortgage?

A converted MUFB HMO mortgage is buy to let finance on a building that has been converted into flats or units, usually on a single utility supply and under HMO licensing, which lenders assess as a house in multiple occupation (HMO) rather than as a multi-unit freehold block (MUFB).

On paper the building can look like any block of flats on one freehold title. What changes the lending is how it was converted and how it is licensed. In our experience most lenders underwrite this type of block as an HMO, so the HMO criteria, loan-to-value (LTV) bands and valuation methods apply, not the MUFB ones.

A purpose-built block, or a conversion with separate utilities that meets building regulations and needs no HMO licence, is normally a standard MUFB case. That is covered on our MUFB mortgage page. A whole block bought as a commercial investment, often six or more units, is discussed in our article on a commercial mortgage for a block of flats.

This page describes the position in England. Wales uses the same Housing Act 2004 framework with its own licensing rules, and Scotland has a separate HMO licensing regime, so the licence evidence a lender asks for differs by nation.

Why lenders treat a converted block as an HMO

Two legal routes bring a converted building into the HMO regime, and either one moves the mortgage onto HMO criteria.

• Section 257 HMO. Under section 257 of the Housing Act 2004, a building converted into self-contained flats is an HMO where the conversion did not meet the appropriate building standards and still does not, and fewer than two-thirds of the flats are owner-occupied. For conversions completed before 1 June 1992 the benchmark is the standard set by the Building Regulations 1991; for later conversions it is the building regulations in force when the work was done.
• Units that share facilities. Where some units are not self-contained, for example bedsits or studios sharing a kitchen or bathroom, the building can meet the converted building test or the standard test in section 254 of the same Act. In England, five or more people forming two or more households brings it within mandatory licensing.

A section 257 HMO sits outside the description used for mandatory licensing in England (the Licensing of Houses in Multiple Occupation (Prescribed Description) (England) Order 2018), so a licence on that type of block normally comes from a council additional or selective licensing scheme. Either way, lenders read the licence and the conversion history as evidence that the building is an HMO.

A single utility supply points the same way. With one supply for gas, electricity or water, the flats cannot be sold one by one without work, so the valuer cannot rely on individual flat sales and the lender looks at the building as one income-producing asset.

Sources: Housing Act 2004, section 257 and SI 2018/221, article 4, legislation.gov.uk, checked 1 October 2026.

How the lending differs from a purpose-built MUFB

The same building can be offered on very different terms depending on whether a lender treats it as an MUFB or as an HMO, and the three things that move most are the criteria, the LTV and the valuation basis.

The table compares the two positions on the cases we arrange. Lender criteria vary and change, so it describes our experience rather than a market rule.

Converted MUFB HMO mortgage criteria

Criteria on a converted block follow the lender's HMO rules, with extra attention to the licence, the lawful use of the building and how far the conversion falls short of building regulations.

On LTV, HMO lending commonly runs between 60% and 75%, and products above that are uncommon and usually depend on a residential valuation that a converted block on one utility supply rarely gets. The 85% and 80% figures we see on purpose-built MUFBs do not carry across to a block underwritten as an HMO.

How a converted HMO block is valued

The valuation method usually has a larger effect on the loan than the interest rate, and on a converted block it is chosen from the HMO methods rather than the MUFB ones.

• Bricks and mortar valuation. Market value against comparable sales of similar buildings. It suits smaller HMOs that still compare with ordinary residential stock, which a converted block on one supply often does not.
• Hybrid valuation. Blends comparable evidence with the income the property produces as an HMO, without a full commercial investment valuation.
• Yield-based valuation (MV1). Values the building on its rental income and a market yield, like a commercial investment. It is common on larger HMOs and on converted blocks that can only be sold as a whole, and it usually needs a local valuer with HMO evidence.

A purpose-built MUFB is valued on a block or aggregate basis instead. Aggregate valuation, which adds up the value of each flat as if sold separately, usually needs each flat to have its own utilities and to be saleable on its own, so it is rarely the basis on a single-supply conversion. Our guide to HMO mortgage valuations explains each method in more detail.

Licensing, planning and building standards

Lenders want evidence that the building is licensed where it needs to be, lawfully used for the number of units it has, and safe for the people living in it.

Licensing

England has three licensing regimes and one building can fall under more than one:

• Mandatory licensing for HMOs occupied by five or more people forming two or more households, other than section 257 blocks and purpose-built flats in blocks of three or more.
• Additional licensing, set by individual councils for HMOs outside the mandatory scheme, which is how many section 257 blocks come to be licensed.
• Selective licensing, set by councils for privately rented homes in a defined area.

Lenders usually ask for the licence, or written confirmation from the council that none is needed. A licence lasts no more than five years, so its renewal date matters on a remortgage.

Planning

Lenders check that the current use is lawful, through planning permission for the conversion or a certificate of lawful use. Large HMOs with seven or more occupants are usually sui generis in planning terms, and Article 4 directions in some areas remove permitted development rights for HMO conversions.

Building standards and fire safety

A section 257 block is, by definition, a conversion that falls short of the relevant building standards. The valuer and lender look at fire separation, fire doors, alarms and escape routes, and at any works the council requires as a licence condition. Outstanding works can reduce the valuation or lead to a retention until they are done.

Our HMO mortgage guide covers licensing and planning in England and Wales in more depth.

Experience, income and borrower structure

Experience and personal income matter more on a converted HMO block than on a standard MUFB, and the bar rises with the number of units.

On the cases we arrange, where a lender uses a yield-based (MV1) valuation and the borrower has no HMO experience, we see no minimum personal income requirement on six units or fewer. For a large HMO of seven or more units, lenders commonly look for a personal income of around £50,000, because even the more flexible lenders apply tighter experience requirements above six units. Strong HMO letting experience can widen the choice of lender.

Converted blocks can be bought in personal names or through a limited company, including a special purpose vehicle (SPV), subject to each lender's rules. A first-time HMO investor can be considered, usually with fewer lenders and a larger deposit. Our pages on HMO mortgages with no experience and large HMO mortgages go further into both.

Running costs lenders allow for

A converted HMO block usually carries costs that a purpose-built MUFB passes to its tenants, and lenders and valuers allow for them when they assess the rent.

• Utilities. On a single supply the landlord normally pays the bills and builds them into the rent, so the net income is lower than the headline rent.
• Council tax. Where units share facilities, the owner is usually liable for council tax. Self-contained flats are normally banded separately, with the occupier paying.
• Licensing and compliance. Licence fees, fire safety testing, management and repairs to communal areas all come out of the income.

Clear evidence of the rent roll, the tenancy agreements and who pays which bill makes the underwriting quicker and the valuation easier to support.

Rates and costs

There is no single rate for a converted MUFB HMO mortgage: pricing depends on the lender, the LTV, the valuation method, the number of units and your experience.

HMO pricing is usually above standard buy to let, and fees can be a flat amount or a percentage of the loan. Any rate we quote carries the date it was checked and is subject to status and lender criteria. An adviser compares the total cost of each option over the fixed or initial period, not only the headline rate.

When a converted block can be treated as an MUFB

A converted block can move from HMO criteria to MUFB criteria if the reasons it is an HMO fall away, and that can change both the valuation and the LTV available.

Bringing the conversion up to the relevant building standards, or two-thirds or more of the flats becoming owner-occupied on long leases, takes a building outside section 257. Separating the utilities for each flat can open up lenders that need individual supplies. Work like this usually needs funding before a long-term mortgage, for example through a refurbishment loan or a bridging loan, with the exit onto an MUFB mortgage once the works are signed off. Whether a lender then accepts the block as an MUFB is a case-by-case decision.

How a converted MUFB HMO mortgage is arranged

1. The building. Number of units, which are self-contained, utility supplies, conversion history, licence and planning position.
2. You. Experience, income, ownership structure and the rent roll.
3. Lender selection. Lenders whose HMO criteria accept a converted block of this size, matched to the likely valuation method.
4. Agreement in principle and valuation. The valuer reports on the HMO basis and on any works needed.
5. Underwriting, offer and completion. Licence, planning and tenancy evidence are checked, the offer is issued and your solicitor completes.