HMORefurbishment
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Extra rooms and layouts

Extensions for extra rooms

Rear and side extensions that add bedrooms or a bigger kitchen to a shared house.

  • Free site visit and measured survey
  • Built to the council’s HMO standards
  • Certificates and photos at handover
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Three-storey house under full scaffolding with guardrails and brick guards during refurbishment works
In short: An HMO extension adds space to a shared house, usually a ground-floor bedroom with ensuite or a bigger communal kitchen. It needs the right planning route, building regulations approval and a fire strategy that still works for the whole house once the space is added.

What do extensions for extra rooms include?

  • Planning route check and drawings
  • Foundations, structure and roof
  • Kitchen or bedroom fit-out
  • Ensuite drainage and extraction
  • Fire separation and detection extended to the new space
  • Heating, insulation and glazing
  • Party wall coordination where needed
  • Building control completion

When do landlords need it?

  • A kitchen too small for the number of sharers
  • Adding a ground-floor room
  • Moving to more sharers with consent

What rules apply in each UK nation?

The law differs between England, Wales, Scotland and Northern Ireland, and councils publish their own HMO standards on top. These are the points that usually matter for this work.

England

  • 3–6 unrelated sharers is use class C4; changing from a family house is usually permitted development unless an Article 4 direction applies.
  • Building regulations cover structural changes, new partitions, ensuite drainage, fire-resisting construction and notifiable electrical work.
  • Fire precautions follow a risk assessment; the LACORS Housing – Fire Safety guide (2008) is guidance, not law, but many councils base their standards on it.
  • National rules ask for an adequate number of bathrooms, WCs and basins and suitably located kitchens; numeric ratios are set by each council.

All HMO rules for England

Wales

  • 3–6 sharers is use class C4, and in Wales changing a house to C4 always needs planning permission; only C4 back to C3 is permitted development.
  • Building regulations cover structural work, partitions, drainage, fire-resisting construction and electrics; confirm with building control whether the conversion is a material change of use.
  • Fitness for human habitation rules require mains-powered, interlinked smoke alarms on every storey and CO alarms where there is a gas, oil or solid-fuel appliance.
  • Kitchen and bathroom ratios are set in each council’s HMO standards.

All HMO rules for Wales

Scotland

  • Scotland has no C4 use class: up to 5 residents can fall within Class 9 (houses), and HMO planning policy is set by each council, some of which require permission at lower numbers.
  • A building warrant may be needed for a change of use or for installing a fire alarm system; check with the council’s building standards service.
  • The tolerable standard requires interlinked smoke alarms in the main living room and circulation spaces and a heat alarm in the kitchen; licensed HMOs must meet the council’s higher standard.
  • Kitchen, WC and bathroom ratios come from council standards; one WC and one bath or shower per 5 people is a common figure.

All HMO rules for Scotland

Northern Ireland

  • All new HMOs need planning permission; councils such as Belfast apply HMO policy areas and limits on concentration.
  • New HMOs need building control approval as well as planning permission.
  • The NIFRS HMO Fire Safety Guide (July 2026) usually expects Grade D1 interlinked detection in smaller shared houses and a Grade A system with more than 6 occupants or over 200 m².
  • Kitchens, bathrooms and WCs must meet the 2019 living accommodation standard regulations and licence conditions.

All HMO rules for Northern Ireland

How much do extensions for extra rooms cost?

UK typical budget ranges. See local pages for regional guides.
ItemUK typicalPer
Single-storey extension, about 15 m²£35,000 – £60,000project
Single-storey extension per m²£1,800 – £4,000m²

Typical time on site: 8–14 weeks. Your fixed price follows a site visit; use the guide-price tool for a figure for your house.

How the job runs

  1. Free site visit and measured survey.
  2. Itemised written quote and programme.
  3. Works with one point of contact and photo updates.
  4. Handover with certificates, drawings and photos.

Questions about extensions for extra rooms

Can I extend an HMO under permitted development?

Some extensions to houses are permitted development, but rules differ for HMOs and by nation and council. We check the address before design.

Is a kitchen extension worth it?

Often, when the existing kitchen limits how many people the council will allow. A bigger kitchen can unlock an extra room.

Will the extension affect neighbours?

Possibly, if it is on or near a boundary. Party wall procedures may apply in England and Wales.

Do you handle building control?

Yes, from application to completion certificate.

Related services

Where we work

Choose a nation and area for local rules, postcodes and regional prices.

England

Wales

Scotland

Northern Ireland

Planning HMO works?

Free site visit, then a fixed written quote itemised against your council’s standards.

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