Rear or side extension: which suits your house?

Start with the room you want to use

Equal floor area does not mean equal usable space.

Write a short brief describing what does not work today. Perhaps chairs block the route to the garden, the kitchen is too narrow for two people, or an office needs separation from family noise. Give each issue a priority. Then ask which layout removes it without creating another problem. An extension can be larger yet leave the original bottleneck untouched.

A rear extension is worth testing when the main need sits behind the existing house: a deeper dining area, another living zone or a clearer garden connection. A side option is worth testing when widening the current room would improve its proportions or allow a separate utility or working space. These are design starting points, not promises that either arrangement fits your property.

Draw the existing rooms as well as the new footprint. Include door swings, stairs, kitchen cabinets, furniture and the routes between them. Mark what must stay. A diagram showing only the new rectangle can hide a narrow entrance, awkward corner or lost window in the old house. Use the Rugby extension service to discuss that complete layout rather than treating the new structure in isolation.

Test width and depth with the same furniture

A long narrow addition and a shorter wide one behave differently.

Use a labelled hypothetical comparison before discussing actual construction costs. A 6m by 3m rectangle has 18 square metres of plan area. A 2m by 9m rectangle also has 18 square metres. Those figures are simple geometry, not permission limits, usable internal measurements or a suggestion that either fits your plot. Walls and connections still need to be drawn accurately.

Place the same table, sofa or desk in both sketches at scale. Draw chairs pulled out and a person moving past them. Show where daylight enters and where the route from the kitchen to the garden runs. Ask whether the new space works as a room or mostly becomes circulation. Furniture sizes should come from the items you intend to use, not an optimistic visualisation.

Also sketch a smaller option that changes the existing layout. A modest addition combined with a carefully designed opening may solve the brief differently from a larger standalone room. Get structural advice before assuming a wall can be removed. The structural alterations page explains the relevant service; this comparison does not establish which walls support your house.

Keep light, garden and side access on the plan

Space used for access still has a job, even when it looks empty.

Walk the current route from the front of the property to the garden. List the things carried along it: bins, bicycles, tools, garden furniture and deliveries. If a side extension closes that route, show where each will go afterwards. A passage used occasionally can still be important. Do not describe all side space as wasted simply because it is not a habitable room.

For a rear option, draw the remaining garden and patio rather than only the additional floor area. Check where outdoor seating, storage and maintenance access will sit. Consider the view from the original rooms as well as the new one. Neither design should be chosen from a photograph of another house, because orientation, neighbours and existing windows change the result.

In a Rugby layout review, mark windows that the extension would cover or move. Ask the designer to assess daylight through the complete house, including rooms behind the new area. Rooflights or larger doors are options to discuss, not a guarantee that an old room stays bright. Their position should be considered with privacy, ventilation, shading and the furniture arrangement.

Check Rugby planning against the actual house

Rear and side permitted development have different limits and shared conditions.

Planning Portal summarises qualifying single-storey rear depths as up to 4m for detached houses or 3m for other houses. Larger 8m or 6m limits use a prior-approval route where eligible. A qualifying side extension is single storey, up to 4m high and no wider than half the original house. These are screening limits, not automatic permission.

The original-house measurement matters. GOV.UK's technical guidance explains how previous additions and joined enlargements affect the assessment. A wraparound or staged rear-and-side scheme cannot simply be treated as two independent allowances. Ask the designer to check the complete geometry against the guidance. There is no universal 2.8m side width that applies to every property.

For a Rugby address, the council says rights can be adapted or removed and identifies separate issues for listed buildings and conservation areas. Check the planning history and relevant restrictions before relying on permitted development. The council offers a paid pre-application advice route. Our Rugby planning guide and side-extension guide help organise that enquiry.

Check the guidance: Planning Portal: Extension planning permission, GOV.UK: Householder permitted development technical guidance, Rugby Borough Council: Do I need planning permission?.

Assign technical and neighbour checks separately

Planning permission does not settle building regulations or Party Wall duties.

GOV.UK states that building regulations cover extensions and distinguishes technical approval from planning permission. Agree who prepares the technical design, appoints building control and coordinates inspections. Ask the designer and builder to identify the structure, roof, insulation, drainage and service interfaces that need resolution. Keep responsibility attached to actual work packages rather than assuming a planning drawing contains every construction detail.

The Party Wall route is another check. GOV.UK identifies work to shared structures, building on a boundary and digging below and near a neighbour's foundations among the relevant situations. Have the actual drawings and excavation proposal assessed. Being a side extension or sharing a boundary does not by itself tell you that a particular surveyor appointment is automatically required. The Party Wall guide explains the separate process.

Put approvals and neighbour matters into a short responsibility schedule. For each one, record the person handling it, the document required and the point at which it must be resolved. Include any further property-specific consent identified by your advisers. This is more useful than a generic promise that someone will deal with the paperwork after work has begun.

Check the guidance: GOV.UK: Building regulations approval, GOV.UK: Party walls and building work, GOV.UK: Work you must tell your neighbour about.

Compare the complete work before comparing prices

Neither extension position is automatically the cheaper choice.

Give bidders the same drawing revision and finish specification for each option. Ask for foundations, structural connections, roof, glazing, services, insulation, internal finishes, waste and external reinstatement to be identified. Include design and approval costs separately where they are outside the building price. Use the quotation checklist to check exclusions and assumptions before judging the headline.

For budget background, use the rear extension guide and extension cost per square metre guide. Their researched figures do not establish your payable price. Ask what investigation remains, which items are provisional and how changes will be authorised. A lower figure with unresolved drainage, glazing or making good cannot be compared fairly with a defined complete-room proposal.

Ask for a proposed sequence as well as the price. Identify decisions still needed, supplier dependencies and which existing rooms will be affected during each phase. Compare disruption to daily life alongside the finished layout; do not turn a general programme into a guaranteed completion date.

Keep tax explicit. GOV.UK says most building work to existing homes uses standard 20% VAT, with exceptions. For hypothetical arithmetic only, £10,000 excluding VAT becomes £12,000 including 20% VAT: £10,000 plus £2,000. This is neither a national benchmark nor a Belmax quotation. Ask each bidder to state the applicable tax treatment and final payable total.

Finish your brief with the preferred room arrangement, the garden and access you want to retain, your overall budget and any drawings already prepared. Include photographs of both sides of the decision. If the main aim is an open-plan kitchen, the kitchen extension guide addresses that additional specification. Choose an option only after its useful space, unresolved risks and complete scope are clear. For alternatives using existing rooms, compare the scope boundaries in the Coventry renovation guide; its budget evidence is separate from your Rugby extension.

Check the guidance: GOV.UK: VAT for builders.