Question 1

Do I need planning permission for a single storey rear extension?

Accepted Answer

Usually not. Most single-storey rear extensions up to 4m deep (8m for detached) fall under Permitted Development. However, PD rights can be removed in conservation areas, National Parks, AONBs, and for listed buildings. A Certificate of Lawfulness (£1,500) provides legal proof.

Question 2

How much does a single storey extension cost in 2026?

Accepted Answer

In Dorset, expect £1,800–£2,800 per m². A typical 4m x 6m (24m²) extension costs £43,000–£67,000 for the build alone. Add £2,000–£5,000 for professional fees, £8,000–£25,000 for a kitchen, and 15% contingency.

Question 3

How long does a single storey extension take to build?

Accepted Answer

The build itself takes 10–16 weeks. Add 4–12 weeks beforehand for design, planning (if required), structural calculations, and builder procurement. Total timeline from first contact to completion: 4–7 months.

Question 4

Can I build a single storey extension myself?

Accepted Answer

The design, structural calculations, and Building Regulations submission need professional input. The build itself requires experienced tradespeople — foundations, steelwork, roofing, and electrics are not DIY tasks. Our design service (£250) gives you professional plans to take to any builder.

Question 5

Does a rear extension need a party wall agreement?

Accepted Answer

If the extension is within 3m of your neighbour's property (or 6m for foundations deeper than the neighbour's foundations), you need to serve a Party Wall Notice under the Party Wall Act 1996. This is not planning permission — it is a separate legal requirement.

Question 6

What roof type is best for a single storey extension?

Accepted Answer

Flat roofs are the most common and cost-effective. A pitched roof looks more traditional but adds cost and may affect PD compliance (height limits). Lantern roofs and skylights add natural light at modest extra cost (£2,000–£5,000).

Question 7

Do I need planning permission for a two storey extension?

Accepted Answer

Almost certainly. While PD allows some two-storey rear extensions up to 3m deep with strict conditions, the majority of two-storey projects require a full planning application. We assess your property and advise on the best route.

Question 8

How much does a two storey extension cost?

Accepted Answer

In Dorset, a two-storey extension costs roughly 50–60% more than a single-storey on the same footprint (not double, because you share foundations and roof). Budget £50,000–£120,000 depending on size and specification.

Question 9

How long does a two storey extension take?

Accepted Answer

The build takes 14–20 weeks. Add 12–16 weeks for design, planning, structural calculations, and builder procurement. Total from start to finish: 7–10 months.

Question 10

Is a two storey extension worth it vs single storey?

Accepted Answer

If you need space on both levels (e.g. bigger kitchen + extra bedroom), a two-storey extension offers significantly better value per square metre. The shared foundations and roof mean the upper floor costs roughly 40% of a standalone single-storey.

Question 11

Can I build a two storey extension on a bungalow?

Accepted Answer

Yes, but this is effectively adding a full first floor and always requires planning permission. It is a significant structural undertaking that needs careful design, particularly regarding roof structure and foundations.

Question 12

Do I need planning permission for a side return extension?

Accepted Answer

Usually not, if the extension does not project beyond the existing rear wall. Side returns that stay within the existing building footprint typically fall under PD. If yours extends into the garden, standard PD rules for rear extensions apply.

Question 13

How much does a side return extension cost?

Accepted Answer

A side return only costs £25,000–£45,000. Combined with a rear extension, expect £40,000–£70,000. The cost per m² is higher than a standard rear extension because of the complexity of working in a narrow space.

Question 14

Is a side return extension worth it?

Accepted Answer

For terraced and semi-detached homes with a narrow galley kitchen, a side return is one of the best-value improvements. It typically adds 5–8% to property value and transforms daily living. The cost is modest compared to the impact.

Question 15

Can I do a side return on a semi-detached house?

Accepted Answer

Yes. Semi-detached homes often have a side return on one side. The main consideration is the party wall with your attached neighbour and the boundary wall on the other side. We design for both constraints.

Question 16

How much does a wrap-around extension cost?

Accepted Answer

In Dorset, budget £55,000–£100,000 for the build plus £3,000–£6,000 in professional fees. Wrap-arounds offer good value per m² because of the shared structure at the L-junction.

Question 17

Do I need planning permission for a wrap-around extension?

Accepted Answer

In most cases, yes — the side element typically requires planning permission. We can sometimes split the project into a PD rear element and a planning application for the side, depending on your property and timelines.

Question 18

How long does a wrap-around extension take to build?

Accepted Answer

The build takes 14–20 weeks. With design and planning, the total project timeline is 7–10 months from first contact to completion.

Question 19

Is a wrap-around better than just a rear extension?

Accepted Answer

If you have side space to use, a wrap-around creates significantly more living area for relatively modest additional cost (the side wing shares foundations and roof drainage with the rear). It is the best option for maximising ground-floor space.

Question 20

Do I need planning permission for a loft conversion?

Accepted Answer

Velux and rear dormer conversions usually fall under PD. Front dormers, hip-to-gable, and mansard conversions typically need planning permission. Properties in conservation areas and National Parks have additional restrictions.

Question 21

How much does a loft conversion cost?

Accepted Answer

From £30,000 for a simple Velux conversion to £90,000 for a full mansard. The most popular option — a rear dormer with en-suite — costs £45,000–£65,000 in Dorset.

Question 22

How long does a loft conversion take?

Accepted Answer

The build takes 8–12 weeks. Most of the work happens from above (scaffolding), so disruption to the rest of the house is less than a ground-floor extension. You can usually stay in the house throughout.

Question 23

Is my loft suitable for conversion?

Accepted Answer

Most lofts can be converted. The key factor is head height — you need at least 2.2m from the top of the ceiling joists to the ridge. If your existing head height is lower, a dormer or mansard conversion can create the required space.

Question 24

Does a loft conversion add value?

Accepted Answer

A loft conversion typically adds 10–20% to your home's value — one of the best returns of any home improvement. Adding a bedroom and bathroom (taking a 3-bed to a 4-bed) is particularly valuable.

Question 25

Do I need planning permission to convert my garage?

Accepted Answer

Usually not for integral garages. The conversion is typically an internal alteration. However, check for restrictive conditions on your property's original planning permission — some newer builds have conditions preventing garage conversions.

Question 26

How much does a garage conversion cost?

Accepted Answer

A basic single garage conversion costs £15,000–£25,000. A high-spec conversion with en-suite costs £25,000–£40,000. It is the most affordable way to add a room because the shell already exists.

Question 27

Does a garage conversion add value?

Accepted Answer

A well-finished garage conversion can add up to 10% to your home's value. However, consider the impact on parking — in areas where off-street parking is scarce, losing a garage can reduce appeal.

Question 28

What about parking if I convert my garage?

Accepted Answer

This is the key trade-off. If your property has a driveway or on-street parking is readily available, losing the garage rarely causes issues. If parking is limited, a garage conversion may need planning permission and could face objections.

Question 29

How much does a kitchen extension cost?

Accepted Answer

Budget £55,000–£130,000 total, including the extension build, kitchen units, appliances, and professional fees. The extension itself costs £36,000–£84,000 depending on size; the kitchen fit-out is £10,000–£33,000 on top.

Question 30

Should I design the kitchen or the extension first?

Accepted Answer

Design them together. The kitchen layout determines where services (water, gas, electrics) need to go, which affects the structural design. We design the extension and kitchen layout as one integrated project.

Question 31

What size kitchen extension do I need?

Accepted Answer

For a kitchen-diner with an island, you need at least 4.5m width and 5m depth (22.5m²). For a simpler layout without an island, 4m x 4m (16m²) works well. We help you determine the right size based on your property and how you cook and eat.

Question 32

Can I relocate the kitchen to the extension?

Accepted Answer

Yes. Many homeowners move the kitchen into the new extension and repurpose the old kitchen as a utility room, study, or playroom. This gives the best result but costs more because you are fitting out two rooms.

Question 33

How much does it cost to knock through a wall?

Accepted Answer

Removing a non-load-bearing wall costs £500–£1,500. Removing a load-bearing wall costs £2,500–£6,000 including the steel beam. Making good (plastering, flooring, decoration) adds £2,000–£5,000. Total for a typical open-plan conversion: £5,000–£12,000.

Question 34

Do I need planning permission to remove an internal wall?

Accepted Answer

No. Internal alterations do not require planning permission. If the wall is load-bearing, you need Building Regulations approval for the structural work, but this is a separate process from planning.

Question 35

How do I know if a wall is load-bearing?

Accepted Answer

As a general rule, walls that run perpendicular to the floor joists above are likely load-bearing. Walls parallel to the joists are more likely to be non-load-bearing. However, this is not always the case — a structural engineer should confirm before any wall is removed.

Question 36

Can I create open-plan living without an extension?

Accepted Answer

Yes. Many homes have enough ground-floor space — it is just divided by walls. Our Vision Draft (£29.99) shows what your home could look like with walls removed, before you spend anything on structural work.

Question 37

Is an orangery better than a conservatory?

Accepted Answer

For year-round use, generally yes. Orangeries are warmer in winter and cooler in summer due to solid walls and better insulation. They also look more integrated with the house and add more value. Conservatories are cheaper but can be uncomfortable in extreme temperatures.

Question 38

How much does an orangery cost?

Accepted Answer

From £30,000 for a small (12–16m²) orangery to £100,000 for a large (25–35m²) design. This is more than a conservatory (£10,000–£30,000) but less than a full brick extension of the same size.

Question 39

Do I need planning permission for an orangery?

Accepted Answer

Usually not. Most orangeries fall under Permitted Development. The same PD rules as single-storey extensions apply. If your property is in a conservation area, an orangery's solid walls are often more acceptable than a glazed conservatory.

Question 40

Does an orangery need Building Regulations?

Accepted Answer

If less than 75% of the roof is glazed (which is the case for most orangeries), Building Regulations apply in full. This means foundations, insulation, drainage, and electrical work must comply — same as a standard extension.

Question 41

Do I need planning permission for a porch?

Accepted Answer

Not if it is under 3m² (external), under 3m high, and at least 2m from a highway boundary. Larger porches are treated as extensions and may need planning permission depending on PD rules.

Question 42

How much does a porch extension cost?

Accepted Answer

A simple enclosed brick porch costs £5,000–£12,000. Oak-frame and high-spec porches cost £8,000–£15,000. Open canopies start from £2,000.

Question 43

Does a porch add value?

Accepted Answer

A porch adds modest value (1–3%) but significantly improves kerb appeal and the daily experience of entering your home. It is a practical improvement rather than a value-add project.

Question 44

Can I add a second floor to my bungalow?

Accepted Answer

Yes, but it always requires planning permission and significant structural work. You will need to strengthen or replace the foundations and wall structure. It is a major project but can double your living space.

Question 45

How much does it cost to extend a bungalow?

Accepted Answer

A rear extension costs £35,000–£65,000. A dormer conversion costs £40,000–£65,000. Adding a full upper floor costs £80,000–£150,000. The right option depends on how much space you need and your budget.

Question 46

Can I convert my bungalow loft?

Accepted Answer

If the ridge height is adequate (minimum 2.2m from top of joists to ridge), yes. Most bungalow loft conversions add dormer windows to create enough headroom and floor area for habitable rooms.

Question 47

Will neighbours object to my bungalow becoming a house?

Accepted Answer

Potentially. In areas with many bungalows (especially retirement areas), neighbours may object to the change in character. Sensitive design — stepping the upper floor back from the boundaries, using dormer windows rather than a full second storey — can mitigate objections.

Question 48

How much does a basement extension cost?

Accepted Answer

Cellar conversions cost £1,500–£2,500 per m² (£30,000–£50,000 for a typical cellar). New basements cost £3,000–£5,000 per m² (£90,000–£150,000 for 30m²). It is the most expensive per-square-metre option but can be the only option on restricted sites.

Question 49

Is a basement conversion worth it?

Accepted Answer

It depends on your property value and alternatives. In high-value areas where you cannot extend outwards, a basement can be cost-effective. In areas where a rear extension is possible, extending above ground is almost always cheaper.

Question 50

Do I need planning permission for a basement?

Accepted Answer

Converting an existing cellar usually falls under PD. Excavating a new basement beneath the existing footprint may also be PD. Any work that extends beyond the existing footprint needs planning permission.

Question 51

Can any builder do a basement conversion?

Accepted Answer

No. Basement work — especially underpinning and waterproofing — requires specialist contractors. Using a general builder for basement work is a significant risk. We can introduce you to specialist basement contractors through our builder network.

Question 52

How much does a single storey extension cost per m² in 2026?

Accepted Answer

£1,800–£2,800 per m² for the build alone, depending on specification. Standard spec averages £2,000/m², high spec £2,500/m². This does not include the kitchen, flooring, professional fees, or contingency.

Question 53

What is the cheapest single storey extension?

Accepted Answer

The cheapest option is a basic 3m × 4m (12m²) rear extension with a flat roof: approximately £22,000–£34,000 for the build. With all costs included, budget £40,000–£55,000 minimum.

Question 54

How can I reduce extension costs?

Accepted Answer

Keep the design simple (rectangular plan, flat roof), avoid moving drainage, choose standard materials, and get at least three builder quotes. Our design service (£250) optimises the layout before you commit to a builder, potentially saving thousands.

Question 55

Should I get a fixed price or day rate from my builder?

Accepted Answer

Always get a fixed price based on detailed drawings and a specification. Day rates make budgeting impossible and give the builder no incentive to work efficiently. Our Building Regulations drawings give builders enough detail to quote accurately.

Question 56

Is a two storey extension better value than single storey?

Accepted Answer

Yes, if you need space on both floors. The upper floor costs roughly 40% of a standalone single-storey because you share foundations and roof. The cost per m² of usable space is significantly lower.

Question 57

Does a two storey extension need planning permission?

Accepted Answer

Almost always. PD allows some two-storey rear extensions up to 3m deep with strict conditions, but the majority need a full planning application.

Question 58

How much does a loft conversion cost in 2026?

Accepted Answer

From £30,000 for a Velux to £90,000 for a mansard. The most popular option — a rear dormer with en-suite — costs £48,000–£72,000 all-in.

Question 59

Which loft conversion type is cheapest?

Accepted Answer

A Velux/rooflight conversion is cheapest (£30,000–£45,000) because it does not alter the roof shape. However, it only works if you already have adequate headroom under the existing ridge.

Question 60

Does a loft conversion add more value than an extension?

Accepted Answer

A loft conversion typically adds 10–20% to property value, compared to 5–10% for a ground-floor extension. Adding a bedroom + bathroom (3-bed to 4-bed) is one of the highest-ROI improvements.

Question 61

Is a garage conversion cheaper than an extension?

Accepted Answer

Significantly cheaper. An extension costs £1,800–£2,800/m² because you are building from scratch. A garage conversion costs £800–£1,500/m² because the walls and roof already exist.

Question 62

How much does a kitchen extension cost in total?

Accepted Answer

Budget £63,000–£140,000 for a 24m² kitchen extension including the build, kitchen fit-out, appliances, and all professional fees. The range depends primarily on kitchen specification.

Question 63

Should I budget for the extension or kitchen first?

Accepted Answer

Set a total budget, then allocate 60–70% to the extension build and professional fees, and 30–40% to the kitchen fit-out. Do not spend 90% on the build and have nothing left for a decent kitchen.

Question 64

How much do architect fees cost in the UK?

Accepted Answer

Traditional architects charge 8–15% of the build cost. For a £60,000 extension, expect £4,800–£9,000. Fixed-price services like PlanBuildCo charge £250–£2,200 depending on what you need.

Frequently Asked Questions

Extension types

Costs

Planning permission

Comparisons

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