Double-storey extensions in Knowle

Planning your two-storey extension in Knowle

Planning permission from Solihull Council is the first hurdle for most double-storey extensions in Knowle. Householder applications have an eight-week target for a decision, and Building Regulations approval and the Party Wall Act may also apply.

Party wall notices take one or two months to run, so they're best served as soon as planning is granted.
A side extension of more than one storey always needs a householder planning application.
Under permitted development, a rear extension of more than one storey can project no more than 3 metres and must be at least 7 metres from the rear boundary.

Postcode district: B93
Planning and building control: Solihull Council
From our West Bromwich base: 14 miles

Options to consider in Knowle

Building over an existing extension

Adds a first floor on top of an existing single-storey extension or attached garage. It can cost less because the footprint already exists, but a structural engineer must check the existing foundations and walls first, and they sometimes need strengthening. The old flat roof comes off and the new floor is tied into the main house.

Two-storey side extension

Built over the side of the house, often where a driveway or old garage sits. It can create a garage, utility or study downstairs with a double bedroom above. Councils often expect the upper floor to be set back from the front and the roof to sit lower than the main ridge, so the design needs care to win approval.

Double-storey extensions prices in Knowle

Prices in Knowle match the rest of our area: £52,000–£135,000 depending on size and specification. A two-storey side extension on a three-bed semi, about 32 m² over two floors: usually £68,000–£88,000.

Guide prices for double-storey extensions
Option	Guide price	Good to know
Compact two-storey rear (20–28 m² total)	£52,000 – £72,000	Bigger kitchen below, bedroom or bathroom above
Two-storey side or rear (30–40 m² total)	£68,000 – £98,000	The usual size on a three-bed semi
Large or combined side and rear (45 m²+)	£95,000 – £135,000	More steel, a complex roof and a longer programme

Guide ranges include VAT where it applies. A free survey turns this guide into a fixed, itemised price.

Questions about double-storey extensions in Knowle

How much does a double-storey extension cost?

In the West Midlands, most double-storey extensions cost between £52,000 and £135,000, including VAT where it applies. A typical side extension on a three-bed semi, around 32 m² across both floors, usually costs £68,000–£88,000 built to a plastered finish. Kitchen units, a bathroom suite, flooring and decorating are priced separately, so you can choose them to suit your budget.

Which postcodes in Knowle do you work in?

We cover B93 and the streets around them. If you're on the edge of Knowle, neighbouring Dorridge and Balsall Common are covered too.

What paperwork will I have at the end?

You'll get the building control completion certificate, the electrical installation certificate, your planning decision notice and the manufacturers' guarantee documents for windows, doors and roof products, with their terms set out in your quote. Keep these together, as a buyer's solicitor will ask for them when you sell. Ask us for current insurance details with your quote.

Does Solihull Council need to approve my two-storey extension?

Usually both. Most two-storey extensions need a planning application to Solihull Council, and the structural work needs Building Regulations approval from its building control team or a registered building control approver.

Also covering nearby

Other work we do in Knowle

Want a guide figure first? Use our quote tool for your Knowle extension, then book a survey for a fixed price for the agreed specification.