How much does a granny annexe cost?

The cost of a granny annexe depends on the size, building type, specification, glazing, kitchen, shower room, drainage, exterior finish and optional extras. TRJ Construction’s calculator gives a guide price before a detailed site survey and quotation.

What does the granny annexe price calculator include?

The calculator includes building type, width, depth, external area, main doors, extra windows, kitchen, shower room, drainage, armoured cable, exterior finish, building control, planning support and optional extras such as air conditioning, decking, skylights, sedum roof and drainage solutions.

Is the calculator price a fixed quotation?

No. The calculator provides a guide estimate only. Final pricing depends on drawings, site access, ground conditions, service routes, drainage, planning requirements, building control and final specification.

Can I send my calculator estimate to TRJ Construction?

Yes. The calculator is designed to send the completed form and estimated guide price to TRJ Construction so the team can review your project details and follow up.

Do granny annexes need planning permission?

Many granny annexes require planning consideration because they can include sleeping accommodation, a kitchen, bathroom and independent living facilities. TRJ Construction can advise on the likely route for your project.

Which areas does TRJ Construction cover for granny annexes?

TRJ Construction builds granny annexes across Hertfordshire, Buckinghamshire, Essex and North London, including areas such as Watford, St Albans, Barnet, Cheshunt and nearby locations.

Granny Annexe Price

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Granny Annexe Prices & Cost Calculator

Customer Details

Full Name *

Telephone *

Email *

Project Address *

Building Type & Size

Choose Type of Building *

Width *

Depth *

Calculated External Area 0.0 sqm

Doors, Windows & Rooms

Main Doors

Extra Windows

Kitchen

Shower Room

Services & Exterior

Extra drainage after 10m included

Extra drainage is £150 per metre.

Extra armoured cable after 15m included

Extra armoured cable is £135 per metre.

External Front Finish Sides and back: cement particle board with grey/anthracite K-render included.

Compliance & Surveys

✓ Building control +£1,400

✓ Soil test +£500

Planning permission support +£2,000

Optional Extras

Air conditioning unit +£1,650 Storage room with secret door +£975 Mini sewage pump for drainage solution up to 25m run +£2,200 Soakaway 1.5m x 1.5m x 1m +£800 Sedum roof £185 per sqm Skylight 1200mm x 1200mm +£1,500 each Electric opening upgrade for skylights +£500 each Decking from £145 per sqm

Number of Skylights

qty

Decking Type

Decking Area

sqm

Included as standard:

Select a building type to see what is included.

Upload Files

Optional: add up to 5 pictures, sketches or PDF drawings.

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Please complete name, address, email, telephone number, building type, width and depth.