01 — We do this
Foundations
The difficult part is already done.
- Site set out
- Ground screws installed
- Steel ring beam levelled and set
Self-build garden annexe kits — UK
The engineering is ours.
The build is yours.
A self-build garden annexe with the difficult part already finished. We set out the site, drive the ground screws and level the steel ring beam. You take it from there — on a foundation that is already dead level, already load-tested, and already signed off.
Where this sits
The permanence of conventional construction. The speed people associate with factory-built annexes. A price between the two.
- Solid A real building, not a frame with a skin.
- Insulated formwork, reinforced and filled with concrete. Doors and windows are hung in a poured wall, not a panel. It is built to read as a small house, not a pod, a cabin or a garden room.
- Fast Built at the pace of a drop-in unit, without dropping the standard.
- Ground screws go in without excavation and take load immediately — no dig, no muck away, no slab curing before you can start. The wall system goes up dry and is poured once, so the wet trades are few and short.
- Sensibly priced Between a bare self-build shell and a turnkey factory annex.
- You are not paying a factory margin on every visible finish. Neither are you buying a pile of components with the difficult engineering left unresolved. The hard part is settled; the part you have opinions about is still yours.
- Yours to finish Specified by you, not by a production line.
- You choose the kitchen, the bathroom, the cladding and the layout of the last 20%. Nobody hands you a fixed specification because it suits their production line. Spend where you want to spend, save where you want to save.
02 — You do this
Shell
From level steel to weatherproof.
- Build the Creo block walls
- Concrete pour
- Lay roof frame and insulated deck
- Fit EPDM membrane
- Install windows and doors
03 — Your choices
Fit-out
Specify it how you want to live in it.
- External cladding
- Electrics
- Plumbing and drainage
- Heating
- Kitchen
- Bathroom
- Decoration
How it works
Three stages. One handover.
-
01
We do this
Foundations
The difficult part is already done.
- Site set out
- Ground screws installed
- Steel ring beam levelled and set
-
02
You do this
Shell
From level steel to weatherproof.
- Build the Creo block walls
- Concrete pour
- Lay roof frame and insulated deck
- Fit EPDM membrane
- Install windows and doors
-
03
Your choices
Fit-out
Specify it how you want to live in it.
- External cladding
- Electrics
- Plumbing and drainage
- Heating
- Kitchen
- Bathroom
- Decoration
Drainage and utility routes need planning before anyone turns a screw. We will walk the site with you first.
On site
Not a visualisation.
The wall system, the pour and the annex below are all photographed on real jobs. Where an image is from a different build to the one described, the caption says so.
01 — We do this
Set out and levelled
The perimeter goes down to the drawing before a single course is laid.
-
Perimeter set out on the cleared plot -
First course, boundary side -
Steel landed onto the wall line -
Guided in by hand
02 — The wall system
Formwork, then concrete
The blocks are dry-stacked and poured once. What sets is a solid reinforced wall.
-
Interlock — the blocks key together dry -
The core the concrete fills -
Pouring the wall -
One pour, top down -
Openings formed in the pour, not cut after -
Delivered stacked, built dry
03 — An annex
The same system, garden sized
A single-storey annex in a back garden, from poured shell to first fix.
-
Shell up, at the end of the garden -
Roof deck on -
Battened out, ready to clad -
Rooflight in, roof insulated -
First fix, before lining -
Cladding is your call — timber on a different job
Sizes
Three footprints.
28 m²
6.25 × 4.5 m
One bedroom, shower room, open-plan living and kitchen.
38.5 m²
7.0 × 5.5 m
More generous living space with a separate kitchen run.
48.75 m²
7.5 × 6.5 m
The largest footprint, with room for a second bedroom.
Before you start
An annex someone lives in needs planning permission.
Outbuildings can often go up under permitted development. A self-contained annex — its own bedroom, kitchen and bathroom — cannot. It needs full planning permission, building control sign-off, and it may change your council tax banding.
That is not a reason to walk away. It is a reason to get it right first. We supply the drawings and the technical pack your application needs.
Common questions
Annexe questions, answered straight.
Do I need planning permission for a garden annexe?
Almost certainly, yes. A garden room or home office can often go up under permitted development, but an annexe that someone lives in — with its own bedroom, kitchen and bathroom — is self-contained living accommodation, and that needs full planning permission plus building control sign-off. We supply the drawings and the technical pack your application needs.
Is it spelled annex or annexe?
Both are correct in the UK. "Annexe" is the more common British spelling for a building attached to or beside a house; "annex" is the American spelling and is also widely used here, particularly as a verb. They mean the same thing in this context, and we use them interchangeably.
Can I build an annexe in my garden for an elderly relative?
Yes, and it is the most common reason people come to us. This is often called a granny annexe or granny flat. It still requires full planning permission as self-contained accommodation, and some councils attach conditions tying occupancy to a family member or to the main house. Your planning officer will tell you which conditions apply locally.
Does a garden annexe affect council tax?
It can. A self-contained annexe may be banded separately for council tax. There is a statutory annexe discount in England for annexes used by a relative of the people living in the main house, and an exemption where the occupant is a dependent relative. Check the specifics with your local billing authority before you commit.
What are ground screws, and why is there no concrete slab?
Ground screws are steel piles wound into the ground with a hydraulic drive head. They take load immediately, so there is no excavation, no muck away and no waiting for a slab to cure before you can start building. They also sit lightly on the site, which matters if there are tree roots, services or a garden you would rather not dig up.
What is an ICF wall, and how is it different from a timber-framed garden room?
ICF stands for insulated concrete formwork. Insulated blocks are dry-stacked to form the shape of the wall, reinforced with steel, and then filled with concrete in a single pour. What you end up with is a solid reinforced concrete wall with insulation permanently on both faces. Doors and windows are hung in a poured wall rather than fixed to a panel, which is why it reads and behaves like a small house rather than a garden building.
How long does a garden annexe take to build?
We are not quoting a build time until we have completed-build data of our own to quote, and we would rather say that than invent a number. What we can say is where the time goes: there is no excavation and no slab cure before you start, the wall system goes up dry and is poured once, so the wet trades are few and short. The fit-out is yours and moves at whatever pace you set.
What do you supply, and what do I do myself?
We set out the site, drive the ground screws and level the steel ring beam — the engineering that is difficult to get right and expensive to get wrong. You take it from there: the block walls, the pour, the roof frame and deck, the membrane, and the windows and doors. Cladding, electrics, plumbing, heating, kitchen, bathroom and decoration are all specified by you.