HomeExtensions
House Extensions in Hertfordshire
Extensions are the bulk of what we do. Over a hundred of them in the last two years, from single-storey rears to full wrap-arounds, built by our own team from the first dig to the last coat.
More room, without moving house
With moving home not always an option, it may be wise to extend your property. There are many different types of extensions on offer from rear kitchen extensions, side returns and double storey extensions. Our experienced management team are able to visit your home, measure up and propose the most suitable design for your property that will meet local planning permission or permitted development requirements.
We tell you what is possible before you spend anything
Let Holman Simmons visit you completely free of charge to assess what additional space your house could benefit from. We offer impartial, expert advice letting you know what is possible with or without planning permission and fully explain the processes. We will then provide an extension plan ready to take the next step.
The roof is ours too
Every extension we build gets its own roof structure, cut on site or trussed, flat or pitched, with the roof lights set in before it is covered. Because we build the structure underneath rather than inheriting it from another trade, there is nobody to blame if it leaks and nobody to chase to come back.
One team, so there is nobody to chase
Groundwork, brickwork, carpentry, roofing and plastering are all done in-house. The steels, the drainage and the making good are ours too. You deal with the same people from the survey to the snagging, and the person who quotes your job is the person running the site.
Rear, side return, wrap-around or double-storey
A rear extension is the common one, taking the back of the house out into the garden, usually to open up the kitchen. A side return fills in the narrow strip down the side of a terrace or semi, which is often dead space. A wrap-around does both at once and changes the ground floor completely. A double-storey takes a bedroom out over the top of whichever of those you build. Which one suits your house is the first thing we work out on the visit, and it is free.
A finished room, or just the shell
Most people want the whole thing done: kitchen in, floor down, decorated and ready to live in. Some would rather we build the structure and make it watertight, then fit it out themselves or bring in their own kitchen company. We do both. The extension we finished in Bishop's Stortford in February 2026 was a shell-only build. Whichever you choose, the written quote says exactly where our work stops, so nobody is guessing at handover.
Where we build them
Hertford is home and more of our work is there than anywhere else, but we build extensions across the county: Ware, Bishop's Stortford, Hoddesdon, Buntingford, Welwyn Garden City, St Albans and Stevenage, and the villages around all of them. Each town has its own page with the jobs we have done there or nearby and the council that handles planning, because the national rules are the same but the authority applying them changes from one district to the next. If your town is not listed, ask anyway. Scott is happy to travel.
What decides the price of an extension
We do not publish a price list, because two extensions of the same size can end up thousands of pounds apart. The difference nearly always comes from one of these, and we look at every one of them on the visit:
- What is under the ground, which decides how deep the footings have to go
- How much of the back wall comes out, and how many steels carry the house afterwards
- Drains under the new footprint that need diverting, or a manhole that needs rebuilding
- The glazing: bifolds, sliders and roof lights vary more in price than anything else
- Whether you want a watertight shell or a finished room with the kitchen in
What is included
- Free site visit and honest advice on planning permission
- Written quote covering the work and the materials
- Footings, over-site and drainage
- Structural steels, working to your engineer's calculations
- Brickwork, blockwork and the roof structure
- Plastering, second fix and making good
- Building Control liaison throughout
- Site cleared, and we come back for anything that needs it
Recent extension projects in Hertfordshire
Real jobs from our own team, with the town and the month they went up on our Instagram. Where a post did not name the town, neither do we.
Common questions
Do I need drawings for an extension?
Yes. Professional drawings will be required as part of the planning phase. We are happy to provide help and guidance with this.
Do I always need planning permission for an extension?
It is not always necessary. Many extensions fall under permitted development rights, which set limits on how far out and how high you can go. We assess whether permission is required during your initial free consultation, before you spend anything on drawings.
How long does it take to build a house extension?
Every project is different. From our initial consultation we will be able to give you a good estimate of the time frame involved, and it goes in the written quote rather than being left vague.
How much does a house extension cost?
The honest answer is that it depends on the size, the ground conditions, how much structural work is needed and the finish you want. We will not guess a figure over the phone. The visit, the advice and the written quote are all free.
Do you build extensions in my town?
We are based in Hertford and work across the county from there: Ware, Bishop's Stortford, Hoddesdon, Buntingford, Welwyn Garden City, St Albans and Stevenage, plus the villages around them. If you are somewhere not on the list it is still worth asking. Scott is happy to travel, and the visit and the written quote are free either way.
Is a garage extension the same as a garage conversion?
No, and people use the words for both. A conversion turns the garage you already have into a room, which is the cheaper of the two. An extension builds new space, sometimes over or alongside the garage. If you are not sure which one you want, that is a normal place to start and we will work it out on the visit.
Do you build two-storey extensions?
Yes. One of our Google reviews is from a customer whose two-storey rear extension we built, and in February 2026 we had a side double-storey extension underway in Hertford. A second storey is more likely to need a full planning application than a single-storey extension, so it is one of the first things we check on the visit.
Can you build just the shell and let me finish it?
Yes. We finished a shell-only extension in Bishop's Stortford in February 2026. We build the footings, walls, steels and roof and make it watertight, and you take it from there. The written quote sets out exactly where our work stops.
Do you deal with Building Control?
Yes, all the way through. Building Control inspect an extension at set stages, from the footings to the finished job, and we deal with them at each one so you are not left chasing inspections. One customer picked out our relationship with Building Control in their Google review.
Want a proper price for it?
Tell us roughly what you are planning and Scott will come and look. The visit, the advice and the written quote are all free.
Worth reading before you ask anyone for a price:
