Denbighshire has more protected land than any county around it — the National Landscape, 32 conservation areas, a World Heritage Site buffer and a flood-prone coast. Whether your extension needs permission depends on where the house sits, what has already been built and what you want to do; it is not something you can tell from the street. Mike is in Hawarden, under an hour from all of Denbighshire, and checks all of it before you pay the £585 fee.
⚡ Get an instant estimate 📋 Book a £60 Initial Site Appraisal Meeting ⓘ Why an Initial Site Appraisal Meeting?Before anything else: four things decide whether your extension needs an application in this county, and a great many homes are caught by at least one of them without their owners knowing. Mike checks all four at the Initial Site Appraisal Meeting — only after those checks can anyone say whether permission is needed.
The Clwydian Range and Dee Valley covers much of the east and south of the county. Inside it, Permitted Development drops to single-storey only, no cladding or render, and side extensions are tightly limited. Two-storey work needs an application.
From Rhyl seafront to Ruthin's square. Same cut-back rights as the National Landscape, plus a case officer who will care about materials, roof pitch and what the extension looks like from the street.
The Pontcysyllte Aqueduct and Canal buffer zone follows the Dee valley through Llangollen and Llantysilio. The council asks for a short supporting statement with householder applications beside it. Mike writes it.
Parts of Rhyl, Prestatyn, Rhuddlan and St Asaph sit in flood zones. An extension does not need a locational justification, but the council can ask for a flood consequences assessment where the work might make things worse. Better to know on day one.
Building control in Denbighshire is the council's own in-house service. Mike submits the technical pack as a Full Plans application rather than a Building Notice, so any problem surfaces on paper before the builder is on site, not after. The council's building regulation charges are separate and based on floor area — the estimator below gives the range.
Denbighshire has more protected land than any of its neighbours. Roughly four-fifths of the Clwydian Range and Dee Valley National Landscape lies inside the county, the council lists 32 conservation areas, and the Pontcysyllte Aqueduct World Heritage Site buffer runs up the Dee valley to Llangollen. None of that stops you extending — but it means the rules are rarely as simple as the ones written for England, and the council's own planning staff will not tell you informally which apply to your address. Mike has drawn and submitted householder extensions across North Wales for 25 years and works Denbighshire every month. He'll tell you which side of the line you're on before you pay the council anything.
It depends — and in Denbighshire it depends on more things than most people expect. Welsh Permitted Development does allow some work without an application: a single-storey rear extension can go out up to four metres and up to four metres high, the same limit for any house type (one of the places English websites get Wales wrong). But that only holds if the house is outside the National Landscape and any conservation area, has not been extended before, is not listed, and the design stays inside every limit on height, width, position and materials. Two-storey extensions, side extensions near the front and anything on protected land normally need an application. You cannot tell from the street, and a tape measure alone will not tell you either. That is what the £60 Initial Site Appraisal Meeting is for: Mike checks the designations, the planning history and the proposal against the rules, and tells you which it is before any council fee is spent.
In the National Landscape and in a conservation area the rights are cut back: no extension of more than one storey, no cladding or render, and a side extension only if it is small and set well back from the front. A great many Denbighshire homes fall under those rules without their owners knowing — Llangollen, Corwen, Llandegla and Meliden are inside the National Landscape outright, and Ruthin, Prestatyn and Dyserth sit on its edge. If you have assumed you will not need permission, this is the county where that assumption most often turns out to be wrong.
If you do need it, the council fee is £585, plus the £149 Planning Portal charge — paid to them, not to Mike. Denbighshire works to the statutory eight weeks from the day it accepts the application as valid; allow longer once the survey and drawings are included, and longer again where conservation officers are consulted. Written pre-application advice is available from the council for £33 with a reply inside 21 days — useful on a borderline scheme, and Mike will say when it is worth the money. Mike prepares the drawings, submits them, and deals with the case officer. One fixed written fee. He does not build it.
The drawings follow Denbighshire's Supplementary Planning Guidance on residential development — the document the case officer judges your extension against. It expects a rear projection on or near a boundary of no more than three metres for a terrace and four for a semi or detached house, applies the 45-degree daylight test to neighbours' windows, keeps 21 metres between facing rear windows, and asks for a Green Infrastructure Statement with every application. Designing to it from the start is the difference between an eight-week approval and a round of amendments.
The whole of Denbighshire is the same council and the same page. On the coast: Rhyl, Prestatyn, Meliden, Dyserth and Rhuddlan. In the middle: St Asaph, Bodelwyddan, Trefnant and Henllan. Down the Vale of Clwyd: Denbigh, Ruthin, Llanrhaeadr and Llanbedr. Up the Dee valley: Llangollen, Corwen, Carrog, Cynwyd and Llandrillo. And the hill villages between — Llandegla, Llanarmon-yn-Iâl, Llanferres, Bodfari and Tremeirchion. The Denbighshire plans page shows how a typical job runs.
The town centres of Ruthin, Denbigh, Llangollen, St Asaph, Rhuddlan, Corwen, Prestatyn and Rhyl are conservation areas, as are many of the villages. Inside them, work that is automatic elsewhere may need an application. The boundary can split a street, so Mike checks the designation on the visit — it is never a surprise after the fee is paid.
Extension plans start from £750 and loft conversion plans from £950 — always as a fixed written fee, agreed before any work begins. The number you agree is the number you pay.
The £60 Initial Site Appraisal Meeting comes off that fee if you go ahead, so the visit effectively costs you nothing. Council and building control fees are separate throughout and paid directly. For the full picture on Welsh Permitted Development rules, see planning permission in Wales.
Once your fee is agreed, Mike returns and measures the house himself — no juniors, no outsourcing. This is the second visit; the earlier £60 Initial Site Appraisal Meeting comes off your fee.
Scaled drawings of your home as it is and as it will be — the documents your planning application stands on.
Prepared, submitted and handled for you — or confirmation you don't need one under Permitted Development, which saves you the council fee entirely.
The technical pack — structure, insulation, fire safety, drainage — that building control approves and your builder prices from.
Mike works to a fixed written fee, agreed before any work begins. Council fees are separate and paid directly — never through Mike.
| Item | Typical cost | Paid to |
|---|---|---|
| Mike’s fee — drawings & application handling | £750 – £1,800 by project | Mike (fixed, written) |
| Planning application (if required) | £585 Wales / £548 Cheshire | Your council |
| Planning Portal service charge | £149 | Planning Portal |
| Building control (approx.) | £450 – £2,000 by project | Council / inspector |
Or just use it right here ↓
Mike's fee plus the council fees for planning and building control — the full professional stage, before a builder is involved. Two taps for a figure — no obligation.
Mike’s fee covers the complete design and approvals stage:
Why the range? Every home is different. The lower end covers a straightforward project — standard drawings, no planning application needed. The higher end covers larger or more complex work — a full planning application, more detailed drawings, or structural design to coordinate.
Before any work begins, Mike gives you a detailed written fee proposal — so you know exactly what you are paying and what it covers. The number you agree is the number you pay.
Only if planning permission is needed. Wales charges £585 for a householder application and Cheshire West & Chester £548 — the fee is set nationally, so it does not vary between Welsh councils. Paid directly to your council, never through Mike.
The service charge for submitting a planning application online. It also only applies if permission is needed, and it is charged per application submitted.
This one always applies, permission or not. It is calculated on floor area and subject to the final design — smaller projects sit toward the lower figure, larger ones toward the higher. Paid to the council's building control team or a private approved inspector, never through Mike, and he gets you an exact quote once the design is finalised.
* Only payable if planning permission is needed. Mike determines that at the Initial Site Appraisal Meeting — before you commit to anything.
Design and approvals only. This is what it costs to get your project drawn and approved — it does not include your builder’s costs for the actual building work.
If your project turns out to be Permitted Development, the council planning fee and the Planning Portal charge do not apply at all — up to £734 you simply do not pay. Mike checks that for free at the Initial Site Appraisal Meeting.
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Guide figures only. The £60 Initial Site Appraisal Meeting is not added to these figures — it comes off Mike's fee when you commission the work. Council fees correct at July 2026; building control charges vary by council and project — full details in the FAQs. Mike confirms everything in a written fee proposal before any work begins.
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£60, and it comes off your fee when you go ahead. Mike comes to the property to understand the scope of what you want to do and advise you accordingly — then sends a written fixed fee afterwards.
Every planning application Deeside Architectural Design submits goes onto the council's public register — under the practice name, with the decision attached, permanently. It's free to search and it isn't curated by us. What the register cannot show you is the other half of the work: the projects that qualified as Permitted Development, needed no application at all, and saved the client the council fee. Those leave no public trace. So the number below is the part you can check — not the whole of it. Before you decide whether the fee above is worth paying, go and read it.
Submitted to Flintshire County Council under Deeside Architectural Design since 2010 — every one searchable, with its decision attached.
Many projects qualify as Permitted Development, need no application, and never reach the register. The 165 is the work that required permission — not the count of jobs done.
Deeside Architectural Design Limited, incorporated January 2010, and 25 years of drawings behind it. Companies House no. 07128221.
Open Flintshire's planning register, put Deeside Architectural in the Agent field, and read every decision — including the ones that didn't go our way.
Search Flintshire's planning register →
Figures taken from Flintshire County Council's public planning register, August 2026.
It depends on the house, not just the extension. Welsh rules, not English ones, allow some single-storey rear extensions without an application — but only outside the National Landscape and conservation areas, on a house that has not been extended before, and within strict limits. Denbighshire has more protected land than any neighbouring county, so the exceptions catch a lot of homes. The £60 Initial Site Appraisal Meeting is the check, before the £585 fee.
£585 to Denbighshire County Council if permission is needed, plus the £149 Planning Portal charge — paid to them. Written pre-application advice from the council is £33 if wanted. Mike's drawing fee is separate, fixed, and written down first. If it is Permitted Development, the council fee does not apply.
Eight weeks from the day Denbighshire accepts the application as valid. The survey and drawings sit in front of that, so allow around three months from first visit to decision — longer in a conservation area or the National Landscape, where more people are consulted.
The National Landscape takes in Llangollen, Corwen, Carrog, Glyndyfrdwy, Llandegla, Llanarmon-yn-Iâl, Llanferres, Bodfari, Tremeirchion, Meliden and Gwaenysgor, with Ruthin, Prestatyn and Dyserth close to its edge. Conservation areas include the centres of Ruthin, Denbigh, Llangollen, St Asaph, Rhuddlan, Corwen, Prestatyn and Rhyl and many villages. The line can split a street — Mike checks the exact address.
Not informally. Denbighshire says its planning staff cannot give informal advice on whether permission is needed; the formal route is a Lawful Development Certificate, with its own fee and wait. Mike's £60 visit answers the question first — measured, with the designations checked — before you spend anything with the council.
Mike Williams, BSc Architectural Design Technology, based in Hawarden and trading as Deeside Architectural Design Limited since January 2010, working across Denbighshire every month. Flintshire's public planning register lists 165 applications under the practice name — you can search it yourself above.
Two taps on the estimator gives you a realistic figure. When you're ready, the £60 Initial Site Appraisal Meeting comes off your fee if you go ahead.
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