Frequently Asked Questions
The questions we are actually asked.
Straight answers on planning, listed buildings, cost and programme — including the ones where the honest answer is that it depends.
Planning & consents
- Do I need planning permission for an extension?
- Often not. Many single-storey rear extensions fall under Permitted Development, which lets you build without a full planning application — but there are limits on depth, height, materials and how much of the garden you cover, and they are stricter on semi-detached and terraced houses. Permitted Development rights are also removed entirely on some properties, including most flats, listed buildings and homes in conservation areas subject to an Article 4 direction. We establish which applies to your property at survey stage, before any design work, because it changes what is worth drawing.
- What is listed building consent, and do I need it?
- Listed building consent is separate from planning permission and is required for any work that affects the character of a listed building — inside as well as out. It applies to far more than people expect: removing a partition, changing a floor finish, replacing a window, even altering a fireplace can require it. Carrying out work without consent is a criminal offence, and enforcement can require you to undo it at your own cost. If your property is listed, assume consent is needed and let us confirm rather than the other way round.
- How long does planning take?
- A householder planning application is determined in eight weeks in principle. In practice, expect longer — validation delays, consultation periods and requests for further information all add time, and listed building or conservation area applications typically take longer still. This is the stage of a project we control least, which is why we start it as early as the design allows.
- We are in a conservation area. What changes?
- Conservation area status does not stop you altering your home, but it does mean the council will take a view on how the work looks from the public realm. Materials, window design, roof form and boundary treatments come under closer scrutiny, and some Permitted Development rights may be withdrawn. In our experience applications succeed when the design is clearly sympathetic from the outset — arguing with a conservation officer after submission rarely works.
Cost & programme
- What will my project cost?
- We cannot give a meaningful figure without seeing the property. The cost of an extension is driven by the structure, the ground conditions, how much of the existing house is affected and the level of specification — and those vary enormously between two houses on the same street. What we can do is give you an honest early view after a first conversation, so you know whether the project you are imagining is in the right region before anyone spends money on drawings.
- Why is a detailed quotation better than a rough price?
- Because a rough price is a guess that both sides later argue about. We quote against an agreed design and a written specification, itemised so you can see what is included and what is not. If something is excluded, it says so. A quotation you do not understand is not a quotation, and you should ask about anything on ours that is unclear.
- How long will the work take?
- A single-storey extension is typically a few months on site; a whole-house renovation runs considerably longer, and phased projects can span years. We give you a programme before we start. The honest caveat is that older buildings hide things — rotten joists, failed drainage, inadequate foundations — and finding them changes the programme. We would rather tell you that at the start than surprise you in week six.
- Will the work add value to my home?
- Often, but not always, and not by a fixed percentage. On two projects where the owners have shared independent valuations, the uplift was 50% and 37% respectively. Those are specific properties with specific figures, and part of any increase reflects the wider market rather than the work alone. Anyone quoting you a guaranteed percentage return on building work is guessing.
How we work
- What does design and build actually mean?
- Most projects involve three separate businesses — an architect, a structural engineer and a builder — with you coordinating between them and absorbing the cost when something falls between the gaps. We coordinate architecture, structural engineering and construction through one Mansouri-managed team, under one contract and one point of contact. The practical difference is that design and delivery answer to the same people, so the finished room matches the drawing and there is nobody to pass blame to.
- Who will I be dealing with day to day?
- One point of contact throughout. You will not be re-explaining your project to a different person each week, and you will not be chasing a subcontractor you have never met.
- Do you work on listed and period properties?
- Yes — it is a substantial part of what we do. We work with lime mortar, handmade and reclaimed brick, knapped flint, green oak framing, natural slate and clay tile, and we have taken listed building consent applications through to completion. Heritage work is a specialism rather than an extension of general building: the materials behave differently, the regulatory framework is different, and the consequences of getting it wrong are often irreversible.
- Are you insured?
- Yes. £10M employers liability, £3M public liability and £1M professional indemnity. Certificates are available on request and we would encourage you to ask any contractor for theirs.
- What happens after the work is finished?
- We walk the finished work with you and list anything that is not right before we consider the job closed — this is the moment to be critical. After completion we remain contactable. Buildings settle and occasionally something needs attention; we would rather you called us than lived with it.
Living through the work
- Can we stay in the house?
- Usually for an extension, often not for a whole-house renovation where services are being replaced. We will tell you honestly which applies to your project at quotation stage rather than after you have committed, because it affects your costs as much as ours.
- What do you need from us during the build?
- Decisions, promptly. Most delays on a site are caused by waiting on a choice rather than waiting on the work. If you are away or hard to reach for a period, tell us in advance and we will get the relevant decisions made before you go.
If your question is not here, ask us directly. We would rather have the conversation than have you guess — and we will tell you if your project is not one for us.
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We carry £10M Employers Liability · £3M Public Liability · £1M Professional Indemnity