Yes, and the most useful one comes from three checks rather than from a second designer's taste. Will your council validate the set as drawn? Does the scheme sit within the borough's own design guidance? And what will the neighbours see from their windows? You can run the first two yourself in an evening with two free documents from your council's website. For a view that actually carries weight, ask the council through pre-application advice; our pre-application request is £245, and the council's own pre-app fee is paid to them.
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We should be clear about what we do not sell: there is no stand-alone "drawing review" on our price list. What we offer is below, with its price.
What should a second opinion actually check?
Three questions, in this order, because each one costs more to fix later than the one before.
Will it be validated? A set that fails validation does not start the eight-week clock. It costs little to fix before submitting and weeks to discover afterwards.
Does it fit the local guidance? Most London boroughs publish a householder design guide with numbers in it: rear extension depths, eaves heights, dormer set-backs. Officers start from those numbers.
What does it do to the neighbours? Loss of light, outlook and privacy to the houses either side is a frequent reason officers and neighbours object to householder schemes, and it is the one a designer working from your side of the fence can underrate.
How do I check the drawings against the validation list?
Find your council's local validation list; search the council's name with "local validation list". A local requirement only counts for validity if it is on a list published on the council's website less than two years before you apply (MHCLG, Making an application, paragraph 039), so check the date on the front.
Then hold the drawings against it. Haringey's August 2024 list is a good example of how specific London lists are: every application needs a scale bar, proposed plans and elevations need at least one significant dimension so officers can measure them with software, drawings must carry a number and revision note, and floor plans must show the neighbouring property at the same level or 5 metres beyond the boundary, whichever is less (Haringey Local Validation List).
Things to look for on your own set:
- Does every sheet have a scale bar and a stated scale, and no "do not scale" note?
- Do the plans, elevations and sections agree with each other on window positions and heights?
- Is the existing shown as well as the proposed, so the change is clear?
- Are the neighbours drawn where the list asks for them?
- Is the red line on the location plan around the whole site, to the road?
If something is missing, add it before you submit. Our post on what planning drawings include lists the national requirements every set must meet.
How do I check the design against the borough's guidance?
Find the borough's householder or residential extensions guidance, usually a supplementary planning document. Then measure.
Brent's guidance, adopted in January 2025, is a useful model of what to measure. For terraced and semi-detached homes a two-storey rear extension must not be more than 3 metres deep from the original rear wall, and must not cross a 45 degree line taken from the middle of the nearest habitable room window on the neighbour's original rear wall (Brent Residential Extensions and Alterations SPD). A single-storey rear extension up to 3 metres deep on an attached home could be up to 4 metres high if the eaves stay at 3 metres or less, the guidance says.
Two things trip people up here. "Original rear wall" means the house as first built, so an earlier extension may already have used the allowance. And the 45 degree line is drawn on plan from a neighbour's window your drawings may not even show. If the scheme sits outside the guidance, it is not automatically refused, but your drawings and statement need to say why it is acceptable.
How do I judge the impact on the neighbours?
Stand in your garden and look back at the houses either side. Note which rear windows are kitchens, living rooms or bedrooms, and how close they are to the boundary. Then check the drawings: is the new wall height at the boundary given, and does the roof slope away from the neighbour or towards them? Is a new side window looking straight into next door? Would a balcony on the flat roof overlook a garden?
A designer can answer all of these on the drawings with a dimension or a section through the boundary. If yours do not, that is the gap a second opinion should name.
Who can give a second opinion that counts?
Anyone can give an opinion. Only the council's officers decide. National guidance says pre-application engagement can improve the quality of applications and their likelihood of success, and that councils may charge for it at no more than the cost of the service (MHCLG, Before submitting an application). Fees and response times vary by borough; our pre-application advice cost post sets out what to expect.
Here is what we can do, at published prices:
- A constraints report at from £19: whether the address is in a conservation area, under an Article 4 direction, listed or in a flood zone. Many second-opinion problems are really a missed designation.
- A pre-application request at £245: sketch proposals, the council's form and submission, and a plain reading of the officer's response, credited against our planning service if you go ahead.
- New proposed drawings at £395, where the scheme needs redrawing rather than tweaking. We only work over another firm's drawings once you confirm you are free to use them.
Frequently asked questions
Will you look over my drawings for free? We do not offer a free or paid stand-alone review. If you send drawings with a quote request, we tell you which of our priced services fits, and why.
Is the council's pre-application advice binding? No. It is the officer's view at the time, and the decision is made on the application. It is still the most reliable indication you can get before submitting.
My designer says the 45 degree rule does not apply to single-storey extensions. Is that right? It depends on the borough. Brent's 45 degree test is written for two-storey rear extensions; other boroughs apply a version to single storeys. Read your own council's guidance.
Can a second opinion guarantee approval? No one can. A second opinion reduces avoidable risk: invalid sets, numbers outside the guidance and neighbour impacts nobody drew.
