Of all the reasons councils give for refusing a HMO, over-concentration is the one that feels most like being punished for other people’s HMOs. The council draws a circle around your property, counts the HMOs already inside it, and refuses yours because there are too many. You have designed a good scheme, you would run it well, and none of that matters, because the objection is not really about your house at all. It is a frustrating refusal, but whether it is worth appealing depends entirely on one thing: whether you are converting an ordinary house, or enlarging an HMO that already exists.
How the concentration rule works
Many councils set a threshold for how many HMOs they will tolerate in one place. Brighton and Hove, one of the busiest HMO appeal authorities in the country, refuses where more than 10% of homes within a 50-metre radius of your site are already HMOs. Other councils set the bar differently, 25% in Plymouth, 20% in Rhondda, and measure it over a different area.
Some also object to ‘sandwiching’, where a family home would be left with an HMO on both sides. The council typically keeps a database of known HMOs, drawn from planning, licensing and council-tax records, and counts them off against the threshold. Cross it, and you are refused. These thresholds usually sit alongside an Article 4 direction, which is what forces you to apply for permission in the first place.
When an appeal is close to hopeless
Be realistic. If you are converting a normal family house into an HMO, the council has a clear, up-to-date concentration policy, and the threshold genuinely is breached, an appeal will very probably fail. Inspectors back councils that have sound policies and apply them correctly. Fighting a concentration refusal on those facts, in the hope the inspector simply takes a different view of the same numbers, rarely works. Your energy is better spent elsewhere.
When it is genuinely arguable
The strongest case is where your house is already a lawful smaller HMO and you were refused permission to enlarge it to seven or more sharers. Several inspectors have decided that the concentration policy, aimed at protecting family housing, should not be applied where there is no longer a family house to protect. A second is where the numbers themselves are wrong, or the count is arguable: councils quite often miscount, or include properties they should not.
The most interesting cases depend on whether one extra person really changes anything. Because a small HMO becomes a large one at the seventh resident, adding a single tenant can require permission. In one Brighton appeal, at Whippingham Road, the inspector found that adding just one occupier made no real difference and allowed it. In another, at Hartington Road in the same city and the same quarter, on almost identical facts, a different inspector decided the extra person did unacceptably intensify HMO pressure and refused it.
That is the whole point: where the harm comes down to judgement, inspectors genuinely disagree, and a well-argued appeal that puts the right decisions in front of the inspector can tip a finely balanced case. In Cardiff, two appeals were allowed even though the area was over the council’s 20% limit, because so many properties nearby were already HMOs that one more changed nothing.
Appealing a concentration refusal
Under the appeal rules introduced in April 2026, the inspector decides on your application documents plus a short summary, with nothing added later. So if you are going to challenge the council’s count, or argue that your case is one of the arguable ones, the evidence has to be in the application from the start, and your 250-word summary has to make the point sharply. This is one piece of the wider picture we set out in our main guide to appealing an HMO refusal. For the full policy background, Martin Gaine’s book Planning for HMOs works through the concentration rules and the appeal decisions in detail.
If you have been refused because the council says there are too many HMOs nearby, send us the refusal and your drawings for free initial advice. We’ll check whether the concentration case is one of the arguable ones or a genuine dead end, and if it is worth appealing, we’ll prepare and manage it for a fixed fee of £399. More complex policy battles, and larger sui generis schemes, we can refer to our sister practice, Just Planning.