You're right to highlight mansarding - it's a good policy and yes the increase in bedrooms seen in South Tottenham is a good sign that thinking beyond new homes can improve results.
Where we disagree are the phrasing "extreme affordable housing demands" - sends us down a potential political rabbit hole of debating what's more extreme, the lack of affordable housing, or requiring some. Though of course there's a balance to be struck.
Allowing mansard bedrooms and more side and rear extensions will turn suburban streets into building sites with skips, tradesmens lorries, parking chaos, etc etc as happened when basement extensions were allowed in places like Clapham in London.
Doesn't affect me personally, but it was hell for neighbours for months or years.
There's still an awful lot of if/but discretion here. It would be simpler and provide pinpoint certainty if development such as adding another storey or two, or building houses in an existing residential area did not need any pp. Why do I need pp to build a house next to a house?
On the national level. there should be...
1/Automatic approval for all sites included in the local plan. Why bother to go thru the process of creating a plan if it can just be ignored and development refused.
2/Removal of the local authority monopoly power to decide which land is acceptable for development. LAs sould not be permitted to refuse pp for land that is not included in the plan.
3/Reduction in green belt-designated land. We cannot provide sufficient houses in places like Surrey and Herts when some LAs are 90% gb. The gb was created by memo, without mandate and it can be removed in the same way. Gerrymandering our urban fringes to stop Lab voters moving into Tory constituencies was wrong then and, I would suggest, ripe for a HRA legal challenge now.
3a/ The govt should be explicit with the public that there is no guarantee that gb size and boundaries are permanent and that gbs may be changed to accommodate national objectives.
One of the very few areas in Greater London that exceeded home-building targets over the last decade was the Purley and Coulsdon area at the southern edge of Croydon borough. The great majority of this came from developers buying up bungalows and other low-density single-family homes, then converting them into buildings with 6-9 apartments. I imagine you know of this case, but so many of these small developments have been done that, in aggregate, they have added a lot of housing to the area. These units were typically a mix of 1,2 and 3 bedroom apartments, increasing housing stock of smallers units to an areas where smaller living spaces are rare.
One can also imagine that this caused a lot of objections locally, but the council policy adhered to broader housing policy and it did allow a whole lot of building.
However, when the politics of the council leadership (and new elected mayor) changed a few years back, they expressly flipped to a policy of default objection to any such building, so virtually nothing of that nature has been built since.
This wasn't even greenfield building, it was building (almost all of it in walking distance to a train station) on existing sites and increasing density.
I hope we can see more of this, given that London sorely needs more housing.
One other one in the area to look up is that Taylor Wimpey is now looking to build c300 homes on Chipstead golf course, very much short walking distance to Chipstead station. Between the golf course and the station there are already quite a number of apartment buildings that fit that economic need of affordable property close to a station. However above the golf course is an eye-wateringly expensive housing area, Chipstead village. The reactions have been predictable. Micro vs Macro as is understandable.
They should be reflected in the land prices paid and can provide early scheme cashflow.
A much more serious threat is the inherent tendency of the private speculative model to dribble out supply accordant with a perfectly rational commercial desire to maintain local pricing and profit margins as per Letwin report.
The question of viability also hinges on assumptions applied. In short, can depend on who is doing the developing.
Probably the correct phrasing is that AHOs can potentially reduce developer profits in some situations depending on business model applied and wider external market and public policy circumstances. .
The "dribble out" you refer to doesn't actually change how many homes get built each year. It changes the timing on particular sites, but makes no difference to the overall amount.
It's a total red herring when discussing quantity of housing.
Separately, it's massively overestimated in importance. It only applies to a fraction of locations, only for owner-occupied, and it doesn't even delay the median house on a given site very much
Faster build out rates should increase housing supply over the short to medium term.
I agree, however, that for the overall quantity, as well as affordability, of housing to increase at a sustained and significant level, wider system changes are required, consistent with faster build-out of large sites but much else besides.
Planning reform is necessary but not sufficient. For an annual sustained 300,000 new supply level, between 100,000-140,000 need to be publicly enabled and the business models of developers incentivised to shift towards profit from volume rather than margin.
You're right to highlight mansarding - it's a good policy and yes the increase in bedrooms seen in South Tottenham is a good sign that thinking beyond new homes can improve results.
When I was at the London Assembly, we supported airspace development in our Midrise report ' published back in March. https://www.london.gov.uk/who-we-are/what-london-assembly-does/london-assembly-work/london-assembly-publications/between-skyscrapers-and-semis-londons-missing-mid-rise-housing
Where we disagree are the phrasing "extreme affordable housing demands" - sends us down a potential political rabbit hole of debating what's more extreme, the lack of affordable housing, or requiring some. Though of course there's a balance to be struck.
Allowing mansard bedrooms and more side and rear extensions will turn suburban streets into building sites with skips, tradesmens lorries, parking chaos, etc etc as happened when basement extensions were allowed in places like Clapham in London.
Doesn't affect me personally, but it was hell for neighbours for months or years.
There's still an awful lot of if/but discretion here. It would be simpler and provide pinpoint certainty if development such as adding another storey or two, or building houses in an existing residential area did not need any pp. Why do I need pp to build a house next to a house?
On the national level. there should be...
1/Automatic approval for all sites included in the local plan. Why bother to go thru the process of creating a plan if it can just be ignored and development refused.
2/Removal of the local authority monopoly power to decide which land is acceptable for development. LAs sould not be permitted to refuse pp for land that is not included in the plan.
3/Reduction in green belt-designated land. We cannot provide sufficient houses in places like Surrey and Herts when some LAs are 90% gb. The gb was created by memo, without mandate and it can be removed in the same way. Gerrymandering our urban fringes to stop Lab voters moving into Tory constituencies was wrong then and, I would suggest, ripe for a HRA legal challenge now.
3a/ The govt should be explicit with the public that there is no guarantee that gb size and boundaries are permanent and that gbs may be changed to accommodate national objectives.
One of the very few areas in Greater London that exceeded home-building targets over the last decade was the Purley and Coulsdon area at the southern edge of Croydon borough. The great majority of this came from developers buying up bungalows and other low-density single-family homes, then converting them into buildings with 6-9 apartments. I imagine you know of this case, but so many of these small developments have been done that, in aggregate, they have added a lot of housing to the area. These units were typically a mix of 1,2 and 3 bedroom apartments, increasing housing stock of smallers units to an areas where smaller living spaces are rare.
One can also imagine that this caused a lot of objections locally, but the council policy adhered to broader housing policy and it did allow a whole lot of building.
However, when the politics of the council leadership (and new elected mayor) changed a few years back, they expressly flipped to a policy of default objection to any such building, so virtually nothing of that nature has been built since.
This wasn't even greenfield building, it was building (almost all of it in walking distance to a train station) on existing sites and increasing density.
I hope we can see more of this, given that London sorely needs more housing.
One other one in the area to look up is that Taylor Wimpey is now looking to build c300 homes on Chipstead golf course, very much short walking distance to Chipstead station. Between the golf course and the station there are already quite a number of apartment buildings that fit that economic need of affordable property close to a station. However above the golf course is an eye-wateringly expensive housing area, Chipstead village. The reactions have been predictable. Micro vs Macro as is understandable.
For train station area development,
the French model of coordinated development zones (ZACs) is worth looking at
https://thefrenchbuild.substack.com/p/inside-the-zac
Affordable housing planning requirements don't and won't 'wipe out' developer profits.
They should be reflected in the land prices paid and can provide early scheme cashflow.
A much more serious threat is the inherent tendency of the private speculative model to dribble out supply accordant with a perfectly rational commercial desire to maintain local pricing and profit margins as per Letwin report.
The evidence suggests that high affordable requirements do in fact cut developer profits and make some schemes unviable.
https://cayimby.org/blog/california-cities-wanted-free-affordable-housing-turns-out-theres-a-huge-cost/
Thanks, Sam.
OK, they can cut developer profits below a desired set maximal level but can support the business models of others through cash flow support: see: https://www.linkedin.com/pulse/market-system-adjustment-tale-two-developers-vistry-berkeley-newton-xzdye/
The question of viability also hinges on assumptions applied. In short, can depend on who is doing the developing.
Probably the correct phrasing is that AHOs can potentially reduce developer profits in some situations depending on business model applied and wider external market and public policy circumstances. .
The "dribble out" you refer to doesn't actually change how many homes get built each year. It changes the timing on particular sites, but makes no difference to the overall amount.
It's a total red herring when discussing quantity of housing.
Separately, it's massively overestimated in importance. It only applies to a fraction of locations, only for owner-occupied, and it doesn't even delay the median house on a given site very much
Faster build out rates should increase housing supply over the short to medium term.
I agree, however, that for the overall quantity, as well as affordability, of housing to increase at a sustained and significant level, wider system changes are required, consistent with faster build-out of large sites but much else besides.
Planning reform is necessary but not sufficient. For an annual sustained 300,000 new supply level, between 100,000-140,000 need to be publicly enabled and the business models of developers incentivised to shift towards profit from volume rather than margin.