Getting to Grips with the Promised Scale of Additional Housing supply from the Mayor’s Small Sites Initiative

Since the first day of the Examination in Public (on the inadequacies of the New London Plan’s impact analyses) LSE London representatives have challenged the fitness of a strategy relying exclusively on sustained intensification to deliver the required step change in housing deliveries.

Subsequent sessions of the EiP have worked back toward consideration of the underpinnings of the Plan’s optimistic housing targets. Christine Whitehead’s last blog (on day 10 of the hearings) summarised the first direct discussion of the credibility of this step change – including my expressed view that the targets were ‘sheer fantasy’. But though that day did cover discussion of one of the basic reasons for that judgement – namely the lack of evidence that the massive delivery gap (relative to assessed ‘capacity’) on large sites would be significantly reduced; that of the other – involving the quintupling of output from a category of (very) small sites, as a result of a new policy initiative – had to await the next day, dedicated to the ‘matter’ of small sites.

We didn’t actually participate in that session, so what follows relies on the audio recording provided on the GLA web-site.

The day was evidently a very full one, with extensive discussion from and/or about outer boroughs – where the expected impact of this initiative is very largely concentrated – addressing questions about both the credibility and acceptability of the intensification planned for the targeted category of sites. But this was preceded by a much broader discussion on the question of ‘modelling’ impacts on housing supply, on which this blog focuses.

Specifically, this involved an extended interaction between David Smith (as the panel member chairing this session) and members of the GLA team, seeking clarification as to how the SHLAA modelling of additions to ‘capacity’ (which in this case simply means output) was carried out. This culminated in acceptance by the team of the correctness of his summary that, in relation to the crucial ‘growth assumption’ (the proportion of eligible dwellings assumed to come forward each year) underpinning these estimates, this was:

 ‘‘partly a policy choice, partly based on judgement, and not based on any empirical study or anything like that” – EiP Recording [@1:58:16].

One of the factors involved in choosing a 1% value for the growth assumption was said to be:

‘the undesirability of having a too low a percentage rate – of say for example 0.5% — which would hinder London’s ability to meet its housing needs’ – EiP Recording [@1:57:57].

Though – since this is a matter of the assumptions deployed rather than of policy action – what would be affected is London’s apparent (rather than actual) ability to meet those needs. This is pretty much what we had guessed – not a reason for questioning the policy, but certainly one for scepticism about the likelihood of the assumed quintupling of this element of housing supply (in the next decade as compared with the period before).

The sensitivity test referred to in this context, which involved altering the growth assumption by 0.5%, with an estimated 95 thousand impact on housing delivery (over the decade presumably) underlines the point we have made elsewhere about the irrelevance of the headline shortfall of 10 thousand (over that period) to which many participants have referred in discussion of previous Matters.

Overall, listening to the discussion reinforced our view that the delivery assumptions in the Plan are reasonably described as sheer fantasy – and again a matter of assumption rather than evidence.