Water is becoming a planning constraint

Good evening!

Have You Considered Water Use as a Planning Constraint?

Half of England is now reported to be in an exceptionally serious drought following a very dry July. Water restrictions are already affecting a large share of the population, while reservoir levels and river flows have continued to fall. The Guardian reported the latest Environment Agency position on 29 July.

After receiving our latest water bill, I was surprised to see much water we actually use as a household daily, it wasn’t so much the cost but the volume. Our usage for two adults and a child is 215 litres per day which is good compared to the national average of 181 litres per adult, but it still made me cringe. So, in May I installed two water butts for the garden to harvest rainwater with the aim of using less drinking water for things like washing the car or watering the plants and vegetables. I was therefore feeling a bit pleased with myself when I was sitting on two full butts of water one week into the heatwave…but now even those have run dry.

A development appeared earlier this month in the government’s Water Demand Environment Act Target Delivery Plan.

The government intends to tighten the Building Regulations water-efficiency standard for new homes from 125 litres per person per day to 105 litres, with a target of 100 litres where there is a clear local need. It also plans to review drainage standards in Part H so that water reuse becomes easier to incorporate. The delivery plan was published on 16 July.

Consider Rainwater Harvesting

Rainwater harvesting and greywater reuse are often discussed as equipment choices but in practice, there are also drainage, storage and routing decisions that need to be considered too.

A tank may need space below the garden or inside the building as well as separate pipework required for toilet flushing or irrigation, maintenance access, overflow arrangements and controls which all need somewhere to go.

Adding those provisions after the foundations, drainage and landscaping are complete (i.e. retrofitting) is likely to cost far more than considering them during design.

The calculation can hide inside a fake specification

The easiest response to a tighter water-efficiency standard is therefore likely to lead people to select lower-flow taps, showers and toilets until the water calculation passes. Then once Building Regulations are satisfied and signed off, occupants will then likely replace the fittings for the ones they actually wanted, undoing the saving that appeared in the design-stage calculation. After all who wants a shower with an impressively low flow rate that feels disappointing to stand under or a bath that takes an hour to fill up?

I’ve seen this approach on stair hand rails, where a self-builder wants something that wouldn’t pass building regs so they install one that does and then remove it after the building has been signed off. This approach clearly creates more waste, rather than remove it.

The plot could be affected before the house

The second-order effect is on land.

In water-stressed areas, a local planning authority or water company may become more concerned about whether further development can be supported. A plot that looks suitable in policy terms can still face questions about supply capacity, drainage and the effect of additional demand.

For a prospective plot, check who supplies the water, whether the site has an existing connection, how far the main is from the proposed house and whether the local plan applies a tighter water standard. Where a borehole is being considered, the yield, treatment and permissions need investigating rather than assuming independence from the mains should also be considered.

This Week’s Biggest Self-Build News…

London consults on temporary CIL relief

16 July 2026

The government has opened a nine-week consultation on temporary Community Infrastructure Levy relief for qualifying residential developments in London. The consultation closes on 18 September. Read the government consultation.

This is an older item from the past fortnight, but it is worth mentioning because with margins tightening in developments CIL can determine whether a scheme remains viable. The proposal is aimed at larger London housing developments rather than individual self-build exemptions but its wider significance is that government is willing to alter infrastructure charges when they prevent viable homes from progressing.

Mortgage lending strengthened in June

29 July 2026

Bank of England data showed 58,200 mortgage approvals for house purchase in June, while net mortgage lending rose by £7.7 billion, the strongest monthly increase since March 2025. Reuters reported the figures on 29 July.

It suggests lenders are still willing to advance substantial sums despite higher borrowing costs.

The housing secretary questions the delivery target

25 July 2026

Housing Secretary Angela Rayner has acknowledged that delivering 1.5 million homes during this Parliament will be extremely difficult, pointing to construction costs and the wider delivery environment. The Times reported her comments.

The weakness in the national target is that it measures completed homes rather than accessible plots. A large development can improve the total without creating a single serviced self-build opportunity. The useful test for future housing announcements remains whether they release small sites, strengthen Right to Build delivery or require custom-build plots within larger schemes.

I hope this week’s stories help you spot where a small technical requirement can become a much larger project constraint.

Brendan