BNG de minimis exemption for self build in garden

[Fi and J]

Hello all 

 

I’m in pre-planning for a self build in the small garden of my modest ex council home in London. Garden is currently mostly 70s crazy paving with some overgrown odd bushes,  crushed by invasive ivy and a bit of mud where passers by throw rubbish (gardener’s world it is not). I’ll also need to demolish an old garage/old kitchen extension to create space to build new house on. 

Council planners (who are really supportive) suggested going for de minimis BNG exemption as they’ve never dealt with a self build exemption & so don’t have any protocol in place for monitoring to make sure it remains a self build. This forum suggests mortgage lenders may be spooked by 3 year legal agreement with LPA to live in the new house as it may preclude foreclosure (god forbid). 10% uplift sounds ferociously expensive even for my restricted site. 
 

questions : 

1. is a hedgerow different from a few bushes in a flower bed? 
2. Do the type of plants there now matter? Eg invasive ivy v native plant. 
3. is the 25m2 just a measurement of mud area, doesn’t really matter what’s growing in it? 
4. the site / deeds will be split for old (current) house and new build house, but planners want one application covering changes to old house (to ensure it meets current London minimum standards) and new house. The 25m2 de minimus should be for just the land that will be part of new house??   
5. householders are within their rights to trim all bushes on their land, we just haven’t bothered. Should we now ruthlessly tame all ivy/bushes etc? Is there any point? 
 

thank you for your time. This legislation does not help self builders enough. I do wonder if some of the self builders magazines etc should be lobbying the govt about such policy obstacles. 
 

thank you

 

 

 

 

 

[LnP]

There are several posts about this on here already. Google search Buildhub to find them.

 

We're demolishing an existing building and the new build will be mostly either over the existing foot print or over ground which is unvegitated. The area habitat which will be affected is currently lawn and less than 25 m² . We found an ecologist who wrote a report for us supporting a de minimis claim which we've included with our application. These judgements and answers to the questions you raised can be a bit subjective. Some ecologists are running BNG points banks and I can't help thinking they might be more inclined to support assessments where they can sell points, i.e. less interested in a de minimis claim. The ecologist we used wasn't doing that. He was recommended by our planning consultant. The report cost £200. We're keeping our fingers crossed the LA ecologist agrees.

 

I'm wondering how long it will be until somebody notices that BNG for self builders is unjust and a mess and does something about it.

[garrymartin]

2 hours ago, Fi and J said:

3 year legal agreement with LPA to live in the new house

Minor corrective point, but as I understand it, you aren't entering into a legal agreement to live in the house for three years. You're agreeing that should you not, you cease to be eligible for any of the exemptions for charges that you didn't have to pay for things like CIL and BNG, and any other associated things. I've seen on here that some mortgage lenders are spooked by that, but in the context explained, I can't understand why, to be honest.

 

 

[Great_scot_selfbuild]

3 hours ago, Fi and J said:

Hello all 

 

I’m in pre-planning for a self build in the small garden of my modest ex council home in London. Garden is currently mostly 70s crazy paving with some overgrown odd bushes,  crushed by invasive ivy and a bit of mud where passers by throw rubbish (gardener’s world it is not). I’ll also need to demolish an old garage/old kitchen extension to create space to build new house on. 

Council planners (who are really supportive) suggested going for de minimis BNG exemption as they’ve never dealt with a self build exemption & so don’t have any protocol in place for monitoring to make sure it remains a self build. This forum suggests mortgage lenders may be spooked by 3 year legal agreement with LPA to live in the new house as it may preclude foreclosure (god forbid). 10% uplift sounds ferociously expensive even for my restricted site. 
 

questions : 

1. is a hedgerow different from a few bushes in a flower bed? 
2. Do the type of plants there now matter? Eg invasive ivy v native plant. 
3. is the 25m2 just a measurement of mud area, doesn’t really matter what’s growing in it? 
4. the site / deeds will be split for old (current) house and new build house, but planners want one application covering changes to old house (to ensure it meets current London minimum standards) and new house. The 25m2 de minimus should be for just the land that will be part of new house??   
5. householders are within their rights to trim all bushes on their land, we just haven’t bothered. Should we now ruthlessly tame all ivy/bushes etc? Is there any point? 
 

thank you for your time. This legislation does not help self builders enough. I do wonder if some of the self builders magazines etc should be lobbying the govt about such policy obstacles. 
 

thank you

 

 

 

 

 

@Fi and J I feel your pain. I did a lot of research on this when we went through planning. There is legislation (statute law, so the council *must* follow it) stating that hey are to manage a register and process of tracking self-builds. They are required to report on it annually (you can put in an FOI to request the stats - I did), so that is no reason for them to avoid what may well be an easier exemption criteria for you. Here are some relevant links and policies that helped me:

 

(Useful but you may need to check if anything has been updated since it was published)

 

Self-build statute legislation (get familiar with this, get yourself on the council’s self-build part 1 register too):

https://www.legislation.gov.uk/ukpga/2015/17/section/2/2016-10-31

 

Key Legislation and Policy Sources

1.

Environment Act 2021

• This is the primary legislation introducing mandatory Biodiversity Net Gain (BNG) in England.
• It amends the Town and Country Planning Act 1990 to require a 10% BNG for most new developments.

📌 BUT: The Act itself doesn’t list the exemptions — it gives the Secretary of State the power to create exemptions via secondary legislation.

 

2.

The Biodiversity Gain (Exemptions) Regulations 2024

✅ This statutory instrument (SI 2024 No. 3) provides the legal basis for the self-build and de minimis exemptions.

 

 

🔍 Key self-build exemption section:

• Regulation 4(1)(d) – Exempts self-build and custom housebuilding where:
  • The site is less than 1 hectare,
  • No more than 9 dwellings are proposed,
  • It is not part of a larger development.

 

📖 You can find this SI here:

https://www.legislation.gov.uk/uksi/2024/3/contents/made

 

3.

BNG Planning Practice Guidance (PPG)

– Updated 2024

• This is the official government guidance that supports the law and helps LPAs and developers interpret the rules.
• It details how to claim a self-build exemption, what counts as custom housebuilding, and what evidence is required.

📚 Available on the GOV.UK site:

https://www.gov.uk/guidance/biodiversity-net-gain

Look under:

• “Exemptions from biodiversity net gain”
• “Small sites and self-build developments”

 

4.

Self-build and Custom Housebuilding Act 2015 (as amended)

• Defines what qualifies as self-build or custom housebuilding.
• You must meet this definition to claim the exemption under BNG regulations.

 

✅ Summary of Requirements for the Self-Build BNG Exemption:

 

According to the Biodiversity Gain (Exemptions) Regulations 2024, you must show that:

1. You’re building a home that qualifies as self-build or custom,
2. The development is fewer than 10 dwellings on less than 1 hectare,
3. It’s not part of a phased or larger scheme.

Good luck!

[LnP]

2 hours ago, garrymartin said:

Minor corrective point, but as I understand it, you aren't entering into a legal agreement to live in the house for three years. You're agreeing that should you not, you cease to be eligible for any of the exemptions for charges that you didn't have to pay for things like CIL and BNG, and any other associated things. I've seen on here that some mortgage lenders are spooked by that, but in the context explained, I can't understand why, to be honest.

 

 

This is not correct in my experience. Where did you get this? Is there an LA doing it like this? Don't mean to sound rude, just curious.

 

In my LA, and the Dorset one which was posted elsewhere on BH,  when you sign the UU, you are entering into a covenant that you will be the first occupier and that you will not sell the house for 3 years from the date of your first occupation. This is enforced by the deed, i.e. the UU, being a local land charge and registered as such by the Council - you can't sell your house until either the LA remove the charge or it expires. Obviously this is a problem for lenders as if the owner defaults on the loan, they can't dispose of the house to recover their money.

 

None of this is required by the regulations. It's regulatory over reach by the LAs.

[Oz07]

@LnP do you think if you stripped a plot bare before applying for pp you could argue an increase in biodiversity?

[LnP]

1 hour ago, Oz07 said:

@LnP do you think if you stripped a plot bare before applying for pp you could argue an increase in biodiversity?

No. The way it works is that you have to start by working out the "pre-development diversity value". If you've done work on the land since 30th January 2020, you have to go back to the diversity value before you did the work. It's in  The Environment Act Schedule 14, Part 1, paragraph 6.

 

I can imagine though that in some circumstances it might be difficult for the LA to establish how the land was, but you can expect them to look e.g. at historical Google Earth images.

 

 

[DevilDamo]

7 hours ago, LnP said:

This is not correct in my experience. Where did you get this? Is there an LA doing it like this? Don't mean to sound rude, just curious.

The CIL paperwork itself a charge on the property/site. Some LA’s may ask applicants to enter into a separate legal agreement, but definitely not all. 

[Fi and J]

Hi all 

 

yes that’s a good point that I’d be entering a legal agreement with LPA not to sell the new house rather than to live in it. I’m planning to live in it unless death / serious illness etc gets in the way. I agree it’s over reach by LA’s but im getting used to the system not being entirely sensible or fair. I will rely on mortgage to build so it’s a key issue . 
 

what I can’t see covered in other posts here is garden builds and whether 25m2 de minimis is confined to the part of the plot which will be the new house or 25m2 includes new house area + old house area. Any clarity on this would be extremely helpful. 

[LnP]

7 hours ago, DevilDamo said:

The CIL paperwork itself a charge on the property/site. Some LA’s may ask applicants to enter into a separate legal agreement, but definitely not all. 

I'm no expert, but my understanding .... CIL and BNG are completely different obligations, but the link is that they are both enforced by the LA under section 106 of the 1990 Town & Country Planning Act. And the BNG UU explicitly states, "This Deed is a local land charge and shall be registered as such by the Council". And there's no CIL where I am.

[LnP]

4 hours ago, Fi and J said:

Hi all 

 

yes that’s a good point that I’d be entering a legal agreement with LPA not to sell the new house rather than to live in it. I’m planning to live in it unless death / serious illness etc gets in the way. I agree it’s over reach by LA’s but im getting used to the system not being entirely sensible or fair. I will rely on mortgage to build so it’s a key issue . 
 

what I can’t see covered in other posts here is garden builds and whether 25m2 de minimis is confined to the part of the plot which will be the new house or 25m2 includes new house area + old house area. Any clarity on this would be extremely helpful. 

So you're splitting off a building plot from the garden of an existing house and leaving the existing house. The question is simply whether the area habitat which will be lost when you build the new house will be less than 25 m² . Crazy paving is not habitat and neither is unvegitated land, but the overgrown bushes might be. If you're going to make a de minimis claim, I think your LA is probably going to want that to be supported by a report from a competent ecologist. I suggest either getting a recommendation from an independent planning consultant or phoning round a few and discussing you case with them. If you're a bit marginal on the <25 m² , you might get a feel for whether a bit of bush clearance might help.