Dry storage/washing room extension

[Jozsef Nagy]

Hi all,

I am planning a small DIY infill extension/lean-to style structure at the rear/side of my house and would appreciate advice before I go too far with the design.

The area is shown in the attached photos. The proposed build would fill in the existing paved area between the house/kitchen door side and the existing garage/outbuilding area, which is about 2400mm x 2700mm.

My current idea is:

• Concrete foundation/base.
• 3 courses of engineering brick above ground level with proper DPC.
• Timber-frame insulated structure or brick qall above.
• Suspended timber floor with insulation and proper ventilation.
• The existing kitchen external door would remain in place.
• The existing garage/outbuilding door would also remain in place and stay lockable.
• The new area would not be heated.
• I am not planning to open it into the house or remove the existing external doors.
• It would be used as a separate unheated utility/storage type space, not habitable accommodation.

The neighbour’s wall/structure is currently approximately 350 mm from the garage/outbuilding, and the new structure would keep the same gap. I do not intend to build onto the neighbour’s wall or rely on it structurally.

My main question is about the legal/compliance route for mainly the foundation and if that is confirmed, then the structure.

Because the proposed foundation would be very close to the neighbour’s wall/structure, I assume the Party Wall Act may be relevant, especially if any excavation goes deeper than the neighbour’s foundations. I want to do this properly and avoid undermining or affecting their wall.

Questions:

1. Would this likely be treated as a normal house extension for Building Regulations, even though it is unheated and separated from the house by the existing external door?
2. Is there any realistic way this type of build could be treated as exempt from Building Regulations, or is that unlikely because it is insulated timber-frame rather than a conservatory/porch?
3. For the foundation, what would be the safest and most compliant DIY-friendly approach this close to a neighbouring wall: shallow raft/slab, trench fill, pad foundations, ground screws, or something else?
4. If I use a shallow foundation solution that does not go below the neighbour’s foundation level, would that usually avoid triggering Party Wall excavation notice requirements, or is notice still likely because of the distance?
5. Would Building Control normally want to inspect this type of foundation even if the existing house and garage doors remain in place?
6. Are there any key details I should design in from the beginning: DPC height, DPM connection, suspended floor ventilation, fire resistance near the boundary, drainage, guttering/overhangs, or access gap to the neighbour’s wall?

I am happy to keep everything within my boundary and do it properly. I am mainly trying to understand whether this can be designed lawfully under permitted development / exemption rules, or whether I should assume Building Control approval and possibly Party Wall notice will be needed.

Any advice from people who have dealt with similar narrow side/rear infill extensions would be much appreciated.

[Jozsef Nagy]

Sorry, the current distance is 475mm, not 350.