Can a prefab storage room replace a home extension?
Contents
In short
- A prefab storage room makes sense for serious storage that does not need to connect to the house, and that you may want to move.
- An extension suits space that is part of the house, but you must think about settlement and permits.
- Leave room around it to open the door, move things and repair walls, with at least 0.50 m on unused sides.
- Check distances from the boundary and any estate rules before ordering.
Prefab room or extension?
| Topic | Prefab storage room | Home extension |
|---|---|---|
| Time on site | Short, because it is made in a factory | Longer, with structural and concrete work |
| Link to the house | Separate. You walk outside. | Reached from inside the house |
| Effect on the house | No need to fix it to the house | Needs a designed joint and separate footings |
| Moving it | Usually possible | Not possible |
| Appearance | Choose one that suits the house | Easier to match the house |
| Paperwork | Ask locally, based on its use | Ask locally, and check estate rules |
When a prefab room is better value
- For storage, garden equipment, tools or stock, and not a room people live in
- When you have space on the land but do not want to disturb the house structure
- When you need it quickly
- On rented land, or if you may move later
- When the house is on soft ground, where an extension risks uneven settlement
When an extension fits better
If you use the space from inside the house every day, such as a back kitchen or laundry room, an extension is more convenient. But extensions often settle differently from the house, which usually stands on deeper piles. So keep the new structure separate, do not cantilever beams from the house, and allow for a joint that can move. Have an engineer or an experienced builder check the design.
How much space to leave around it
The space around the room is a matter of both use and law. The figures below are what we suggest for use, and you should adjust them to the real thing. Where a side faces the boundary, also check the legal distances in the next paragraph.
| Side | Suggested space | Why |
|---|---|---|
| In front of the door | At least 1.00 m | To open the door and carry things in and out |
| Unused sides | At least 0.50 m | To reach the wall for repairs and clear leaves |
| Side facing the house | 0.60 m or more | To keep airflow and avoid standing water |
| Roof water | Along the gutter line | So water does not fall on the house or a neighbour |
On the legal side, Ministerial Regulation No. 55 (2000), clause 50, covers buildings up to 9 m high. Walls with doors, windows, vents or light openings must be at least 2 m from the boundary. A wall closer than that must be solid and at least 0.50 m away. To build right on the boundary, the wall must be solid and you need the neighbouring owner's written consent. Local rules can differ, so ask an official. See Do you need a permit to place a knock-down house on your land?
In a housing estate, check the management's rules as well, because back gardens may have extra limits.
Matching the room to what you store
- Damp: keep the floor off the ground and use open shelves so things do not go mouldy.
- Air: include vents, especially for things with a smell.
- Security: choose a strong lock and avoid windows that show valuables.
- Dangerous goods: do not keep fuel or chemicals in a closed room with everyday things.
- Power: allow for one light and a socket for tools.
It needs stable supports too. See Preparing your site: ground, supports and truck access.
Frequently asked questions
Can it go right against the fence?
Check the boundary distances in the law and local rules. Even where it is allowed, a small gap makes wall repairs and rainwater easier to deal with.
Can it be a temporary bedroom?
Not if it was made for storage, because it may lack the insulation and ventilation people need. If someone will stay in it, choose a room designed for living in.
Does it need supports?
Yes. Placed directly on soil, it can tilt and get damp. Supports keep it level and away from ground moisture.