Living on site while you build: mobile home, caravan or cabin

Many people ask the same thing: could we buy a mobile home or cabin, put it on the plot, and live there while the house goes up? It would save rent and keep you close to the build. It is also one of the easier ways to start a planning problem, so find out what your council will accept before you spend money on a unit.

Do you need planning permission?

Development needs permission unless it is exempt. Development includes a material change in the use of land, and using a field as someone’s home is a different use from farming or storing things on it. The Act does not list caravans as a special case you can park anywhere. So if you plan to sleep in the unit, work on the basis that you need permission, and ask the council to confirm it.

A few points that people often get wrong:

• Owning the land is not enough. The right to own a site is not the right to live on it.
• A garden cabin used as a room is different. Small outbuildings used as storage or a hobby room can be exempt within limits. Once someone lives in it, that stops being true.
• “Temporary” is not a planning category by itself. A unit that stays for a year or three is a use of the land, and the council decides whether it is acceptable.
• A rear-garden home is not the same. The Class 3A exemption allows a qualifying detached house behind your own home. It excludes caravans and mobile homes, and it is no use on a bare site.

If you are unsure, you can ask the council for a declaration under section 5 of the Act on whether something is development or exempt. It takes time, so ask before you buy.

Asking for temporary permission during the build

Some councils will grant permission for a caravan or mobile home on site for a limited period while an approved house is built, with a condition to remove it once the house is finished. It is more likely to be accepted when:

• the house already has permission, or you apply for both together;
• the unit stands close to the building site and not in the open countryside on its own;
• the period matches a realistic build programme, with a little spare time; and
• wastewater and water have an acceptable arrangement.

Ask the planner what the county development plan says and what they usually grant. A pre-planning meeting is the quickest way to find out. The planning conditions guide explains how to read a removal or occupancy condition, and the planning permission guide covers the main application.

What living on site really costs

Before you commit, list every cost that belongs to the unit and not to the house. The purchase price is only the first line.

• The unit itself, which you may be able to sell on afterwards, usually for less than you paid.
• Delivery, a level base and removal at the end. Ask the supplier for the cost of taking it away.
• The planning application, a site layout drawing and any specialist reports the council asks for.
• A temporary electricity connection and a water supply, each applied for separately.
• Wastewater: a holding tank, its emptying by a licensed collector, or a small treatment unit.
• Heating and running costs, which can be high in a poorly insulated unit through a winter.
• Insurance for a unit that is lived in, and for its contents.

Add these up for the whole build, which for a one-off house is often longer than people plan for. Compare the total with renting nearby for the same months, as in the last question above. Some people find renting cheaper and simpler; others value being on the site daily, which helps with deliveries, security and decisions as work goes on. Either is a fair choice. What matters is that you made it with the whole cost in front of you.

Alternatives to a unit on the plot

If the council says no, or the sums do not work, there are other routes:

• Rent nearby and visit the site. This avoids the planning and wastewater questions.
• Stay in an existing house on the land, such as a family home, while you build. That is already a lawful use.
• Build in phases so that part of the house is habitable early, with the council’s agreement on the sequence. Your certifier must be comfortable with an occupied part of an unfinished building.
• A small permanent building first, if the permission allows it, such as a garage you will later convert. Check with the planner before you assume this is possible, because a conversion is also a change of use.

Wastewater and services

Wherever you sleep, the council and the Environmental Protection Agency expect wastewater to be treated. A unit with a toilet or a shower on a site without a sewer needs a lawful route for that water.

• A holding tank emptied by a licensed collector is the simplest temporary answer in many cases. Ask the council whether it will accept it.
• Do not drain a temporary unit to a field or a ditch. That is pollution, and it can be reported by a neighbour or found at an inspection.
• Keep the unit off the percolation area. The ground for your permanent system must stay undisturbed. The wastewater guide and the site assessment guide explain why.
• Water and power need arrangements too. A temporary electricity connection and a water supply are separate applications, and they take time.

Insurance for the unit and the site

Caravan and mobile home policies are often written for holiday or part-time use. A unit you live in full time, on a building site, with a self-build going up next to it, may not be what the policy was written for. Tell the insurer:

• that you will live in it, for how long and why;
• where it will stand, and who owns the land; and
• that building work is going on beside it.

Ask whether your contents, liability and fire cover continue, and whether the self-build policy needs to mention the unit. The self-build insurance guide shows the covers you need for the works.

The risk of building first and asking later

Many people decide to place the unit first and apply afterwards. It is a real risk:

• The council can send a warning letter, and then an enforcement notice if the matter is not resolved.
• Ignoring a notice can end in a court order to remove the unit and a prosecution.
• Retention permission may be available, but a grant is not guaranteed, and applying does not pause enforcement. See the retention guide.
• A lender, a solicitor or a buyer may later ask about unauthorised development on the site. It can delay the mortgage drawdowns or a sale.

Questions to ask before you buy a unit

• The council has confirmed in writing whether living on site needs permission, and what it will allow.
• The house has permission, or you are applying for both together.
• You have a lawful wastewater arrangement and a place for it.
• Electricity and water connections are arranged.
• The insurer knows you will live there, and has confirmed cover.
• You know what you will do with the unit once the house is done, and what it costs to move.
• Your lender knows about it, if you have a self-build mortgage.