Can you join several units into a bigger house?
Contents
In short
- Yes. Two 3×6 m units make 6×6 m, and three make 6×9 m.
- The three risk points are the roof joint, the supports and any wall you open up.
- Designing and making them as one set is easier than joining units from different batches.
- Before opening a wall between units, have the manufacturer or an engineer confirm it.
What size do you get?
Placing 3×6 m units side by side along the long edge adds 3 m of width each time, while the length stays the same.
| Units | Outside area | Example use |
|---|---|---|
| 2 units (6×6 m) | 36 m² | 2 bedrooms, or 1 bedroom and a living room |
| 3 units (6×9 m) | 54 m² | 2 bedrooms, living room, kitchen and bathroom |
The usable area is smaller, because these figures include every unit's walls. If the walls between units cannot be opened, you end up with long rooms side by side and have to plan a way into each.
Think about the roof joint first
Leaks usually come from the gap between units, where two roofs meet. The common options are a joint cover with a waterproof seal, or a single roof over all the units, which cuts the number of joints to look after.
- Ask which way rain runs off the roof, and make sure it does not run towards the joint.
- Route gutters and downpipes away from walkways and supports.
- Sealant ages, so check it every year before the rainy season.
- Plan a safe way up to clean the joint.
Plan the supports as one set
All units must sit at the same level. If one sinks more than another, the joint opens, doors between units stick and the roof leaks. Ask the seller to set out the support points for all units together, and have your builder check the levels as a whole, not unit by unit. See Preparing your site for how to check levels.
Can you open the wall between units?
It depends on how that model is built. In some models the walls work with the frame to carry loads, and cutting one could make the house sag or open the joints. Before you order, ask:
- Which walls can be opened, and how wide?
- Where do extra columns or beams go?
- Is this done at the factory or on site?
- Does the warranty still apply afterwards?
If the answers are unclear, ask a structural engineer.
Power, water and placing order
- Power: decide on one panel or several, and how cables cross the joint.
- Water: keep the bathroom and kitchen close together so pipe runs are shorter.
- Placing order: if the crane can only reach from one side, place the furthest unit first.
- Precise placing: ask the crew to keep the gap shown on the drawing and not force units together.
- Permits: a larger total area is a reason to ask about permits. See Do you need a permit to place a knock-down house on your land?
Several units or one large house?
Several units suit building in stages, or land that large vehicles cannot reach, because each unit is easy to deliver. One large house assembled on site suits a continuous open space with no roof joints. Ask for prices for both at the same area and compare them.
Frequently asked questions
Can I join units from different brands?
We do not recommend it. Heights, column positions and roof systems may not match, which makes the joint difficult. If you must, have a builder measure them on site first.
Can I buy one now and add more later?
Yes, if you allow for the land, truck access and supports, and plan which wall will be joined. Tell the seller from the start.
Can units be stacked into two storeys?
Only models designed for stacking. The lower unit must carry the upper one, and a safe stair is needed. Never stack single-storey units without a designer's approval.