What actually sets the price
Distance to the soil stack. A WC sitting within a couple of metres of an existing stack is straightforward. Push it further and you are either running a graded waste under a floor or fitting a macerator, and both change the job.
Floor construction. A suspended timber floor can usually be lifted and notched. A solid concrete slab means chasing or a raised plinth, which adds labour and affects the finished floor height.
Ventilation. An internal cloakroom with no window needs mechanical extraction, wired and vented properly. Our own electrician does that, so it does not sit waiting on another trade.
Whether the space already exists. Reusing an understairs cupboard is cheaper than forming a new stud partition, door opening and lighting circuit.
Where a downstairs WC can realistically go
Understairs voids work when there is 1.1m of usable headroom over the pan and a door that can open outward without blocking the hall.
Utility room corners are often the easiest win, because water, waste and power are already there.
Converting part of a hallway is possible but you lose circulation space, so we usually mark it out on the floor at survey stage before anyone commits.
A cloakroom must not open directly into a kitchen without a lobby or compliant ventilation arrangement, which is worth knowing before you plan around it.
Keeping a small job from turning into a big one
Get the drainage route confirmed in writing. It is the single line that decides whether this is a two-day job or a week.
Choose a compact pan and a wall-hung or semi-recessed basin early. Swapping to a full pedestal basin later can cost you the door swing.
Ask for the quote to price strip-out, waste routing, extraction, electrics and making good as separate lines. Ours do, and they include VAT.
Frequently asked questions
Is a downstairs toilet cheaper than a bathroom?
Usually yes, because there is no bath, no shower and much less tiling. But if the WC needs new drainage or a macerator, the gap narrows quickly.
Do I need a macerator?
Only when gravity drainage cannot be achieved. We always try for a graded gravity waste first, because it is quieter, has nothing to fail and does not need servicing.
Does adding a downstairs loo need building regulations?
The drainage, ventilation and electrical work are all covered by the regulations, so the work has to comply and be certified. We handle the notification and hand over the paperwork.
How long does a cloakroom take?
Two to four working days for a straightforward conversion. Add a couple of days if a new partition, door or drainage run is involved.
Do you do the plumbing and electrics yourselves?
Yes. Plumbing, electrics and tiling are all done by our own team, so nothing on site waits for a subcontractor to turn up.