🏠 Buying & Renovating
Adding an Extra Bathroom: What It Involves and What It Costs
A second bathroom is one of the most requested upgrades. Where you put it decides most of the cost.
Marcus Ibe · Sep 25, 2026 · 6 min read · 4 steps
An extra bathroom or shower room can make a busy household run more smoothly and is often attractive to buyers. But the cost varies enormously depending on one thing in particular: how far the new room is from the existing drains.
Planning around plumbing is the difference between a straightforward job and an expensive one.
Location is everything
Waste pipes need a steady fall to drain properly, and toilets need a large-diameter connection to the soil stack. A bathroom directly above or next to an existing one is the cheapest option. Putting one on the opposite side of the house may mean long pipe runs, lifting floors, or a macerator pump.
Common places to find space
- A large bedroom split to create an en suite
- Under the stairs for a downstairs toilet
- A box room or large landing cupboard
- A loft conversion, if headroom allows
- A utility room that shares a wall with the kitchen
The things people forget
- Ventilation: an extractor fan ducted outside is required in most places
- Hot water: a combi boiler or cylinder may struggle with two showers at once
- Electrics: bathroom zones have strict rules on what can go where
- Permissions: building regulations or permits usually apply to new drainage
Budgeting
Get at least three quotes and make sure each one covers the same scope: plumbing, electrics, tiling, fixtures, and making good. Fixtures range from budget to luxury, so choose them before you compare prices. Add a contingency of at least 10 to 15 percent for surprises once the floor comes up.
This is general home-maintenance information, not professional advice. Building codes, permits, and safe practices vary by location — consult a licensed contractor, electrician, or plumber for work beyond your experience.