Plumbing for a Bathroom in a Loft

mixer taps

Loft conversions are a great way of adding bedrooms to a house. Looking up as you walk along many city streets of the Victorian and Edwardian eras you will notice a loft conversion on virtually every single property. With the increasing popularity of en suites it’s common to put a bathroom or shower room in a loft conversion too.

Adding a Bath or Shower

It’s not actually necessary to have a bathroom in the loft, just a toilet and a washbasin would be a great help. But of course fitting a bath or a shower in, to make it a proper en suite, will make it that more useful and add more value. The problems are, of course, with space.

A bath will take up a lot more floor space but at least the end of a bath can use areas where the headroom is restricted. You also have to be sure that you can actually get the bath up the stairs to the new en suite! A shower will take up less space but has to go where you have full height, in the centre unless you are extending the roofline out.

Extending and Plumbing

The key to making the plumbing simple for a loft conversion is to site the bathroom as a close as possible to the existing waste and supply pipes. This will make it easier, and therefore cheaper, to install the new en suite. Fortunately this is usually at the rear of the house, sometimes at the side.

If you are building the roofline out then you are unlikely to get planning permission to do it at the front, it will almost certainly have to go at the back. This will hopefully put the toilet and bath or shower in the right place to make connections to existing plumbing reasonably straightforward.

Dealing with Waste

This is particularly true of the waste pipe as it is wider, so it’s more difficult to get the pipe around corners. There needs to be a certain fall (gradient) along the length of the pipe too, to ensure that the waste flows out properly. You really need to avoid having to put in new waste pipe from the loft conversion if at all possible.

It’s not impossible but you then also have to excavate to link the new waste pipe into the correct drain. All of this adds expense. As the beauty of a loft conversion is that it adds maximum value to the property for the minimum outlay, extra expense should be avoided.

Using Micro-bore Pipes in a Loft Conversion

There is another solution to this problem though. Laying micro-bore plastic pipes from the new toilet to the existing waste is easier than with a traditional waste pipe. You need to add an electric macerator to the waste pip of the toilet; this grinds the waste down so that it is small enough to pass through the small-bore pipes. They often include a pump to push the waste out as well.

Take care with the plumbing layout though, as the plastic pipes don’t like 90 degree bends. Keep any bends to 135 degrees and you should be fine. This may need some lateral thinking to fit your layout but trunking and boxing-in can hide a multitude of sins.

Pushing Water up to a Loft Conversion

Getting water supplies up to the new en suite is a breeze after all the palaver with the waste. An electric shower with a pump will work well and there’ll be no messing about trying to fit a header tank into the restricted roof space left after the loft conversion is done. Mains pressure should be enough to push cold water to the toilet cistern and basin, the only thing you then have to resolve is hot water to the basin.

You might be lucky and find that there is enough residual pressure to drive water up to the loft from the hot tank, but it’s unlikely and you’ll probably need a plumber’s advice to find out first. You can install a small pump, which will be noisy, or an instant water heater over the basin, which will look naff.

If you have a combi boiler (which heats water instantaneously rather than heating a tank) you are more likely to have success getting hot water up to the basin without resorting to one of these undesirable solutions. These are designed to push hot water upstairs from a boiler in a kitchen or utility room so they may well go the extra mile.

Don’t Forget Ventilation

Regardless how you solve the plumbing problem, don’t forget ventilation. You may not be able to get a window in the bathroom area so an extractor fan is the best bet. This has the advantage that it will come on whenever the light is turned on, whereas you can’t always rely on people to open the window, particularly in winter.

See Also
walk-in shower
Does a Bathroom Need a Bath?
Plumbing a Bathroom Into an Extension

2 thoughts on “Plumbing for a Bathroom in a Loft”

  1. Without the expense of a whole loft conversion with a dormer how easy would it be to install a bedroom and en-suite for occasional guests.

    I have had a quote for 40k plus for a full loft conversion and installation for stairs but I don’t want to spend that kind of money for something I may need to use once or twice a year. I have an extended semi in Bexleyheath. Thanks

  2. we are buying a chalet bungalow, bathroom is downstairs we would like to put another bathroom upstairs in the 3rd small bedroom but it is at the front of the bungalow and the sewer pipe is at the back can it be done. It does have floorboards. If so what would the cost be roughly.

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