If you’re converting your loft space to create additional bedroom accommodation, it makes sense to incorporate en suite bathroom facilities on the same floor for convenience. If the loft conversion is to be a new master bedroom, an en suite bathroom should be seen as essential, and will likely improve the value of your home.

An en suite bathroom need not take up much space, but it is important to make sure that the space allocated has sufficient headroom for features such as the WC, basin and shower to function comfortably.

Planning a loft en suite layout

Start your en suite project with a scale floorplan of the loft space and mark a dotted line showing where the ceiling height reduces down to 1.8m, 1.6m and 1.4m. This will enable you to plan where the bed and other furniture can go while leaving sufficient full-height space for you to move around and it will show the space left to create the bathroom.

Putting in a dormer window can create extra headroom, but if this is not possible, a rooflight can still add 150mm — which can make all the difference over a WC or basin.

  • The bathroom will typically be formed using timber studwork, clad in marine ply and tile backing board (inside) and plasterboard (outside), with the voids filled with acoustic insulation.
  • Metal frames are available to build into stud walls for a wall-mounted WC with a concealed cistern, or a wall-mounted basin.
  • The voids between the studs are ideal for concealing the plumbing, soil pipes, wiring, concealed cistern and mixers for taps and showers
  • You may even be able to use voids in stud walls for forming storage niches.

A shower room will fit into a space measuring only 1m by 2.6m, with a WC, basin and a 900mm square shower tray — full headroom is required here, but the ceiling can start to slope down over the WC cistern. A bathroom will need at least 1.7m by 2.3m floor area to incorporate a WC, basin and standard bath. The ceiling height can be reduced over one end of the bath or the side of the bath, and behind the cistern, so it is sometimes easier to fit a bath into a loft room than a shower.

En suite lighting and ventilation

It is not essential to have a window in a bathroom, but if it is possible it is desirable. Planning permission isn’t usually an obstacle for a small dormer window or gable window, providing you use obscured glass and no part of the window opens below 1.7m. Ventilation is essential to meet the Building Regulations, so an extractor fan will be needed to provide both background and rapid extract ventilation.

Planning the plumbing

You should mark on your floorplan where any existing soil pipes for bathrooms on lower floors are located, as it will be easier to connect the new en suite to one of these than to put in a new soil pipe. Although this may also be possible, depending on the location of the drains outside — look for the inspection chambers or talk to a plumber.

Connecting water and drainage

  • If you can’t connect into a soil pipe, you can still create a bathroom anywhere in the loft and connect it using flexible small bore waste pipes and a pumped unit with a macerator.
  • Hot and cold plumbing can be branched off from an existing bathroom on the floor below, and the pipes hidden in a service duct, or in the back of a cupboard. Flexible plastic plumbing can make retrofitting far easier than rigid copper pipe.
  • If your plumbing works from a header tank, this will need to be moved higher than the loft bathroom taps or showerhead to create pressure.
  • It is possible to use a flush shower tray, or walk-in shower tray in a loft bathroom, but the floor level may need to be built up to accommodate the waste trap.
  • For a walk-in shower, it is best to use a pre-formed tray with an integrated trap and to tank the whole floor, dressed up the walls by 100mm, so that the water can only escape down the trap.

You may need to fit a mains pressure plumbing system, with either a combi boiler providing instant hot water on demand, or a boiler and unvented cylinder. A mains pressure system requires at least 1 bar of pressure — enough to lift water 10m. If the local mains pressure isn’t adequate, water could be pumped from a coffin tank to create the necessary pressure.

Heating

A radiator towel rail is usually sufficient to heat a small bathroom, but it is nice to have underfloor heating too, especially if your floor is tiled. Electric underfloor heating mats are inexpensive (around £100 for 6m²) and will only raise the floor level by 3-4mm, so they can be laid beneath tiles.

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