The easiest course when refitting an old bathroom is to use equipment that is the same shape and size as the old equipment. Then all the pieces will fit in the same positions and the existing plumbing and waste runs can be used. But the opportunity of planning a new bathroom from scratch so that it works better than the old one is usually too good to miss.
Start by deciding what improvements could be made - for example, would a shower plus a bidet be a better idea than a bath? Should the WC be part of the bathroom, or separate from it? Would two wash basins ease the load on the bathroom in the mornings? Or should extra basins be put in some of the bedrooms?
Related you can read here: Sanitary Ware and Counter Top Wash Basin
There is an enormous range of bathroom equipment available. Some equipment is inexpensive and utilitarian; some is unashamedly luxurious; and some is designed to overcome special problems, such as a shortage of space.
Once you have decided what bathroom equipment you would like, cut out scaled-down plan shapes of the individual items from a piece of card and put these on a scale plan of the bathroom. Leave sufficient room around each piece of equipment so that it can be used properly - space for elbows at the side of the wash basin and for knees in front of the WC, for example. Add scale plans of these activity spaces to your cards. Where two fittings are unlikely to be used at the same time - for example, a WC and a bidet the activity spaces may overlap without making the bathroom any more awkward to use.
Do not forget to take account of things like windows and central heating radiators. Doors that get in the way could be rehung, or converted into sliding doors. Where possible, arrange equipment in a logical order - WC next to both basin and bidet, for example. Bear in mind that it is best to keep water and waste pipe runs short and that they may need to be concealed if they are not to look ugly. WC waste pipes are large and you may need to allow space for them.
Baths
Baths are made of a variety of materials. Enamelled cast iron, the traditional material, is very heavy (it takes two strong people to move a bath made of it), rigid and hard-wearing, but it has poor resistance to chipping and is expensive. Enamelled pressed steel has much the same properties, but is much lighter, a little less rigid, and relatively cheap. Plastic materials acrylic or glass reinforced plastics make a bath that is very light, fairly cheap, and with good resistance to chipping. But the bath needs properly supporting, has poor resistance to chemicals, and may melt if hot things like a cigarette end come into contact with it. The common shapes of bath are listed below.
Plain rectangular bath
Cheap; usually 700mm wide and 1700mm long, but other sizes are available.
Rectangular bath with extra features
More expensive than the simple type. Different brands have different features; handle grips usually for holding on to when moving about in the bath; nonslip base makes standing in the bath safer; dipped front makes it easier to climb in and out; taps need not be positioned at the end, but on one side, in a corner or plumbed into the wall; plug holes need not be at the end.
Corner bath
Usually has an oval bathing area. As well as looking different, it might be the answer to some space problems as it takes up less wallspace. Like other unusual baths, it is generally made of a plastic material - and may require a greater volume of water than a traditionally shaped bath.
Double-sized bath for comfort when bathing with a friend; many different shapes are available.
Bath with seat
A small, deep bath for sitting in rather than lying down in; some are deep enough to allow the water to come up to shoulder level.
Basins
Most basins are made of vitreous china which has good resistance to chemicals and naked (lames but is easily cracked or chipped. Other materials used include acrylic and enameled pressed steel.
Pedestal basin
The pedestal provides some support for the basin and helps to hide plumbing and waste traps. The basin is at a fixed height.
Wall-hung basin
Can be positioned at any height and leaves the floor clear, but relies completely on the wall for support and does not provide any cover for the plumbing and waste pipes.
Vanity or counter-top basin
The basin is mounted in a worktop or in a ready-made vanity unit with cupboards underneath. When cutting the hole for the basin, take the dimensions of the actual basin to be used, as these can vary in size by a few millimetres. The shop may cut the hole for you if you buy basin and vanity unit together.
Corner basin
Designed for use in confined spaces, but often a small wall-hung basin is a better solution.
Semi-recessed basin
Another solution to fitting a basin in a small area. Recesses about 60mm or so into the wall.