It is quite possible to lay your own carpet. Start by measuring the dimensions of the room. Draw a plan on a sheet of paper â€“ it does not need to be to scale but your measurements need to be accurately made a recorded. Mark on the plan, as well as the length of each wall, the position of door ways and any other features where the carpet will need adjustment. From this plan, work out how much carpeting you need, both in terms of square metres and in terms of the required length and breadth. Remember that the carpet has to be cut into the doorways and you need to allow a few inches extra for this. Ideally, you do not want to have any joins or seams. This should be possible since carpets are now made in a wide variety of standard sizes, and it should be possible to buy carpeting that allows you to have very little waste indeed.
There are two decisions to be made before you begin (this is apart from the obvious decision of choosing a carpet that won't make you feel ill every time you enter the room!). You need to decide whether or not to lay an underlay. Underlay will not only preserve the life of the carpet, it will also help with insulation. Even with foam and rubber backed carpets, where the underlay is meant to be built in, it is worth considering laying a separate underlay.
You also need to consider how you are going to fix the carpet down. If it is not fixed to the floor, it will, undoubtedly, start to creep, and you will have to constantly pull it back into position. To fix it down, you can use double-sided tape, provided there is no underlay, or carpet tacks, or gripper strips â€“ these are strips of plywood with sharp copper tacks. They should be glued to a concrete floor and nailed down to a wooden floor. They're vicious things to use and are really intended for a woven carpet, not a rubber-backed one, but they are probably the most effective fixing!
Make sure that the floor is clean and relatively smooth. If you are using underlay, lay it first, joining the bits together with carpet tape and fixing the underlay to the floor with double sided tape. Leave a gap, of an inch or two, all round the room to allow you to fix down the carpet.
Place the roll of carpet along one wall, Wall A, and start to unroll it. Make sure the edge is firmly against the wall and fix that edge it down along the floor, either with double-sided tape or with gripper strips. Use a wooden mallet or rubber headed hammer to tap the carpet down along the wall. (There is a specialised tool, called a carpeter's knee-kicker for doing this, if you want a really professional finish; they can be hired.)
Unroll the carpet to the opposite wall, Wall B, and fix it down loosely, either on a gripper strip or with a couple of bits of tape. Don't press it down â€“ this is a temporary fixing. Stretch the carpet, working from the centre to the corners of Wall B. Fix it down at Wall B, without yet cutting off any excess. Cut a triangular notch in the excess at each corner so that the carpet will lie flat. Now, from the centre, stretch outwards to each of the other 2 walls, walls C and D, and fix the carpet down along both of these walls. Your triangular notches, cut from each corner, will allow the carpet to lie flat, with the excess rising up the walls. With a bolster chisel, press the carpet into the angle of the floor and wall (easier if there is a skirting board to press it into) and then, with a stanley knife, cut off the excess carpet, remembering to leave enough to fit into the doorways.
At the doorways, use your bolster chisel to crease the carpet round the door frame, cut off the excess and screw down a threshold bar over the carpet's edge.
You will need to vacuum clean the carpet immediately in order to pick up loose bits of fluff from the cutting process. This also helps to bed the carpet down.