First of all, cover the flooring and furniture around the fireplace with a dust sheet to guard against any sooty deposits.
Knock your knuckle in the area of the blocked fireplace. Does it sound hollow mostly all over? If so you probably have a hardboard cover mounted on a wooden frame. Carefully prise off the cover and remove the wooden battens. You will then need to carry out what is called a smoke test (see below).
However, if your knocking sounds solid all over the chimney breast, your fireplace has, almost certainly, been bricked up. Before going to the trouble of removing all the bricks, check that the chimney is working, again by carrying out a smoke test.
If the bricking up was done properly, there should be an air vent (ventilator) near the floor. Remove this. Then hold near the opening a taper (or a match) that has been lit then extinguished. If the smoke is drawn through into the chimney, the chimney is working fine. But if it isn't, be prepared for additional repair costs.
If your fireplace doesn't have an air vent, you will have to carefully cut out a couple of bricks a foot above the floor with a cold chisel and then carry out the smoke test described above.
Light my fire
Assuming you now have a working chimney you will then need to check on the following fireplace components (depending on what fuel and what type of fire you want):
1. Is there a decorative fire hearth visible or under flooring? Most types of fires need one - the only exception is some "hole in the wall" gas fires that are specifically approved for installation without hearths. For solid-fuel fires, any "stone" hearth should be in three sections to allow for expansion. Ideally, it should also have a metal hearth plate immediately in front of the fire itself.
2. For solid fuel, there should also be a sub-hearth made of concrete with its top at floor level.
3. If you want an open fire of the type used in UK houses for more than 100 years, make sure that there is a fire back in the fireplace. This protects the brickwork from heat and helps to radiate heat into the room.
* The Solid Fuel Association (SFA) publishes a leaflet called The Guide to Opening Up your Fireplace". Visit the website at (www.solidfuel.co.uk.
More fire facts
* Remember that London is a smoke-controlled area, and therefore you should not burn logs, only smokeless fuel (or gas).
* Some stoves, however, have been designed to burn wood in smokeless areas, and, accordingly, have an "exemption certificate". For more information on fuels and exempt appliances, see (www.uksmokecontrolareas.co.uk.
* And find a good explanation on which fires suit various types of traditional and modern flue at (www.valor.co.uk.
* Always check that a chimney is sound, and have it swept (find a sweep through (www.chimneyworks.co.uk).
* In showrooms, look for the logo of the National Fireplace Association (www.nfa.org.uk).
* Use a CORGI-registered installer for gas fires (http://www.trustcorgi.com); and a HETAS installer for solid fuel (http://www.hetas.co.uk).
* Be aware that an open fireplace (even when unlit) will adversely affect any future SAP energy rating and HIP.
* Fire efficiency is calculated by taking the amount of heat (in kW per hour) that a fuel might produce under ideal conditions, and dividing this by the actual output of the fire or stove. The result is given as a percentage figure.
* Open fires have a rating that, at worst, is less than 10 per cent, and, at best, 25 only per cent. For more advice/technical assistance, call 0845 643 1901.