How to open up an old fireplace

In most cases, a fireplace and grate will be blocked off using sound-building practices, but in some homes, this may not be the case. It’s always advisable to get expert advice from a surveyor or architect before you begin work.

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Credit: hikesterson

Before you start: This is likely to be a messy job, so fold back the carpet or lay down lots of dustsheets to protect your furnishings.

If the chimney has been blocked up correctly, there will be a vent in the wall just above the skirting board. Remove this vent and use a torch to look inside the opening. This will give you some idea of the size of the fireplace opening.

Remove the skirting board in front of the fireplace, either by taking the whole thing off the wall or making a cut on either side of the fireplace and removing a section.

This is the solid section of floor in front of the chimney breast. It is usually a concrete slab set into the surrounding floorboards. 

A hollow sound indicates that the fireplace was probably blocked up with a board. If you can find the edge, which sometimes shows up as a bump under the wallpaper or paint, cut around this with a trimming knife and try to pry out the board with a wrecking bar. 

If this is difficult, drill a hole in the board to see whether it is plasterboard or timber. Break out a plasterboard sheet, using a club hammer, or use a padsaw or jigsaw to cut around the edge of a timber board. Unscrew or lever off any supporting battens.

If the fireplace has been filled in with bricks, start from the vent and slowly knock out a few at a time with a club hammer and bolster chisel. You may find it easier to remove the plaster from the area first and then chip out the bricks, one by one, once you can see where the mortar joints are. Work left and right and upwards, gradually opening up the hole.

Cut the bricks back to the edge of the original opening before making good any joints in the brickwork at the side and back of the fireplace. Use a lime mortar specially formulated for fireplaces; you can buy this in small bags from fireplace suppliers. Regular sand and cement mortar will crack with the heat.

Once the fireplace is revealed, you will be able to see whether the original fireback is still in place and in good condition. The fireback is a shaped section, often made from iron or fireclay, at the back of the fireplace. It is designed to reflect heat from the fire into the room, rather than allowing it to rise straight up the chimney.

A cracked fireback can be repaired with fire cement. Brush the area clean and spray the cracks with water to wet them, then fill them with cement. Let the cement dry for three days before using the fireplace.

8. Check the draught

Check the draught of the chimney by holding a lighted candle just in front of the fire opening. Smoke and flame should be drawn up the chimney. If not, the chimney may well be blocked or capped off. Remove blocking within the flue. Get professional help if the flue has been capped at the top.

9. Chimney sweep

Get the chimney swept before installing a new grate or fireback. A professional sweep will be able to advise on the condition of the flue and will remove any build-up of soot and tar from the inside of the chimney. Contact the National Association of Chimney Sweeps (NACS) for a list of registered professionals in your area.

10. Checking the flue

Fires give off toxic fumes, which can kill. In a well-designed and correctly working fireplace, these are exhausted up the chimney and pose no threat to occupants of the house. 

Get a professional to examine your chimney before you light a fire for the first time, whether you have opened up an old fireplace or installed a new one. Find a qualified chimney engineer in your area by contacting the National Association of Chimney Engineers (NACE).

Read more: How to renovate and install antique fireplaces

Read more: How to wallpaper around radiators and fireplaces

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