Closing up an unused flue

NSG666

Our house is late 60's built with a precast class 2 flue built into the inner skin of a cavity wall. The internal wall is flat i.e. no chimney breast. I've taken out the gas fire and now want to block up the hole which is c.85mm deep, 300mm wide and 600mm high. Have thought about timber battens and plasterboard but this may allow movement and cracking. Advice and suggestions please but leaving a vent at the bottom is not an option.

FreeBear

50x75mm stud frame to fit in the hole. Fixed firmly to the back/side, and it isn't going to move. Put a cross piece in half way up, and then screw a bit of 9.5mm plasterboard across the top. Some scrim tape (the mesh variety) between the PB and existing plaster, then plaster - The tape will help to stop any cracks appearing.

Venting a disused flue is nearly always a good idea - it only needs to be a small vent, not a huge great hole. Something like a uPVC trickle vent just above the skirting board. See how it goes without a vent, and add one if damp does become a problem.

NSG666

FreeBear said:

50x75mm stud frame to fit in the hole. Fixed firmly to the back/side, and it isn't going to move. Put a cross piece in half way up, and then screw a bit of 9.5mm plasterboard across the top. Some scrim tape (the mesh variety) between the PB and existing plaster, then plaster - The tape will help to stop any cracks appearing.

Venting a disused flue is nearly always a good idea - it only needs to be a small vent, not a huge great hole. Something like a uPVC trickle vent just above the skirting board. See how it goes without a vent, and add one if damp does become a problem.

Thanks FreeBear. I had missed a bit that I was also thinking about filling in the flue with flue vermiculite which I'd hope would reduce the chances of any potential damp issues to almost zero.

FreeBear

NSG666 said: I had missed a bit that I was also thinking about filling in the flue with flue vermiculite which I'd hope would reduce the chances of any potential damp issues to almost zero.

If you have access from the top, filling with vermiculite won't do any harm. Just put a decent cap on the top to stop rain from getting in.