Check the chimney cowl

A chimney cowl sits at the top of the chimney and stops rain from entering, reduces downdraught, and keeps birds and debris out of the flue. They take a lot of weather and the fixings corrode, the mesh blocks with soot, and on older properties they can simply fail structurally.

If you have access to inspect it, check for blockages in the mesh, corrosion around the mounting, and whether the cowl is sitting straight. A partially blocked cowl will affect draw, particularly on a still day. A cowl that's come loose can end up inside the chimney, which is a more serious problem. If your stove has recently started drawing poorly on calm days, the cowl is the first thing to check.

Anti-downdraught cowls are worth considering if you're in an exposed location or have had persistent problems with smoke blowing back into the room. Various designs work better in different chimney positions and prevailing wind directions, so take advice if you're replacing one.