Filling in holes in the chimney

[mrsnhp]

A previous owner has sealed a ventilation hatch in the chimney with a piece of lightweight concrete but hasn't mortared it all the way. After that, they've wallpapered the chimney and later built it in with chipboard, so it wasn't visible.

We've removed the chipboard and wallpaper and are planning to paint the chimney, but what do we do about the hole? What type of mortar should we use?

Currently, there's no fire in the chimney, but in the future, we might want to install a stove in the neighboring room and use one of the other flues if possible. Does that affect the choice of mortar?

 

[Claes Sörmland]

Then choose lime mortar that is easy to open later. Mix with a whisk and brick in a little brick or similar in the hole.

Regular C-bruk, which is easier to obtain, also works but it is a bit harder.

 

[mrsnhp]

Then choose lime mortar that is easy to open later. Mix with a whisk and set some bricks or similar in the hole.

Regular C-mortar, which is easier to obtain, also works but it's a bit harder.

We will not be firing in this particular flue, so I don't think we need to be able to reopen the hole unless we need to "redo" if something turns out to be done incorrectly.

I'm more wondering if you need something special for it to withstand potential heat. For example, we already have a sack of Finja "Laga vägg" and (of course) a bag of Husfix that we bought for something else, but nothing is said about chimneys on them, so maybe it's not suitable? Or does it not get that hot just because you're firing in another flue?

 

[Claes Sörmland]

Husfix is probably plastic if I remember correctly so it doesn't fit in chimneys.