Filling deep holes in brickwork before lime plastering

[reejoc]

Hi all,

About to embark on lime plastering the back of an inglenook fireplace. The plan was to point up using lime mortar prior to plastering.

Old soft brick and after stripping off some cement render there are several damaged bricks with voids that exceed 25mm.

I'm concerned about using lime mortar at depth in case it doesn't harden.

Can I make a concrete with larger aggregates to fill the larger gaps or best to shave down bricks and use these to fill instead?

Many thanks

 

[Cubist]

Theres nothing to worry about. Lime mortar will happily cure at depth and provided it can secure the needed bonds to the surrounding materials it will easily do what you need of it.

 

[Flyfisher]

Or use a weak NHL2 mortar perhaps?

 

[Lacan07]

Hi all,

About to embark on lime plastering the back of an inglenook fireplace. The plan was to point up using lime mortar prior to plastering.

Old soft brick and after stripping off some cement render there are several damaged bricks with voids that exceed 25mm.

I'm concerned about using lime mortar at depth in case it doesn't harden.

Can I make a concrete with larger aggregates to fill the larger gaps or best to shave down bricks and use these to fill instead?

Many thanks

View attachment 16241

Yes, if you have some of the original bricks spare just smash one up to create some stones to push into the lime mortar beds. This will help the lime mortar to avoid cracking which is main risk when filling larger voids. Very briefly dip the brick stones in a bucket of water before adding to the mortar.

 

[Kearn]

A hairy mix, hemp putty or traditional daub will happily go to that depth…just. Or as said, add in broken bits of stone/brick/tile to pack the void out and enable less thick lime to need time to go off. Thicker lime = slower and more prone to cracks.

 

[Stevers]

That looks to be an interesting mix of stone and brick, fireplace openings are one place where exposed masonry and stone looks entirely at home.

 

[aockenden]

Another decent option is NHL2 + rough hemp shiv. SHould definitely harden up properly but also remains lightweight and easy to bulk fill big voids in a single go.