internal brick chimney

[Fordy]

Howdy all,
Yesterday we decided to take the morter\plaster off our existing chimney. What we found was that the bricks are in reasonable condition but the mortar inbetween will need some work. My question is the morter is crumbly so is there anything we can paint over the top? some type of clear varnish to help stop all the little bits of mortar falling out??

Thanks

We are in the process of replastering the room as we had flat iron walls before that had buckled a bit. Luckily for us the pressed tin roof is in good condition so that stays..

[Zed]

you'll need to "re-point" the bricks. get some mortar mix from bunnies, clean outr the crumbly mortar (dont need to get rid of all of it just the loose stuff) ,mix the mortar to a goldilocks consistancy/runny-ness and then jam it in between the bricks so that they are covered nicely, smooth it out so that the texture is ok then you can paint over it or render or whatever....

the thing is that mortar is meant to be "sacrificial" this means that over time instead of eating the bricks, any moisture etc decays the mortar instead - thus the need to re-point!

[ozwinner]

the thing is that mortar is meant to be "sacrificial" this means that over time instead of eating the bricks, any moisture etc decays the mortar instead - thus the need to re-point!

That may be true in monkey land, but not where us humans live.

The only reason that the mortar is crumbly is because it is old lime mortar.
The cement mortar us humans use will stay hard for 100's of years.
So will never need replacing, if it does it wasnt made right in the first place.

Oook, oook......

Al

[Zed]

That may be true in monkey land, but not where us humans live.

The only reason that the mortar is crumbly is because it is old lime mortar.
The cement mortar us humans use will stay hard for 100's of years.
So will never need replacing, if it does it wasnt made right in the first place.

Oook, oook......

Al

I sit in me tree - corrected. I humbly bow to harold steptoe.

[journeyman Mick]

I sit in me tree - corrected. I humbly bow to harold steptoe.

Zed,
careful there, I don't think it's possible to sit in a tree and humbly bow at the same time - even for a simian. We definitely don't want you out of your tree .

Mick

[ozwinner]

Too late Mick Im afraid....


Al

[Fordy]

Thanks guys,
Sounds like a job for this weekend...

[wombat47]

Be very wary of using cement mortar to repoint the brickwork -

>The cement will eat into the old mortar
>The colour won't match and patching will stand out like the proverbial
>Old bricks will be softer than the new cement mortar and movement will cause the bricks to crack.

Use can either use lime putty neat or use a lime putty/sand mortar mix (1:3) to remortar joints.

You can make lime putty by soaking hydrated lime in water for at least a fortnight (it will keep for at least a couple of years if not allowed to dry out). I'm not sure if you can buy it ready prepared in handyman size packs - it's not available where I live, but then, not much is.

Don't be put off by the softness of your existing mortar - it is supposed to be soft anyway. Just brush off any loose material. If you aren't too experienced with a pointing trowel, you can apply the putty using an icing bag and nozzle (don't use the one you conveniently found in the kitchen!!) and spread over the joins with your finger. The lime putty is smooth, buttery and easy to use but wear a disposable "surgeon" type rubber glove. The mortar will harden as it slowly dries.

Don't coat the chimney with any sort of sealer - that will lock any moisture into the bricks and mortar.