Chimney - re-rendering, relining and cleaning

psicic

Hi,

I'm looking for a bit of info about fixing the rendering on a chimney, installing new chimney pots etc. I have an old cottage(one storey) with one chimney that has moderate damp in it. It's a stone chimney (other chimneys on house are much later, are concrete brick and don't leak).

Rendering

Problem is render is cracked and a large part of the render came off chimney last year during extremely cold weather. (This is likely due to someone back decades ago using newspaper, sand and straw beneath the render as some sort of filler for some inexplicable reason. I wouldn't rule out the possiblity that there may haven been a snall chimney fire a decade or so ago in the chimney that started this 'cracking' of the render.)

First question is, has anyone here rendered their own chimney? (In case I'm using the wrong phrase, by 'render' I mean plastering the outside of their chimney with concrete or whatever).

What mix of materials did you use, and is there need to add a waterproofer to the concrete mix?

If it was a stone chimney you did, did you use a different mix/substance to 'fill in' the uneven surface underneath the render first?

I just plan to use a roof ladder to do this job. If anyone has done the job themselves here, did you find that was enough, or should I seriously be considering chimney scaffolding?

[surprisingly the flashing is fine and can be reused/left in situ]

Chimney Pots

When I got up on the roof to have a look, I noticed that the chimney pots are actually some very, very old, very large gauge Wavin piping that is weathered like an onion. The pots are so wide (up on 15-20 inches) that they'd let in a lot of damp even if the rest of the chimney was perfect. I'm planning on replacing these chimney pots with more normal sized modern pots - I assume I'm also going to have to replace the chimney cap/chimney coping (i.e. the rectangular bit of concrete that the two chimney pots sit into - not sure what the correct name for this is). Can anyone give me an idea where I could get this? (House is in Roscommon near Ballaghaderreen, but I live in Dublin). Anyone have an idea of the rough cost?

Flue Liners / cleaning

I plan to, ultimately, put in two flexible flue liners in the chimney. However, the chimney needs a very, very good clean first. It's an unlined, stone chimney that was badly treated for decades and is just riddled with damp at the moment. Once I have it rendered and now that we're heading into good weather, it should dry out. Other than a good brushing, anyone have any good ideas that will help get minimise/reduce either the staining or that heavy smell of ancient turf fires from the chimney.

The Chimney pots/ rendering tasks are not tasks that I'm particularly gung-ho to undertake as DIY projects - lots more to do on the house - but if the weather happens to be good this weekend (and I haven't found a trades person able to do the job for the right price) I might get a push on and at least get the rendering done.


Any advice/comments appreciated.

AckwelFoley

Im a bit stuck for time so i'll be brief, il try give more info later..

The lining is the first job, render is the last.

There are a numner of methods, one is to line it with chimney flues like a more modern chimney, its a day job or so, it does include however cutting access into the chimney stack

The capping can be bought precast, however i prefer to cast it in situ, particularly if it is a double flue, but done right its a much better job in my opinion

The render is mixed at 6 sand 2 cement 1 lime, the coats need to be the same, but make sure the scratch is not stronger than the finish ie the napp finish coat or else there is risk of cracking

I would recommend you re flash the chimney, if you are getting the job done right, although having said that, it mightnt need to, id nearly want to see it.

Use angle beads on th chimney once you have the scratch coat done, get the single coat pvc bead, the double wont work too well with an old brick chimney, so get a goo stright scratch on and then the bead

psicic

Thanks snyper, especially for pointing out there's not much point focusing on doing the rendering without doing the flues at the same time.

All in (and especially since it's a one storey building) it seems quite doable. Probably more of a three-day-to-a-week job for me, but sure isn't that what annual leave is for!!!!

Not sure about casting in situ - mostly because I'd never considered this until your post - but I'll look more into this.

You're probably right about the flashing - silly of me to be trying to scrimp there of all places.

Another really basic question, when I'm cleaning out the inside of the old chimney, before putting in my flue liners and insulation, is chimney brush enough, or would you use any type of additional cleaner (e.g. to reduce old smells or anything)?