Old Soot Coming Through Wall From Unused Chimney

HowAreYeGettinO

Hi all - hope I'm posting this on the right forum.

The oul' fella has an old house that he would like to rent. As it was built in the '50s it has chimneys everywhere. He didn't want potential future tenants to have a fireplace in their bedrooms, so he got the fireplaces blocked up with plasterboard.

Problem now is that brown streaks are appearing on the walls above the fireplaces. It looks like this is old soot that is coming through the wall from the chimney flue.

Would anyone have an idea what might be causing this and possible solutions? All help greatly appreciated...

Mellor

How do you know its soot and not damp?

Poor Uncle Tom

Plasterboard cannot block up a chimney. The fire front room opes were blocked up with plasterboard. The chimney's are probably still open to the outside elements. If the fires are not lit on a regular basis the chimneys act a concrete sponges soaking all the rain and dampness into the house and never being dried out. The chimenys need to be sealed off at the top.

If it is wet soot that is soaking through then it means there was never linings put in the flues.

HowAreYeGettinO

Thanks for the replies folks.

The chimneys are still open to the elements alright, there are just crowguards in the chimney pots.

Poor Uncle Tom - you say the chimneys need to be sealed off at the top - is there a particular type of 'cap' that suits this scenario? I assume you couldn't just block it off, that you'd have to put something there that still allows air to circulate so that the flue could begin to dry itself out?

Poor Uncle Tom

Traditionally a lead sheet would be shaped over the top of the pot to stop direct rainfall entering the core. This is the easiest most effective way of stopping the bulk of the moisture entering the chimney block, simple but it works.

Go into the attic and check the chimney bulk itself, check if it is damp/wet to the touch, I bet you can also smell soot in the attic, and you may even be able to see leeching through the chimney block. If it is this bad I would advise opening up the friefronts again and light fires for a week to dry out the chimney block, then get the chimneys cleaned, closed at the top and covered/closed at the fire front area.

Please note that if there is a fireplace you will never use again, then the chimney should be taken below roof level and the roof slated/tiled over, imo.

PureBred

I had the same problem in the house i'm doing up at them moment. If the house was built in the 50's then i doubt there was evere linings put in the flues.

The chimney bulk itself is prob damp/wet to the touch as a previous poster said.

I completly took out the chimney so i didnt have to worry about it.

I agree with poor Uncle Tom that you should take the chimney below roof level and finish the roof accordingly. It should dry itself out after this.

You'l prob have to remove the plaster board though as that stuff really likes to saok up the black soot. You mite get away with painting over though if it dries out enough.

Fries-With-That

HowAreYeGettinO wrote: »

Hi all - hope I'm posting this on the right forum.

The oul' fella has an old house that he would like to rent. As it was built in the '50s it has chimneys everywhere. He didn't want potential future tenants to have a fireplace in their bedrooms, so he got the fireplaces blocked up with plasterboard.

Problem now is that brown streaks are appearing on the walls above the fireplaces. It looks like this is old soot that is coming through the wall from the chimney flue.

Would anyone have an idea what might be causing this and possible solutions? All help greatly appreciated...

The reason you have brown streaks appearing on the walls is because whomever blocked up the chimney didn't leave a vent in the fireplace.


You don't need to cap the chimney the wire cowl yo have in place is all thats required to stop birds nesting.

What you need to do is cut a vent into the plasterboard and cover the hole with one of the many vents available from diy outlets.

Its best to buy the vent first and mark its size on the plasterboard before cutting.
Don't get one that gives prospective tenants the option of closing it, to prevent condensation and leaching of the soot through the walls it must remain open.

What this does is it allows the chimney to vent naturally and maintains the chimney in a dry condition.

If its an old house it won't do any harm to have this ventilation in the room as it will also prevent condensation in general(especially if the room has been fitted with pvc windows).


The other problem you'll have is covering the brown streaks, buy one of the many stain block coatings on the market, in my experience polycell stain block in an aerosol can is excellent.

Spray on the stains leave to dry, apply a second coat after first has dried, leave 48 hours befor applying whatever paint you want as a finish colour.

Note of caution....always wear a dust mask when using aerosol paint products.


More info on chimney damp here.
http://www.buildingconservation.com/articles/services/chimney.htm



Regards

Fries.

HowAreYeGettinO

Thanks for the help everyone. Much appreciated.

Fries-With-That, for the chimneys that are not being used, wouldn't it be a good idea to get them capped anyway to stop rainwater coming in?

Fries-With-That

HowAreYeGettinO wrote: »

Thanks for the help everyone. Much appreciated.

Fries-With-That, for the chimneys that are not being used, wouldn't it be a good idea to get them capped anyway to stop rainwater coming in?

In my opinion if you are intent on getting these chimneys capped you'd be well advised to use one of the open caps that will still allow the chimney to breathe. one like this would be ideal.

http://www.eurocowls.com/i/abr1.jpg


Regards,

Fries.

Poor Uncle Tom

Personally I would cap off any chimney I was not going to use because the average rainfall in the eastern side of the country is 880mm per year and 1125mm average in the western side.
http://www.met.ie/climate/rainfall.asp

For an average 220mm bore chimney pot that comes to 33.5 litres of water in the east of the country for each exposed chimney pot and 42.7 litres of water in the west of the country.

Imagine that 7.3 gallons per year for each chimney pot in the east, and 9.4 UK gallons per year for each chimney pot in the west.

Natural ventilation will not dry that out, imo.

HowAreYeGettinO

OK - sounds like a vent in the plasterboard, combined with an open cowl on the chimney pot is the best course of action for now - I doubt the old man will undertake the expense of taking the chimney below roof level etc.

Really appreciate the help given here folks. Thanks again.