and the damp came back, they thought it was a gonna, but...

[Bitstreams]

yes, the walls of the dining room are starting to fall to pieces again.

The plaster underneath this section is the wrong stuff - it's a white cement based abomination and I know what I have to do (remove it, let it dry out, lime plaster etc etc) as I have done in other parts of the house.

however, that's not the question..

These patches on this particular part of this particular wall are where the chimney is. Most of the walls are stone and this used to be an external wall. The stone sections seem to be holding up well but the brick chimney is cut in to the stone (or the stone is built around it). In the lounge (where the fireplace is) there are salt deposits on the exposed brick at the back of the fireplace (we have a woodburner).
What's likely to be making the chimney wet - it's capped at the top - would rain coming down the chimney do this? and would that be normal? or is it more likely that the bricks are soaking up moisture at ground level? There's no damp around the chimney breast upstairs.

So many questions I know.. sorry.. here are some pictures because everyone likes pictures..





regards
Simon

 

[worms]

Perhaps I am not understanding the description, but is the damp through the wall from the salt deposits? If so, is it not likely that it is simply the salts in the wall absorbing moisture from the atmosphere?

 

[MdB]

I'm not quite following this either. I take it this is an internal wall with a fireplace on the other side? If so, the damp is likely to be coming from above or below and us unlikely to be condensation. Salting also suggests that the moisture is coming from the middle of the wall outwards.

Moisture down the chimney is an option but I thought it would be unlikely to come down the entire distance and only show its self at the bottom. This leaves rising damp. What are your ground levels like compared to floor level? Do you know what your ground water level is like? Are there any pipes running under your floor?

 

[middi]

Obviously difficult over the forum to see what the problem is-- BUT :-

1) The " salty" deposits do not last very long and never reappear if the salt/minerals provenance is from within the bricks as these deposits will eventually be leached out of the brickwork by natural evaporation processes regardless if they are covered in cement or not.

2) the " salty" deposits will never be eradicated if the moisture is drawn ( or sucked) from ground level as there is an endless supply down there. The moisture laden with salt/minerals will be drawn into the bricks in the wet cycles and as the air partly dries the wall surfaces water evaporates and the salt line appears.

You will have to draw your own conclusion as to whether you should get an expert to have a proper look at it, or to believe my non scientific understanding of the problem as you describe it.

Middi

 

[Lime]

What's likely to be making the chimney wet

Condensation in the chimney from the woodburner perhaps?
Burning wood can produce prodigious quantities of water and unless the woodburner has a complete intact liner, is designed to allow condensation run-back to the fire (or to the outside) and is sealed from the chimney void it may be the source of your damp.

 

[MdB]

What's likely to be making the chimney wet

Condensation in the chimney from the woodburner perhaps?
Burning wood can produce prodigious quantities of water and unless the woodburner has a complete intact liner, is designed to allow condensation run-back to the fire (or to the outside) and is sealed from the chimney void it may be the source of your damp.

That's a good point.

 

[Bitstreams]

Can anybody expand on this..? this is what the woodburner looks like from the fireplace side.



I can take the plate, that the pipe from the burner goes through, down and have a look (but not until after my mum has come to lunch tomorrow :roll:

I suppose you are talking about putting one of those concertina-type expanding flue's inside all the way to the top of the chimney. The chimney isn't straight so could this still be done?

Simon

 

[MdB]

What sort of fuel are you burning? is it wood? if so, how wet is it?

I'm thinking that the damp patch is really too low down to be caused by moisture condensing in the chimney but I guess it could be a contributing cause.

 

[Bitstreams]

Yes we are burning wood - all sorts really but the logs are stacked (under cover) outside and then dried a bit more in the fireplace, though we also burn pretty much any scrap wood that isn't nailed down.
I wouldn't have said any of it was really wet. You're right that the damp patch is only 3-4 brick courses high at most, well below the level of the cover at the base of the chimney.

 

[vicky whitworth]

I don't understand how the chimney can be capped but have an active flue inside it. Where does the flue vent to if not up the chimney?
Would the damp be at about the height where warm air rising from the room and the woodburner meets the cold air dropping down the chimney? We have a bit of this problem and we get rust on our pipework as a result.

 

[Bitstreams]

Sorry, when I said capped I meant that there is a flat cover to the top of the chimney, raised on brick pillars, rather than chimney pots.

 

[vicky whitworth]

Ah. When we had a similar problem and then rust appearing at the top of the wood burner flue where it went into the chimney our chimney sweep said that the cowl arrangement wouldn't actually keep out that much driving rain - it's often horizontal rain down here in Devon. So the rain was running down in the gap between the liner and the brick chimney and accumulating when it couldn't go down any further because of the register plate, and then the damp spread out. Perhaps you could look at changing the cowl arrangement?

 

[Lime]

the rain was running down in the gap between the liner and the brick chimney and accumulating when it couldn't go down any further because of the register plate, and then the damp spread out. Perhaps you could look at changing the cowl arrangement?

That suggests that the cowl wasn't fitted/sealed properly at the top of the stack.
When driving rain enters the cowl it should all trickle down the inside of the liner to the fire.
If the rain is getting into the chimney void there must be an opening somewhere that should be stopped up.
Of course liners age or get damaged with too much heat and disintegrate in the chimney too.
The low temperature single skinned liners do not last long with a hot wood fire.

I wouldn't have said any of it was really wet.

Wood nearly always contains a large amount of moisture held within it although it may appear quite dry on the outside.
Even dried wood still contains a considerable amount of water.
The hot water vapour is released into the flue and will condense out on any cold surface. (along with the tar)

 

[Matt Green]

That doesn't look like condensation damage.

What is the construction of that tiled floor? Does it have a DPM?


M.

 

[Bitstreams]

The tiled floor is on to new-ish concrete, below the concrete (about 2" thick) is some brick pammets and some old concrete. I'm guessing that there's no DPM under the pammets as they looked pretty old and the same for the old concrete.

 

[Matt Green]

The tiled floor is on to new-ish concrete, below the concrete (about 2" thick) is some brick pammets and some old concrete. I'm guessing that there's no DPM under the pammets as they looked pretty old and the same for the old concrete.

You have plastered the walls all the way to the floor. Any water trapped beneath that floor is going to move into the plaster at the wall/floor junction and evaporate through the base of the wall. Hack out a channel of about 50mm height from the base of the plastered wall, then remove the affected sections of damaged plaster, allow to dry, then repair. Affix a (pre-treated) skirting board over the channel to hide the gap and your problem should disappear as any water will now evaporate behind the skirting.

M.

 

[MdB]

Ah, that rings bells. When the new concrete was laid, was the plaster removed from the base of the wall or does it go down below current floor level? Plaster is very good at sucking moisture up from below and hence a damp wall with salts as the moisture evaporates. We had this issue all around the base of our walls so should have thought of it earlier. Our solution was to replace the floor and the walls ( :shock: ) and redo properly. I can understand that this won't be what you want to do so something along Matt's lines sounds good. I would argue that little moisture will evaporate through the skirting and that the wood will rot eventually but this will be an easier job to replace.

 

[LadyArowana]

I would argue that little moisture will evaporate through the skirting and that the wood will rot eventually but this will be an easier job to replace.

Or you could ventilate the skirting so the moisture escapes.

 

[MdB]

Neat carpenters your mice. Our rat made far more of a mess:

(There were attempts at digging all the way around our old walls. Fortunately, this particular rat is having a rest from digging a couple of foot down in our garden at the moment.)

 

[LadyArowana]

Neat carpenters your mice. Our rat made far more of a mess:

(There were attempts at digging all the way around our old walls. Fortunately, this particular rat is having a rest from digging a couple of foot down in our garden at the moment.)

Very important to get good quality rodents!