Chimney damp?

[baldbrewer]

hi,
we have recently bought a cottage that comprises of 3 parts, the stone built part from 1750's, the middle rendered brick part from early 1900's and the last rendered brick extension was completed in the early 1980's.

Whilst installing a light fitting on the wall of the 1750's cottage and between the 1900's bit I started to peel the thick embossed wallpaper off to gain some more slack on the cables and being previously concerned at what the plaster would be below I kept pulling.

On the positive side it came away very easily but there was some lining paper below which also came away easily to reveal the damp in the attached photo.

in the dining room in the 1900's bit there used to be a fireplace installed which is now hidden behind fibreboard panelling installed by the previous owner.

we knew that there would be some damp issues when we bought the property so I'm not put off by this just want advice on how best to proceed.

I went in the loft this morning and found the chimney as the attached photos.

As you can see the original roof and the new roof was installed above it.

the chimney is open to the cold air loft but there is no vent installed in the dining room.
this is why I think we have the damp in the living room?

How should I address this issue?

install a vent in the dining room above skirting board level?

should I remove the gypsum plaster in the living room?

we do have an exterior wall where the curtain be seen in the dining room photo, the dining room is "currently" about 4" below ground level to a concrete path and wall rendering down to floor level on that side which I plan to tackle after sorting this issue out by removing the concrete path and lowering the path level and potentially installing a french drain and gravel pathway .


apologies if I have wittered on too much , it's our first old property and we want to make sure we do things right.
any advice gratefully received.


many thanks and best regards,
Simon.

 

[baldbrewer]

Hi, does anyone have any advise?
cheers,
Simon.

 

[malcolm]

The chimney doesn't look sensible thermally. If it's completely open to the loft space then the inside of the chimney will be a lot colder than the interior of the house. There will be heat loss and also the chimney walls will attract condensation from the house. I would reduce the opening size at the top. Just by putting a sheet of wood on top or similar. A small gap or hole would be useful to help extract any moisture from in there but it shouldn't need to be must more than a square inch or so. Vent at the bottom isn't the answer.

The damp in the photo is coming up from the ground or from any ground on the other side of the wall. I got a bit lost reading your post. I'll be there because there is more water getting in than can get out again. High external ground levels, gutters spilling onto the ground etc. Or just coverings on both side of the wall too waterproof. What's on the other side of the wall? It's more effective to dry the wall from outside.

 

[baldbrewer]

The chimney doesn't look sensible thermally. If it's completely open to the loft space then the inside of the chimney will be a lot colder than the interior of the house. There will be heat loss and also the chimney walls will attract condensation from the house. I would reduce the opening size at the top. Just by putting a sheet of wood on top or similar. A small gap or hole would be useful to help extract any moisture from in there but it shouldn't need to be must more than a square inch or so. Vent at the bottom isn't the answer.

The damp in the photo is coming up from the ground or from any ground on the other side of the wall. I got a bit lost reading your post. I'll be there because there is more water getting in than can get out again. High external ground levels, gutters spilling onto the ground etc. Or just coverings on both side of the wall too waterproof. What's on the other side of the wall? It's more effective to dry the wall from outside.

Hi Malcolm ,
Thank you for the advice re chimney.
Apologies if my message was confusing.
The green dining room floor level is about 100mm below the outside ground level that falls away along side the living room.(rendered outside photo below)

The wall showing the damp is between
The dining room (where the old fire place was) and the living room.
The damp is on where the back of the old fireplace would be.

But I do wonder if it is damp from the wall being below ground level in the dining room and this moisture tracking to the wall shown.

I’ve done some exploratory digs this morning to make a start getting the gypsum plaster off.
Is the blue colour a distemper coating on the lime at all?
The lime render makes a hollow noise when tapping in areas where I assume it has lost its bond?
Am I best to just removed the gypsum layer or remove everything?

Hope attached photos help.
Many thanks for any help,
I’m new to the forum and look forward to working on our house.
Best regards,
Simon.

 

[baldbrewer]

Hi all,
Please see the photo below of the area of old lime render, lime plaster and gypsum removed so far.
what would you do? remove all the old lime plaster, gypsum etc and completely re render the whole wall with an insulating product such as "Lime green ultra" followed by a lime plaster top coat after a years time?

as I guess many of you have experienced there are hollow sounding areas where the old stuff has blown and solid areas where it still bonds well , part of me feels why create work lol and just patch up where required.

many thanks,
Simon.

 

[larry]

Can you remove the gypsum layer and leave the lime underneath? Then patch any completely blown bits with a lime plaster mix. I've had DIY success with 'breathaplasta'.
Also agree with comment above about breathability outside... What's that paint over your render?? If standard masonry paint I'd imagine that's not helping (basically a cling film layer right??)

Even internally be careful with paints etc you use over the top... Can recommend tikkurilla who specify SD values for paints unlike many other manufacturers

 

[baldbrewer]

Hi Larry,
Thank you for your reply, good question re the exterior paint currently unknown but I've asked the vendors estate agent to see if they can ask the vendor what the paint is.
probably blinkin clingfilm paint like you say lol.
out of interest the blue sandy layer is called blue grit and made by Sika , they have assured me it is breathable.
the gypsum is still come off but holidays have got in the way.
We had a builder round last week about some other works and his input was it is probably the redundant fireplace and chimney causing the damp and he suggested a double height airbrick to be installed in the wood panelled dining room in the previous photos.
not convinced myself so will carry on researching and do as Malcolm said.

I'll have a look at breathaplasta and the Tikkruilla stuff thank you .

we are still going to remove the path away from the rendered wall and eventually raise the render level and install a bell mouth.
Unfortunately due to the dismal July weather cast iron guttering replacement and shrinking mortar chimney fillets are priority jobs now.
one day all will be finished lol.

 

[larry]

Chimney is in the middle of the house right? Could you not full fill with EPS beads up to joists in loft? Would keep it at same temp as rest of house. Agree with Malcolm that the large hole at top will create a big temperature differential that will mean the chimney behind the wall is colder and this will attract condensation on the wall.

Alternatively, damp on walls could just be rising from the ground. If you've got a non vapour permeable wall covering on outside and no DPC in the wall then the wall will just suck up moisture from ground and follow path of least resistance. Solution is to make both sides breathable (lime plaster), and would also suggest considering wood fibre insulation internally which is hygroscopic and will buffer the moisture. But to do the lime plaster you really need to remove any layers that are not original. The sika stuff, never heard of it but the datasheet does not provide an SD or mu value so I would suggest unless Sika provide some confirmation this is vapour permeable you are safer to treat it as not vapour permeable. Ideally you want to hack back anything other than the original lime plaster.

Or course, both factors could be contributing to the damp.


Agree avoid a vent in room, would probably help with the condensation problem as it will increase the temperature in the chimney and hence reduce the differential between the wall and chimney but you'll notice the difference when you try to heat the room!

 

[baldbrewer]

Chimney is in the middle of the house right? Could you not full fill with EPS beads up to joists in loft? Would keep it at same temp as rest of house. Agree with Malcolm that the large hole at top will create a big temperature differential that will mean the chimney behind the wall is colder and this will attract condensation on the wall.

Alternatively, damp on walls could just be rising from the ground. If you've got a non vapour permeable wall covering on outside and no DPC in the wall then the wall will just suck up moisture from ground and follow path of least resistance. Solution is to make both sides breathable (lime plaster), and would also suggest considering wood fibre insulation internally which is hygroscopic and will buffer the moisture. But to do the lime plaster you really need to remove any layers that are not original. The sika stuff, never heard of it but the datasheet does not provide an SD or mu value so I would suggest unless Sika provide some confirmation this is vapour permeable you are safer to treat it as not vapour permeable. Ideally you want to hack back anything other than the original lime plaster.

Or course, both factors could be contributing to the damp.


Agree avoid a vent in room, would probably help with the condensation problem as it will increase the temperature in the chimney and hence reduce the differential between the wall and chimney but you'll notice the difference when you try to heat the room!

Hi, yes the chimney is in the middle of the house, in the process of sourcing the eps beads now. Found the fireplace! the vertical bricks on either side have spalled slightly but main bricked up fireplace is bone dry, still more gypsum and loose stuff to come off .thank you for your replies very helpful.