What sort of damp problem do I have

MikeJG_2

I would be grateful for any advice on the following matter: First some history

Our house was built as a 2 up/ 2 down in the 1820s. In the late 1870s a 2 storey extension was built on the detached side. This included 2 rooms with fireplaces, 1 up, 1 down. Later the house was extended again, still with solid walls, such that the fireplaces and chimneys were no longer external to the house. In the 1970s the house was again extended such that a kitchen covered the rear of the house and finally in 2000 a very large conservatory was erected over the rear of the property.

We moved in in 2010, having had the house surveyed with no damp issues reported. However in clearing out the loft there was a ½ inch gap between the 1870s chimney stack and roof. We had all the chimneys lead flashed but gave the issue no more thought (they were mortar flashed before).

The 1870s 2 fireplaces were now downstairs in a Study and upstairs in our 3rd bedroom. My wife decorated i.e. painted the wallpaper (The whole house is wallpapered except the kitchen, bathroom and conservatory). She noticed that a small bit of paper was lifting from the foot of the Study fireplace but said nothing. About a year ago I noticed this and, using a very basic damp mater ascertained that there was no moisture.

3 months ago we thought that we had sold the house and by following a surveyor around I could see that he had detected some damp around the base of the Study fireplace and just below the ceiling where the chimney stack left the 3rd bedroom. My damp meter showed similer results.

Knowing that the Study fireplace was sealed off just inside I proceeded to make a 4 inch diameter hole in the seal. The room filled with soot! I also asked a professional roofer to cap off the chimneys. He did this simply by gluing slates to the chimney tops. I felt sure that matters improved whilst the chimneys were not capped but certainly got worse afterwards.

I called in a local damp company 2 weeks ago who did a very quick analysis; salts upstairs and rising damp downstairs, we will fix the fireplace and walls (up to 1 metre) for £900. I quickly found the next nearest professional looking damp expert who spent 10x the amount of time here and prescribed ‘bridged mortar’ just above the skirting boards and penetrating damp in the fireplace. He does not go upstairs. For £75 he will fix the skirting boards.

Help! I think it is factual to say that a professional damp meter shows red (and a range of numbers between 3 and 10 on my cheap meter) for a small area just below the ceiling in bedroom 3, the same at the both sides of the base of the Study fireplace and only just above the skirting boards either side of the Study fireplace. Tapping the wallpaper covered walls suggests that all the plaster underneath is sound and there are no stains, discolouration or smells.

I have 2 theories not accepted by the experts; The first is that the fireplace is suffering rising damp but not the walls since improved damp proofing was introduced in the late 1870s but not around fireplaces since the were regularly heated. The bedroom 3 problem will be sorted by ventilating the capped chimneys (in hand) and the small amount of damp above the skirting boards can wait.

The second theory is that I have a condensation problem caused because we always leave the conservatory doors and all internal doors open to dissipate the tremendous heat generated in the conservatory. Is this possible? I have a simple humidistat that shows 60% in the house a lot of the time, I presume that hot air from the conservatory could easily circulate through the house and cause the dampness.
Some input please.

Grenage

Any chimneys sealed off will need to be ventilated; condensation in the stack is your most likely problem.

MikeJG_2

Have anticipated that this might be an issue and have booked a roofer to install air bricks on Aug 5. Will report back if this solves problem. However climbed onto flat roof adjacent to 'chimney stack' roof this morning and noted that water could blow under one of the tiles such that it was in line with and slightly down hill to the top front of the chimney stack in the bedroom. Have just asked roofer to come more quickly if he can (to fix and still install airbricks). I have had 7 water ingresses in the house in 7 years due to water blowing in, so I am on my 8th year!

Doozergirl

You shouldn't seal a chimney off literally, you cap but allow it to ventilate at the top and in the house.

Fireplaces in period properties are genuinely better left open. The problems do seem to occur most on sealed ones.

If your problem is condensation on the walls then if you scrape off some plaster and stick your meter into brick, it should be dry. If the brick is wet, that's when it's seeping through. I had similar on a project and it turned out to be leaking back gutters on the chimney. Water was managing to seep down the walls all the way to the ground and effectively pooling, but evaporating on the walls of the heated rooms above. When the heating went off, we could see it all appearing on the chimney breasts from the roof down.

Chimeny breasts are always tricky.

MikeJG_2

Thanks for the input. When I asked a professional roofer to cap of the chimneys I did expect him to leave some ventilation. Since the fireplaces had both been 'blocked' previously I accepted that sealing the top was the same as sealing the bottom but may have been wrong. In any case the chimneys will be vented shortly.
Scraping off plaster is an issue since all the walls are papered. My real concern is that 2 'reputable' damp proofers have visited and come up with different solutions £825 apart!
For the time being I will ensure that I don't have a leaking roof, get the chimneys ventilated (both low cost) and then see what happens. As things stand you cannot see that I have damp until you stick a meter into the wallpaper.
I am also keeping the conservatory doors shut although this gives a hot conservatory and cold house!