1790s stone cottage moisture and salts. PIV?

[damp+dusty]

We are starting to look after a 1790s stone cottage that we have very gratefully inherited. We have been reading previous posts with great interest and would value the forum's experience with our building please.

The inside of the cottage feels damp. If we are on holiday for a couple of weeks we return to a really damp feeling and smelling building. There is condensation streaming from the glass in the mornings and there are a couple of salt patches on the walls at ground floor.

We think we need to reduce the moisture inside in the building. It currently has a log burner and some electric infrared heaters downstairs. Upstairs there are radiators that run off the log burner ie only work if the log burner is lit.

We have discovered that in the late 1970s the property was given a silicon injection DPC and then the ground floor walls were rendered internally with a finish that included a Peter Cox salt retardant additive.

The first floor walls are plastered in a more standard way although we do not know if it is lime. We have only ever painted with breathable paint since it was re-plastered, also in the late 1970's.

We are wondering whether the internal rendering might be preventing moisture from escaping the cottage as easily as it otherwise could. We would value thoughts on this, especially as the work was done in 1979 - will it still be working / preventing moisture getting out or does it eventually stop becoming a barrier?

The internal render is not particularly attractive so we were thinking of plastering over with lime plaster but now we are thinking that lime plaster over render is wrong because the render is less breathable. Is that correct?

The ground floor is a concrete slab. Do we need to replace that with limecrete to make it more breathable?

We are considering fitting a positive input ventilator in the roof, perhaps with heating option to try and increase the overall temperature within the property which faces north onto a road with another house only 6m away so limited sunshine/solar gain. We are not sure whether this will be successful though because of the internal render potentially preventing the moisture escaping?

We are also considering fitting additional fans to the bathroom and kitchen with moisture sensors so they come on automatically (hopefully to help with human/teenage error).

We are going to replace the 50 year old log burner with a new more efficient one and also fit electric rads upstairs (to hopefully run off PVs). BTW there is no gas in the village and we do not want to install oil at this point.

We'd be really grateful for any thoughts regarding the above. Keen to make the right decisions for this old cottage! Thank you

 

[fernicarry]

electric rads upstairs (to hopefully run off PVs).

PV production will be very low (negligible really) in mid-winter just when you need the radiators so don't expect it to do much to offset the running cost. If you have a big hot water cylinder (which you'll need anyway if you fit a HP), divert the solar production in summer into immersion heaters and you'll get free showers.

additional fans to the bathroom and kitchen with moisture sensors so they come on automatically

Definitely have extraction in the bathroom and kitchen. I've found the moisture sensor (hydrostat) on my central extractor to be pretty useless. Its adjustment is on a knife edge. Slightly too high and it runs for ever, slightly too low and it rarely comes on, I gave up fiddling with it. For the bathrooms I have flow switches on the shower and bath pipework along with delay start and overrun timers that connect to the boost terminal on the extractor. The same flow switches also bring on the mirror demister and towel rail so the showering experience is fairly idiot proof.

The central extractor is always running in trickle mode so its effect is like PIR except in reverse drawing air out of the building which is replaced by new air finding its way in through gaps in the fabric like around windows and doors, between floorboards etc.. Generally I find this greatly reduces condensation on the windows except this winter it hasn't, probably because outdoor temperatures have been bouncing up and down so much.

 

[alexander]

the cement render will be holding in water that needs to be removed, it really depends on what is happening outside if its been repointed, painted, rendered in modern paints or cement then what you do inside is not going to make a great deal of difference, piv unit will only take moisture out the air it will not dry out the structure of the building regardless what people claim

 

[aockenden]

I think you need to focus your lexicon when describing your situation. “Render” is not specific enough for us to understand the issue. The word render usually just means sone kind of thick layer of some kind of mortar applied onto a masonry wall (some people would say the term only applies to external coatings). So you could have a clay render or a cement render or a lime render, etc.

The first couple steps I would take in your shoes are

1: Confirm the actual materials used for the internal plastering / rendering down through all the existing layers of coatings until you hit raw original masonry. So for example, layers 1-3 might be modern paints, layers 4-5 might be gypsum plaster, layer 6 might be cement render, layer 7 might be lime plaster and then layer depth 8 might finally be your original wall’s masonry (stone, brick, etc). Do that both upstairs and downstairs on any wall you don’t have 100% understanding of. It’s impossible to craft a remedy without a deep knowledge of the existing building fabric.

2: Repeat step 1 for the outside of the building.

3: Verify the height of your external ground levels relative to your internal finished floor levels. You will want a decent laser-level to do this properly. No guessing. Do this around the entire perimeter of your ground floor.

 

[mardinor]

It sounds like much of the 'damage' was done in the 70's, yet it is unlikely the house has been as damp and smelly as you describe for 50 years. I would be looking first at what has changed recently, before tackling the earlier issues.

 

[Stevers]

My experience is that stone houses that aren't lived in even with no cement or gypsum plaster in the mix become damp in the winter. Our unmolested 1879 town house, built with good quality Mendip limestones and complete with a full set of sash windows - hadn't been lived in for 18 months, and even the internal shutters on the windows were damp when we had it surveyed. Before we converted our heating to have smart radiator valves (i.e. now always 'on'), the point at which the heating was turned on was when the house became cold and clammy, this happened in late October early November each year - it is a man made cave after all!

Traditional houses that aren't lived in are musty houses unless sufficient heat and ventilation is provided - that's just the way things are.

 

[ThornhillMike]

I'd echo Steve's comments. Our renovation project subject had been empty for three long, cold, wet Manx winters closed up and unheated. With the roof replaced, vile carpets all gone, intermittent heating on, after eight months the place has stopped smelling like the bottom of a rugby kit bag (I know that smell...). I'm with the others, before hacking the place to pieces try and establish what recent conditions have given rise to your predicament.