what is the stone used in the walls ?

gg

Traditionally in exposed areas stone work was never left unprotected,
It is unfortunately a legacy of a Victorian myth that rubble stone should be exposed.
Around here, "Heads of Valleys" South Wales the exposed elevation was always slate hung or in later times clad in corrugated iron known locally as wriggly tin.

Yanntoe - If you are going down the render route to prevent water penetration I would suggest putting on EWI using EPS as the industry standard system with thin film acrylic or silicon render. This will give good (water proof) weather protection, allow a level of breathability to the wall and of course will give some thermal advantage depending upon the thickness chosen.

Oh, and here are a couple of links with a lot more explanation:

https://www.buildingscience.com/documents/digests/bsd-105-understanding-drainage-planes

https://www.mtidry.com/blog/wp-content/uploads/2018/03/Drainable-is-Sustainable.pdf

Posted By: YanntoeThanks Peter,
Sadly, the detailing on the relevant walls (Victorian barge boards, fascia boards with cast Iron rainwater gear, conservatory etc.
) mean that anything thicker than around 2.5 centimeters depth won't work without major work so not really an option.

assuming your walls are 500mm thick with 20mm internal plaster, a quick calculation gives U of 1.65
Put 20mm of EPS EWI on gives a U of 0.87 a useful reduction in heat loss. If you put up 50mm EWI then the U is 0.51 With insulation it is the first bit that makes the greatest difference after which it is diminishing returns.

Architectural goods (fascia boards with cast Iron rainwater gear etc.) can be removed and replaced on top of the EWI. Detailing around windows can be made up with an additional layer of EPS. Conservatorys are more of a problem but I have seen a step in (reduced thickness) of EWI starting about 200mm from the conservatory. It actually looked OK.

I have used them on a Derbyshire (?Gritstone, maybe limestone?) house. The product I used is not the well-known one. I'd still get one that claims breathability since we probably all have our stories of 1980s/1990s silicone-based 'sealers' sealing moisture *in*. The house in question receives most of its rain horizontally and, while it obviously did not stop all ingress, it improved matters significantly. That was about 10 years ago, but I only got feedback for the first year or so.

Many thanks Nick, Owlman, I have my eye on a "breathable" product which if the price reflects it's "efficacy" might be OK. I'm only going to do the exposed walls at the West and the North of the property and clearly I have a small concern that if water gets in it will find it difficult to get out, but the current solution of re-pointing it with some "better" magic lime ... again, isn't an attractive proposition.

Don't get me wrong, I like the look of lime so much better than cement and as long as the area it's going to be used in is somewhat sheltered, then great.

However, I've given it a really good go, with lots of negative comments from the locals and I have to admit that for chimneys, and chimney tops, together with exposed or North Facing walls I'd say use white sand and cement for a lime look or point it all up with SBR/mortar, leaving about 12 mm or so for "decorative" lime pointing to match the rest of the house.

I guess if there are no "reveals" round the windows it might be OK but if the wall is wet in July, its wet all year which means, even if the water doesn't make it through the structure it's going to make the whole thing very cold.

Who knows - If the walls can be made dry, then perhaps the need for additional EWI is obviated!

Hi Yanntoe, have you looked to see whether any of the manufacturers of silicate paints offer a clear exterior product? Silicate masonry paints often being claimed as a highly breathable option... Also, have you spoken to any of the conservation material suppliers/experts, our local one is Womersleys, there's Mike Wye and others no doubt.
..

We found that solving an issue in one location just moved it to another, any water getting in the wall just moves somewhere else to get out if its original exit is blocked, so end up chasing your tail. Silly things like poorly executed phone and tv aerial entries caused problems. ( just needed a decent drip loop) , make sure any drains in windows and drips are present and clean, over windows a lead flashing dressed into the mortar can help encourage water to drip away from the wall and doesn’t look unsightly. We’ve accepted that after prolonged bad weather there will be some penetrating damp, its now more a case of dealing with it, must be said that having dried the walls out over the years it does seem that their ability to “buffer” a degree of damp has much improved. like yourself its just one exposed corner that really suffers.
On another building i did i was advised to add double boiled linseed oil to the mortar mix ( in that instance nhl 5 like yourself) to improve the water shedding ability of the mix.I’m sure you must have done so but standing outside watching how the water acts on the building in terrible weather really helped understand how much was hitting the wall and how it acted.

Hello Yanntoe, I've experienced all the problems you've mentioned, and sympathise with the frustrations of trying to reconcile the apparent inconsistencies between the pro-lime anti-waterproof enthusiasts on one side and the enthusiasm for wanting to enjoy original features and elegance on the other.
Our house is of a similar age to yours, and we went down exactly the same process of enthusiastically hacking off sheets of decaying external cement render that was clearly responsible for the damp problems.

Like you we followed the standard pro-lime advice here, and used a local firm experienced in repairing period properties to clean off all remaining cement, sand-blast the stone and brickwork, and repoint with lime mortar.
The result was beautiful. The lovely colour of the revealed stonework and lime mortaring was a revelation compared with the previous dozens of coats of white sandtex, nicely set off by the sandy red brickwork framing all the windows and doors and with low brick arches.
Then came autumn, horizontal rain for days on end, and water seeping through the walls visible on the inside. The "breathable" limework appeared to be porous, and clearly revealed the wet outlines of stones on the inside, spoiling old wallpaper that had been there for years. It was much worse than even the decayed cement render had been.

Like you, I'm appalled at the prospect of wasting a lot of money having the walls done "properly", only to be told that really all the elegance needs covering up again with ghastly cladding or the house turned into a corrugated iron shack.

So my solution was to wait until the next summer and the walls were dry again, and spray Screwfix "No fuss" damp proofer over the weather-facing walls. I generously sprayed the spirit-based stuff until it the wall seemed saturated. It's an eye-opener to watch the way lime mortar just eats it up - it's no wonder the walls are damp inside when they are deliberately made so porous.
I have to report that this treatment has entirely cured the problem. Four years on, the walls are dry inside even in the wetest winter. The only problems are very localised, the result of salt encrustation and eruption attracting moisture, cooling, and inducing further condensation at those points.
I don't know how long it will last, but it's cheap and easy to apply, and once every 10 years would not matter, and a lot easier than regular repainting.

I've heard other similar stories from people who have been persuaded of the merits of lime - I do thinks it's a pity these are not more honestly set against the pitfalls that can arise.

We have Beeck paint on our lime render - they also produce a transparent preservative for stone.

They don't carry statements like this for the Screwfix product: "H226 - Flammable liquid and vapourH304 May be fatal if swallowed and enters airways.H336 May cause drowsiness or dizziness.H319 Causes serious eye irritation.H340 May cause genetic defects.H350 May cause cancer.H411 Toxic to aquatic life with long lasting effects." though you do need to take care with the acidic conditioners.

We also have some Stormdry inside our showers to protect nearby lime plaster. It seems to work.

Thanks all,
Looks Like Stormdry might fit the bill so we'll give it a go - not cheap though! Just need it to stop raining for a few days - which here in West Cumbria might be next May!!

Posted By: YanntoeConcerning breathabiliy, my contention is that the house is built of stone which is not breathable, held apart by lime pointing which allows air and water into a cavity which is filled with rubble (no Lime) and there is air travelling around this internal "space".

Posted By: YanntoeThe issue with the reveals is that the stonework beneath the upstairs windows is a single stone thick and this extends down to an internal lintel which carries the floor joists etc, these are Victorian and sit behind the slate lintel which is in turn above the downstairs window.

I'm not sure form the above whether you have a rubble filled wall, solid dressed stone, or both. However there are known problems in the situation when you have an exposed wall + lime mortar + impermeable stone, particularly when voids in the rubble filling facilitate the passage of water. The best source of information on the subject that I know of is English Heritage's 'Damp Towers' project, particularly this transcript: https://historicengland.org.uk/content/docs/research/damp-towers-conf2013-programme-transcriptspdf/

If you want to preserve the stone external face then a surface coating may be the only solution, if you can't find and plug a specific ingress route. If you were at an earlier stage when you could tolerate more disruption, then grouting the voids in the wall (if it is a rubble-filled wall) may have been worth considering, though it would probably have been expensive. An external lime render would have been an easier and cheaper alternative.

My stone walls (and others in this area) are of basalt rock because that is the local stone. The stones were used undressed, as found, and at best selected for shape (it is just too hard to dress). The construction is an inner and outer leaf of undressed stone with earth/rubble infill between the leafs. This construction was (is) always rendered both sides. When I have removed the rendering for repair I have always been surprised at the howling gale blowing through the wall. The original render is sand/lime mix, replacement render is a sand/lime/cement mix.

Given the above construction I can imagine that wind blown rain would penetrate the walls easily (as does the wind) and without rendering or other protection (e.g. EWI) problems would arise.

Some 30 miles away another area used red sandstone as the building material. The sand stone was dressed and fitted using a thin layer of lime mortar. Usually such walls were built as solid walls i.e. without rubble infill. often such building were not rendered outside, just internally.

Areas without or with little stone used adobe type sun dried mud (clay) bricks rendered both in and out.

The construction methods had little to do with what made a good building and everything to do with how far you wanted to transport materials by ox cart.

My point is that over here the stone rubble walls were always rendered both sides for weather protection and wind exclusion and the rendering was an integral part of the structure which also added to the stability of the wall.

A failure in the roof of the stone /rubble walls meant that the inner filling was quickly washed out followed by the collapse of the wall. A roof failure of the adobe type building resulted in the structure 'melting' The sand stone structures can withstand a roof failure for some time without damage to the walls.

Posted By: Yanntoea modern, watertight structure which is inherently warm and dry, and light!!

= CARAVAN


gg