farmhouse do up! the damp from cement & gypsum

[WetWales]

Hello everyone,
I’ve loved reading your advice on here over the last few months. We’ve finally purchased our farmhouse in west wales, a rubble stone wall farmhouse early 19th C with 18c layout…

Ive wanted to post for a while now but don’t know where to start

Ill start with the first problems - damp walls. Ive learnt damp walls are cold walls, learnt that both from living in old farmhouses and reading on here!

Ours has been “done up” over the years and all the internal lime walls have been skimmed with layers of gypsum and paint inside - lime wall all blown and mouldy, it’s mostly all now stripped off apart from internal lath and plaster upstairs walls

Outside has been patched with cement render , concrete, and gosh knows what else, I thought I had but can’t find photos of the front external wall that’s worse …
The lime wash layers are peeling off and are “holding” pockets of crumbled lime , that I assume is holding damp, much of it is green…. Very bad!

As you can see this first picture perfectly demonstrates what you all say about the damp getting trapped in the walls when it can’t breathe and escape!

We are going to put the house as back to original as possible.3 coat Lime on all the walls by a local specialist.

I’ve considered IWI but am concerned about condensation and unwilling to add any insulation at all at the risk for condensation , I couldn’t face doing all this work to then find out it’s not helped!

I’ve thought about a thin coating of limeCrete render for insulation purpose with lime over the top, or a thicker hemp lime mix…

Wood wool boards to me seem to be too much of a risk…

And as I understand if we can keep the walls dry, the rooms breathing and heat on it should feel warm…
Unlike the farmhouse we live and rent in currently down the road which is horrendous cold and damp, covered in cement outside and pink plaster inside, with awful cheap pvc windows replacing the single sashes, it’s a perfect example of damp mouldy house that needs saving, alas the landlords will not save it!

We also want to life the slate flagstones, carefully, and lay a limeCrete subfloor, foam glass etc etc with underfloor heating and then carefully relay the slate flags….

I KNOW it’s a shame to lift them… but I feel that the added benefits of underfloor heating to this period farmhouse wil help save it for years to come aswel as making it a viable place to live and grown a family.

My questions then:

1)
Internal wall insulation - to bother or not to bother ? Hempcrete, hemp/lime mix, or just 3 layers of lime and crack on.

2)
Outside: remove cement by hand? Brush off old lime, take out joints? Or…. Do we get the outside sandblasted ?

3)
Once cleared outside do we then re point in lime and lime wash?
Is that the correct term / thing to do?

There’s PLENTY more to see and questions to ask but I don’t want to overwhelm!
The loft has an interesting “room” in between the 2 main trusses that is all lath and plastered which makes me think why would they bother doing that unless it was a sleeping area for servants? House doesn’t seem grand enough to have servants! But it has a “back” kitchen , scullery, so maybe they did…
Today we just found a doorway in an upstairs wall that had been plastered over and could’ve led to an attic stair but now has the shower / bathroom on the other side of it… all very interesting

I think upstairs floorboards will need replacing… we want to mill locally oak welsh floorboards… could be great…. Originals are patched with plaster (?!!) in the holes and very rotten and soft with many bits replaced by random bits of wood

It’s a great (daunting) project! And advice will be great fully recieved!


Many thanks in advance

Welshy women

 

[WetWales]

Sorry!
I meant a thin layer of HEMP on the walls.. hempcrete … NOT limeCrete on the walls

purlins also rotten… chimney breast leaking and water running (albeit slowly) down chimney in loft…

Oh lots to do!!

 

[a twig]

Beautiful! Plenty on here have used wood wool and wood fibre without issue, but with walls that thick, if it were me, once they are dried out I wouldn’t be worried about IWI. If you have someone lined up to do the traditional lime plaster then crack on.

Outside, I’d just tidy up by hand to be honest, remove wrong materials and finishes, repairs with appropriate materials where needed, repoint with an NHL2 or NHL3.5 mortar depending on what stone the walls are constructed from then either limewash or a silicate exterior paint which would require less frequent renewal should see you right.

 

[aockenden]

1) After living through 3 winters in a 250 year-old Welsh stone cottage, we decided we needed some thermal improvement to our stone walls. Even though they are dry (having been stripped of cement and re-pointed in Lime almost 2 years ago now), they are still too cold and can experience condensation if our internal humidity is too high from cooking or whatever and the outside temp is too low. We definitely did NOT want to hide our stone walls behind any stud / battening system even if it was done with breathable materials, as I would still be paranoid of trapping damp back there (and you also lose the natural organic curves in the stone walls), so we decided on a granulated cork + hemp + lime plaster / internal render of 40mm thick applied in 2 coats directly onto the bare stone, followed by a lime + fine sand finishing coat. We are currently in the process of applying this to our first room, so I can’t report back on thermal improvements yet.

2) You seem to be under the impression that sandblasting could be an option for physically removing the external cement render / pointing. Unless it is VERY thin (a couple mm at most) this is unlikely to work. The typical approach is to hack and smash the cement render off the stone wall substrate using hammers, chisels, SDS impact drills etc. and then AFTERWARDS you sandblast the newly uncovered stone in order to clean it up of any old paint / mold/ limewash or whatnot in preparation for repointing or re-rendering in lime

3) Yes repointing in lime and limewashing is an appropriate approach externally, or the alternative is you render the entire wall in lime.

 

[a twig]

Oh and while you have all the plaster off the walls, get all your wiring done, nothing more depressing than seeing immaculate new lime plaster that you’ve just paid a professional asmall fortune to deliver being chased out a couple of months later by a club handed sparky who inevitably then splats Easifill in afterwards to cover their tracks.

Just be aware when lifting the stone floors they almost certainly won’t be calibrated (ie a standard thickness) and could range from 2” to 6” thick just across one stone, so re-using them may not be an option.

 

[CliffordPope]

Just be aware when lifting the stone floors they almost certainly won’t be calibrated (ie a standard thickness) and could range from 2” to 6” thick just across one stone, so re-using them may not be an option.

Slate must have been incredibly cheap in the old days, and the builders incredibly strong. I've come across floors that had stones at least 6" thick which I could barely drag, yet someone managed to pick up and level the top the top accurately. Yet I could split it easily with a chisel and create two slabs for the price of one, at half the weight.

 

[SimonNorthWales]

1) After living through 3 winters in a 250 year-old Welsh stone cottage, we decided we needed some thermal improvement to our stone walls. Even though they are dry (having been stripped of cement and re-pointed in Lime almost 2 years ago now), they are still too cold and can experience condensation if our internal humidity is too high from cooking or whatever and the outside temp is too low. We definitely did NOT want to hide our stone walls behind any stud / battening system even if it was done with breathable materials, as I would still be paranoid of trapping damp back there (and you also lose the natural organic curves in the stone walls), so we decided on a granulated cork + hemp + lime plaster / internal render of 40mm thick applied in 2 coats directly onto the bare stone, followed by a lime + fine sand finishing coat. We are currently in the process of applying this to our first room, so I can’t report back on thermal improvements yet.

2) You seem to be under the impression that sandblasting could be an option for physically removing the external cement render / pointing. Unless it is VERY thin (a couple mm at most) this is unlikely to work. The typical approach is to hack and smash the cement render off the stone wall substrate using hammers, chisels, SDS impact drills etc. and then AFTERWARDS you sandblast the newly uncovered stone in order to clean it up of any old paint / mold/ limewash or whatnot in preparation for repointing or re-rendering in lime

3) Yes repointing in lime and limewashing is an appropriate approach externally, or the alternative is you render the entire wall in lime.

Hows the work going Aockenden? Very interested to hear any feedback after a couple of months.

 

[aockenden]

Hows the work going Aockenden? Very interested to hear any feedback after a couple of months.

Hey it’s slow going but steady progress. We’ve got a second room almost fully base-coated (first rough coat of hemp+cork+lime, 2cm thick). Pic attached. I just bought an infrared temperature gun to check wall temps on our first room and it looks like we’re getting between 1.5 to 3 degrees Celsius improvement in wall surface temps from the base coat.

Plus when you put your left thumb on the insulated / rendered sections and put your right thumb on the bare stone there is a VERY noticeable difference in the perception of temperature on your thumb. I can’t exactly get it straight in my head if laser measured wall temps and a touch test represent exactly the same thing. I can definitely say touching with fingers makes the difference seem more like about 5-10 degrees, not just the 1.5 to 3 degree diff measured by the infrared thermometer. Would love people’s input on that.

And again, this is all just for the first 2cm thick insulating basecoat. There will be another 2 cm thick insulating coat made with finer insulating aggregates applied after this, so hopefully we see additional improvements from that.

 

[pandora_boite]

Hi Aockenden,
I am very interested in the insulated plaster that you have used. I would like to use this type of plaster to my solid brick walls. Please can you give a bit more detailed info about what base coats and layers you used. Did you use any particular brand of insulating plaster? There seem to be many different types out there so it would be know a bit more about the pros and cons of each one.

Any advice would be much appreciated.

 

[aockenden]

Hi Aockenden,
I am very interested in the insulated plaster that you have used. I would like to use this type of plaster to my solid brick walls. Please can you give a bit more detailed info about what base coats and layers you used. Did you use any particular brand of insulating plaster? There seem to be many different types out there so it would be know a bit more about the pros and cons of each one.

Any advice would be much appreciated.

Hey we mix our own using raw ingredients so I can’t advise on which brands to use.

Our full end-to-end process that we’ve settled on is as follows:

1. Hack off all cement render with SDS, getting back to bare stone (a fairly hard blue / grey stone, not sure exactly what kind)

2. Wet down joints and Repoint / dub-out in NHL 2 + sand (2.5:1 ratio by volume, dry NHL powder) and let cure for about a week or so. We might spray it down a couple times during this week to slow the drying

3. Mix 1.25 buckets cold lime putty (made with either hydrated or quicklime), 0.25 buckets NHL powder (whatever strength I’ve got on hand), 1 bucket of coarse hemp, 1 bucket of coarse granulated cork. Mix it with an electric paddle mixer slowly adding water until I get a really thick mix I can ball up into a sticky snowball. The power paddle mixer is absolutely worth the investment, as I mixed many batches in a wheelbarrow with a garden Hoe and it is very strenuous work.

4. Lightly damp down the stone wall and then ball up the mix in gloved hands and smear onto the wall at an avg thickness of 2 cm. We leave this first coat quite bumpy from finger indentations and deliberately don’t smooth it too much with a trowel or anything in order to keep a nice rough mechanical key for the second coat.

5. Let first base-coat dry for a month. We do not spray it at all as it dries very slowly on its own. If sections are still damp after a month we run a dehumidifier on low in the room. We heat and ventilate the room throughout the drying period.

6. Mix 1.25 buckets cold lime putty, 0.25 buckets NHL powder, 1 bucket of FINE hemp, 1 bucket of medium perlite. Mix with paddle mixer adding water until we get a slightly wetter mix than the first base coat.

7. Apply the second mix ontop of the dried first coat by smearing with gloved hands at an avg thickness of 2 cm again. Once the whole wall is coated, we smooth this coat out with a flexible plastic trowel to provide a smoother base for our final skim coat.

8. Let this second coat dry for a month. Same protocol for drying as the first coat.

9. We haven’t done this part yet but we are planning to do a final skim-coat with just fine sand and lime putty, finished with a fine-grained sponge float. Then paint with limewash or simple clay paint.

From one batch of about 30 liters of final mixed insulating lime render, we are getting about 1.5 square meters of coverage. That’s my best estimate anyways.

 

[aockenden]

Hey we mix our own using raw ingredients so I can’t advise on which brands to use.

Our full end-to-end process that we’ve settled on is as follows:

1. Hack off all cement render with SDS, getting back to bare stone (a fairly hard blue / grey stone, not sure exactly what kind)

2. Wet down joints and Repoint / dub-out in NHL 2 + sand (2.5:1 ratio by volume, dry NHL powder) and let cure for about a week or so. We might spray it down a couple times during this week to slow the drying

3. Mix 1.25 buckets cold lime putty (made with either hydrated or quicklime), 0.25 buckets NHL powder (whatever strength I’ve got on hand), 1 bucket of coarse hemp, 1 bucket of coarse granulated cork. Mix it with an electric paddle mixer slowly adding water until I get a really thick mix I can ball up into a sticky snowball. The power paddle mixer is absolutely worth the investment, as I mixed many batches in a wheelbarrow with a garden Hoe and it is very strenuous work.

4. Lightly damp down the stone wall and then ball up the mix in gloved hands and smear onto the wall at an avg thickness of 2 cm. We leave this first coat quite bumpy from finger indentations and deliberately don’t smooth it too much with a trowel or anything in order to keep a nice rough mechanical key for the second coat.

5. Let first base-coat dry for a month. We do not spray it at all as it dries very slowly on its own. If sections are still damp after a month we run a dehumidifier on low in the room. We heat and ventilate the room throughout the drying period.

6. Mix 1.25 buckets cold lime putty, 0.25 buckets NHL powder, 1 bucket of FINE hemp, 1 bucket of medium perlite. Mix with paddle mixer adding water until we get a slightly wetter mix than the first base coat.

7. Apply the second mix ontop of the dried first coat by smearing with gloved hands at an avg thickness of 2 cm again. Once the whole wall is coated, we smooth this coat out with a flexible plastic trowel to provide a smoother base for our final skim coat.

8. Let this second coat dry for a month. Same protocol for drying as the first coat.

9. We haven’t done this part yet but we are planning to do a final skim-coat with just fine sand and lime putty, finished with a fine-grained sponge float. Then paint with limewash or simple clay paint.

From one batch of about 30 liters of final mixed insulating lime render, we are getting about 1.5 square meters of coverage. That’s my best estimate anyways.

Here’s the section of stone wall we did today (a section behind a built-in wardrobe). Felt really good to get the cement off the wall back there and get the stone coated with lime while simultaneously improving the wall temp with some insulation value. I’m pretty confident we’ll have no condensation / mold issues behind this wardrobe in the years to come.

 

[pandora_boite]

Thanks for the detailed info. Your project looks great. Good luck.

 

[WetWales]

Sorry for slow reply and Thanks for the detail @aockenden it looks so good what you’re doing! I’m still dithering about vest choices internally, I wanted to go with a full Hempcrete layer then lime but proving difficult to find anyone to do the Hempcrete so thinking of lime / cork mix.

Does anyone know if a lime / cork mix or lime / cork & hemp mix is much different in terms of insulation value? I’d imagine more cork is more expensive but from what I’ve read less chance of mildew / mould with cork?

Because the house has been empty so long and is so damp, I’m worried about the mould whilst it dries!

But… I think once the limecrete floor is down and then once the UFH and heating is working it should be warm and I hope to do the floors first before the walls go on!

 

[WetWales]

work slowed right down as we got sick so much lately! (toddlers) but we’ve had scaffolding up now and I’ve been up on to take a closer look at the chimneys

Purlins are rotten inside so we knew it’s long been a problem, heavy rain sees the chimney breast running inside and dripping onto bedroom floor!

Common sense tells me the problem is because the lead work is not actually into the chimney, merely butted against and then the cement lip over the top that I assume they thought the water couldn’t get behind!!

Will installing proper lead work into the chimney the right way, removing cement and replacing with lime, should solve it all?

pics attached for enjoyment!!

 

[aockenden]

Sorry for slow reply and Thanks for the detail @aockenden it looks so good what you’re doing! I’m still dithering about vest choices internally, I wanted to go with a full Hempcrete layer then lime but proving difficult to find anyone to do the Hempcrete so thinking of lime / cork mix.

Does anyone know if a lime / cork mix or lime / cork & hemp mix is much different in terms of insulation value? I’d imagine more cork is more expensive but from what I’ve read less chance of mildew / mould with cork?

Because the house has been empty so long and is so damp, I’m worried about the mould whilst it dries!

But… I think once the limecrete floor is down and then once the UFH and heating is working it should be warm and I hope to do the floors first before the walls go on!

When you say you’re dithering about wether you should go with internal hempcrete on the walls, I assume you’re referring to the “shuttering” / built forms which are then compressed or packed in with a mix of hemp + smaller amounts of lime (just enough to coat the hemp)?

If that’s what you meant then yeah we chose to avoid that option so we didn’t lose so much interior space, didn’t end up with flat modern-looking walls, and because of mold risk with the very hemp-heavy thick layer not drying out quick enough and having less lime in the mix to naturally combat the mold spores. It made me nervous.

My understanding is cork is a better insulator than hemp. We still use half-cork and half-hemp in our insulating plaster / render though as we like the longer fibers of the hemp and hemp is much cheaper than granulated cork. We only apply in 20mm thick coats (and give a full month to dry in between coats) so we’re not worried about mold from either the hemp or cork.

 

[WetWales]

Yea that’s what they said they would do, shuttering it on then pouring the Hempcrete in, or use ready made hemp blocks from Europe attached with wires then back filled the voids… we didn’t like the sound of either for the reasons you mention above, space and flat wall…they said they could skim the wall first so they wouldn’t have to back fill, but still end up with 80mm hemp blocks then lime… space is limited as rooms are small!

I originally thought that Hempcrete was spayed on but apparently not many people gave that kind of equipment so I’m back to thinking of lime /cork mix!
I’ve just read your posts of another thread where you go into detail, very interesting and kudos for doing it yourself!

 

[aockenden]

Yea that’s what they said they would do, shuttering it on then pouring the Hempcrete in, or use ready made hemp blocks from Europe attached with wires then back filled the voids… we didn’t like the sound of either for the reasons you mention above, space and flat wall…they said they could skim the wall first so they wouldn’t have to back fill, but still end up with 80mm hemp blocks then lime… space is limited as rooms are small!

I originally thought that Hempcrete was spayed on but apparently not many people gave that kind of equipment so I’m back to thinking of lime /cork mix!
I’ve just read your posts of another thread where you go into detail, very interesting and kudos for doing it yourself!

Makes sense, many decisions with different benefits and drawbacks as usual!

Good luck with it, hope my info gives you some food for thought.

 

[Lacan07]

work slowed right down as we got sick so much lately! (toddlers) but we’ve had scaffolding up now and I’ve been up on to take a closer look at the chimneys

Purlins are rotten inside so we knew it’s long been a problem, heavy rain sees the chimney breast running inside and dripping onto bedroom floor!

Common sense tells me the problem is because the lead work is not actually into the chimney, merely butted against and then the cement lip over the top that I assume they thought the water couldn’t get behind!!

Will installing proper lead work into the chimney the right way, removing cement and replacing with lime, should solve it all?

pics attached for enjoyment!!

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Yeah this chimney definitely needs some attention lol, new lead, remove any cement and repoint, and I'd hack that top off and re-flaunch.

 

[WetWales]

Thanks Lacan! Yes it does doesn’t it! Although shame to disturb the trees that are growing there haha
Do you think it’s better to do it all in lime including the flaunching ?
The local roofer we’re using hasn’t used lime before although he’s keen to learn about using it and has just started learning about the whole old house breathable lime thing which is cool because the more youngsters that learn for the future the better!

He said he wants to use a cement lime mix tho… but I think even that will hold moisture where it’s not wanted…

Or are flaunchings ok in cement as they’re not really wicking moisture to anywhere just sitting there?!

I’m new to chimneys so googling flaunching and all the meanings

Thanks for the comments!

 

[Lacan07]

Thanks Lacan! Yes it does doesn’t it! Although shame to disturb the trees that are growing there haha
Do you think it’s better to do it all in lime including the flaunching ?
The local roofer we’re using hasn’t used lime before although he’s keen to learn about using it and has just started learning about the whole old house breathable lime thing which is cool because the more youngsters that learn for the future the better!

He said he wants to use a cement lime mix tho… but I think even that will hold moisture where it’s not wanted…

Or are flaunchings ok in cement as they’re not really wicking moisture to anywhere just sitting there?!

I’m new to chimneys so googling flaunching and all the meanings

Thanks for the comments!

When it comes to pointing / flaunching chimneys many people have differing opinions about what to use. You certainly need a stronger material as a stack takes the worst of the weather and wind. Some roofers do indeed chuck a bit of hydrated lime powder into their cement mix which quite frankly will add nothing to breathability.

Its important to note that your chimney appears to be stone (of which I'm no expert) and not soft red brick as if often the case with old houses. Generally for chimneys of soft red brick I think a good compromise is an NHL 3.5 or 5 for the pointing and an NHL 5 for the flaunching. NHL is a recent addition to the lime family, the traditionalists don't like it because its often known to go off 'harder' than its grade which kind of makes it perfect for a chimney as its breathable too. This is whats recommended in the Haynes Period Property manual (the first book on old houses I ever purchased). Putty based lime might be considered too fragile for pointing a chimney and certainly flaunching. I can certainly understand why some people and roofers want to use cement but the problem is its prone to cracking which then allows water to penetrate which then cannot easily escape. NHL comes in powder form and is easy to knock with water, Spring is a good time to doing this kind of work.