Insulating a pebbledash solid wall and damp concerns

[Ben Weston]

35 minutes ago, Roger440 said:

 

Im suggesting you have a read of the links i posted. I could write it all myself, but to be honest, my attempt would likely be half arsed.

 

Ive no idea why you think im "passive aggresive"????

 

Have a read of some useful info IS my advice.

 

Not sure why i bothered now...........................

 

Roger, you've got me confused with saveasteading. You haven't posted any links in response to me and I've taken onboard the advice you've given me.

 

I've read a TON of information. If your advice is "read some useful info", perhaps a forum isn't the right place for you.

 

There's always one.

Edited February 5, 2022 by Ben Weston

[Iceverge]

5 hours ago, Ben Weston said:

Thanks! We're not currently living in the house. It's being stripped back to only the outer 3 walls - new roofs, new doors, new windows, new floors, etc. The disruption and challenges of marrying it up with the extension are moot. The extension design isn't really a concern to be honest: we're actually going to build that first, marry it up with the existing house and 'do' the original house last.

 

 

The more I read the more I'm thinking "bulldozer renovation time."

 

Unless you have a specific sentimental attachment or its of particular architecture or historical merit and you are willing to throw cash at it hand over fist. 

 

I don't like knocking down old stuff on principal but in this case it'll be unrecognisable anyway with EWI. 

 

Save yourself years of heartbreak, a ton of VAT and demolish. 

 

 

[Ben Weston]

4 minutes ago, Iceverge said:

 

 

The more I read the more I'm thinking "bulldozer renovation time."

 

Unless you have a specific sentimental attachment or its of particular architecture or historical merit and you are willing to throw cash at it hand over fist. 

 

I don't like knocking down old stuff on principal but in this case it'll be unrecognisable anyway with EWI. 

 

Save yourself years of heartbreak, a ton of VAT and demolish. 

 

 

 

I've had that discussion again with my wife this evening. 

 

I'd knock it down, she's sentimentally attached to keeping some of the original structure. 

 

Unfortunately, our planning was approved in January after 4 months and, with 3 kids in tow and currently living in a static home, neither of us fancy going to the back of the queue again for a new planning application for demolition. The original intention was to keep the original house – this has unfortunately transpired to retain less and less as the process has gone on.

Edited February 5, 2022 by Ben Weston

[Iceverge]

Does she not like money? 

 

Or warmth................?

[Ben Weston]

1 minute ago, Iceverge said:

Does she not like money? 

 

Or warmth................?

 

Just edited my comment above to explain why but yes, it's a tricky one for me to navigate.

[Iceverge]

If you're happy with the plans just reapply for exactly the same design.

 

In the meantime you can crack on with the extension. Then tie in the new/old house when the time comes. 

 

Even if you don't you'll save 4 months in the build program. 

[Ben Weston]

18 minutes ago, Iceverge said:

If you're happy with the plans just reapply for exactly the same design.

 

In the meantime you can crack on with the extension. Then tie in the new/old house when the time comes. 

 

Even if you don't you'll save 4 months in the build program. 

 

I've asked the question of the architect again. It was my understanding this approach wouldn't be possible but I could very well be wrong. I most often am.

[SimonD]

5 hours ago, Ben Weston said:

I want to go back and suggest that the whole house (old and new) are covered in the same external insulation system to ensure continuity.

 

FWIW that's exactly what I did with my infill extension. Photo attached after basecoat applied with no difference between the parts of the house. The ideal thing about this is that you can then design the house details such as window reveals etc. to fit the design 'theme' of the house. In my photo you'll see that my windows have been moved out from the walls on the house and sit in the ewi to reduce thermal bridging around the frames. The negative side of this is that the depth of the reveals meant I had to make myself a bespoke reveal detail because the normal window/corner beads/ and reveal boards would not fit within such shallow reveals.  As you'll see from the image I also curved my reveals as I didn't want the square sharp corners typically found on new ewi. This is where you ideally need someone with experience working with ewi as they'll be able to guide you with the detailing, something you don't want to find out about when it's too late and the renderers are on site.

 

5 hours ago, Ben Weston said:

That said, the suggestion seems all wrong to me.

 

Your architect is merely suggesting what is a more mainstream approach and using the typical system sold by Weber which will be installed on a lot of houses across the UK. He/she may also be reflecting what you already mentioned as a lack of understanding of ewi systems. Like you, it's not the direction I would choose to take although if installed and detailed properly it will probably last the lifetime of the building providing it's maintained correctly too.

 

There's nothing wrong with asking your architect to reconsider and include the works for removing the pebbledash and alternative buildup, but what I would personally strongly recommend is that based on your personal preference of materials you find and then use a complete ewi system and avoid selecting individual layers yourself that aren't part of the system. As mentioned before, get the manufacturer's technical department to complete a condensation risk analysis to demonstrate suitability of the buildup. You can also play with online tools like ubakus.com to get a feel for what you want.

 

As a side note, please do remember to remove the pebbledash before you remove the roof and gut the house - old walls can become terribly unstable when you take the load off them and you don't want to be hammering the existing render off then! ?

 

You're clearly doing your research so I'm sure you'll settle of the right solution for you. Good luck with it.

 

[SimonD]

I do have to say @Iceverge's suggestion is spot on.

 

Having never taken on the scale of building work we're doing, we sought advice and received it from several professionals; surveyor, architects (2), and an architectural technologist. All of them said, don't demolish, extend instead (partly due to the planners). We followed this advice and the architect supposedly designed all the new stuff to keep almost the entire bungalow - we were only supposed to be adding a small infill extension, raising the roof and adding a 1st floor. Yeah, right. When I started demolishing, it just went on and on and on and got to a point where so little was left that I seriously think all the advice we recieved was totally wrong and we should have demolished but by that time is was just too late. It's be a pain to say the least and has ended up taking far longer than it needed to. I think our architect ran away and hid smewhere because he knew he might end up in the new pad foundations otherwise, or hanging from the new steels ? I did tell him so when he finally came for a visit!

 

Sit down and have a really careful think...

 

Here's what was left our our bungalow including the day the new steels went in. And you can see how much I had to repair even of the existing walls. I've learnt a lot, that's for sure!

 

 

 

 

[saveasteading]

5 hours ago, Roger440 said:

Where on earth did you read that?

The wall is 600mm thick granite, so any form of dpc is out of the question.

I will look at your references with interest.

[saveasteading]

5 hours ago, Roger440 said:

you would do well to aquaint yourself with these:

OK done that. It is a bit of a rant unfortunately, and calling surveyors idiots isn't  measured or encouraging.

 

However, I am perfectly happy to hear advice that shows we do not need to spend money and time on the low level tanking currently intended. btw we got this idea / solution from a blog elsewhere, for a similar farm steading.

I considered the bottom metre being tanked as reasonable (an extension of the dpm) and the wall can still breathe outwards and will be unsealed for the remainder of the wall height.

However the drawing I copied doesn't show tanking either, so perhaps this is not proven.

 

Our walls are currently wetter inside than out, as the air and wind evaporate water on the outer faces.

When the gutters are repaired the wetness will reduce and only driving rain will wet the walls, and obviously will run down an make the bottoms wetter.

Rising damp is impossible as our footings are on porous sand.

 

Advice also welcome on ventilating the wall. The cross section I coped here shows ventilation through the wall, to pass up the new void between stone and new inner lining. That will suck a lot of heat out of the building so seems unwise. But I know from another Buildhub member that  there are cases of Officers insisting on this.

[Adsibob]

10 hours ago, SimonD said:

Having never taken on the scale of building work we're doing, we sought advice and received it from several professionals; surveyor, architects (2), and an architectural technologist. All of them said, don't demolish, extend instead (partly due to the planners). We followed this advice and the architect supposedly designed all the new stuff to keep almost the entire bungalow - we were only supposed to be adding a small infill extension, raising the roof and adding a 1st floor. Yeah, right. When I started demolishing, it just went on and on and on and got to a point where so little was left that I seriously think all the advice we recieved was totally wrong and we should have demolished but by that time is was just too late.

This is very similar to my experience. Our “renovavation” started 14 months ago and is still not finished. With some luck and a fair wind, we might be finished in the next 8 weeks or so. I suspect there will be plenty of snagging so it won’t be “finished” till later this year.  That will make the project the best part of a year and a half and I really do think it would have been much faster to knock down and start again. I’m not sure it would have been cheaper though. Presumably the insurance requirements of knocking down a semi detached house are much higher, as well as the costs of temporary props to support the adjacent house. And then there would be more costs involved in complying with regs for a new build. Of course, I would have ended up with a warmer house, so it pruebo would have been worth it.

Edited February 6, 2022 by Adsibob

[Roger440]

9 hours ago, saveasteading said:

The wall is 600mm thick granite, so any form of dpc is out of the question.

I will look at your references with interest.

 

Yes, sadly it does come across a bit "ranty". However, pretty much everything is actually correct. He just could have said it differently!

 

Going back to the beginning, the actual question is, why is the wall wet? Not "how can i cover it up?"

 

Yes, thats what often happens. But long term this cant end well. Regardless of the surface finish on the wall, its almost certainly built with some sort of lime/earth type mortar. If permanently wet it will decay. The stones be granite will be fine in this case.

 

What your picture shows is what happens when the water is trapped in the wall. Indeed, it exactly what was happening to mine. Mines is a very permeable lightweight brick with traditional lime mortar and no DPC.

 

When i bought it, it was plaster with gypsum on the side, the floor was concrete over a plastic sheet. In some places the ground level outside was higher than inside. There were 3 hearths one on top of the other, and the chimney uncapped. The oustside is rendered. Mostly in lime but patched in cement, but painbted with a modern masonary paint. The walls were wet, and had been for a long time. There were 3 hearths one on top of the other, and the chimney uncapped. The socket back boxes , circa 500mm up from level had rotted away entirely as a result. Of you drilled a hole in the wall, all that came out was a wet slurry. Humidity in that room was normally over 90%. Oh, and it had had a chemical DPC added at some point.

 

Percieved wisdom was tank it internally. Problem with that, is you are trating the symptom, not the problem. A good analogy, is, if you washed your clothes and put them in a plastic bag and hung them on a washing line, what do you think will happen? 

 

Thats what you are doing by tanking it. The moisture will simply go ever futher up the wall.

 

So i set about sorting all the problems in mentioned, speeded up by the fact we had a flood, so we had to strip out carpets etc.

 

Prior to the flood i had already sorted out the ground levels outside, in particular the gable end wall. The chimney was capped with a vented cap, so in no longer rained in the fire place. I had to repoint the brick work below the render, all done in lime, and the cement pointing removed.

 

After the flood, plaster came off first which allowed me to easily see what was wet and how far up. Wasnt a metre but over 500mm in places. The drying out started straight away. Within a month, 90% showed no visible damp apart from the 1st visible course above the floor. Then we pulled up the concrete floor.

 

The ground was wet under the DPC, as you would expect. I then left it for about 8 months. During that time its completey dried out. Evertyhing, walls, the dirt floor, even the limestone foundation stones. Some of the mortar fell out as it had disintegrated through being wet. Humidity, with NO floor, sits around 70-75%

 

Its now dry. No damp in the walls. Simply becuase it can now function the way it did before it was built. Ie, moisture can arrive and evaporate. Yes, accepted it does require a degree of ventilation, and yes, that will ulitmately limit the level of thermal efficency you can apply. But a dry house feels warm, a wet house cold.

 

2 weeks ago we finally got the floor laid. Foamed glass as the insulating & foundation layer, lime screed over the top. The principle here is to insulate, but allow moisture to pass through if it needs too. Water were it exist under there cannot "wick up" the foamed glass.

 

I will admit, when i started this, i was sceptical that this was going to resolve the issues. Frankly, its staggering the difference and speed at which that occurred., though the nature of the bricks involved probably helped the speed.

 

From an engineering perspective it makes perfect sense however. Sadly, most builders are not engineers. As many on this forum will testify, most still dont grasp the basics of how to install insulation, dew points etc. Its no surprise inappropiate solutions are applied frequently. Because im sad, im always looking at old houses, and shaking my head in disbelief at the things that people doo.

 

Back to mine. To finish off, limestone tiles on a lime based adhesive. Lime plaster with a suitable natural paint over. And this is they key. Every layer needs to be breathable. Everyone clains there products are breathable. They are not, at least not to a level that is remotely useful in these applications.

 

Ask for the breathability data. What is the actual number? Take that for a lime render for example. Then compare to masonary paint, cement, gypsum etc. Tells you everything you need to know.

 

My rather short post originally should really read, fix the problem, not the solution. There's a reason, probably several, why your wall is wet. Your picture is not it. Its just a reflection on the state of your wall. Indeed, a reflection of mine. Critically it shows everything pushing the moisture TOWARDS the wall. That IS the actual problem i had. Caused by inappropiate materials and methods.

 

 

 

 

Edited February 6, 2022 by Roger440

[Ben Weston]

All really interesting information yet again, thanks all.

 

@SimonD and @Adsibob – On demolishing and starting again, your experiences sounds very similar to ours. We started this process intending to retain and improve the old cottage, and add an extension. As we've progressed, we've realised floors need digging up, first floor levels need raising, roof needs completely scrapping and starting again, etc, etc. As we've gone on, we've got to the point where, while working on the detailed plans, we've ended up keeping just the outer 3 walls of the original cottage. This is contrary to all the advice we'd also had initially and is frustrating as, if we'd known we'd knock it down from the beginning, the new design we have would likely have been different. I have asked the question again as, although it's slightly more expensive to demolish and build again, it seems to work out a bit cheaper/the same once we factor in the VAT reclaim (if we can get it). I think it would be quicker too.

 

I appreciate all the advice I've had. It may very well be that we cut our losses at this stage and forge ahead with the plan to keep those three walls and use EWI around the whole building. I'm mindful of the timeframe and cost and that'll determine the decision ultimately. I'm confident we'll have a well-insulated house either way (roof and floors will have identical U values, walls will be about 0.1 less with cavity obviously). As I say, my wife and I – and three young children! – have been living in a static home on-site since August last year and we've not laid a brick yet. I'm not up for making this any longer than it needs to be!

 

Incidentally, I downloaded BuildDesk and used the trial to run a condensation / heat loss analysis. It was extremely helpful. Interestingly, where we live and the way the house is currently constructed, there is apparently no interstitial condensation risk. Would explain why we have no damp. Tried modelling with rockwool EWI with lime render, as well as Weber's system, and both still had no condensation risk. Obviously both offered significantly lower U values. I'll take it with a pinch of salt but it was very helpful.

Edited February 6, 2022 by Ben Weston

[SimonD]

2 minutes ago, Ben Weston said:

have been living in a static home on-site since August last year and we've not laid a brick yet. I'm not up for making this any longer than it needs to be!

 

Try 3 years and still counting ! ??? Only two boys and I've done everything myself mind you. Not too far off now. As the labour is entirely mine, we're still below that VAT/build cost advantage especially once I take into account the estimated costs of demolition, new foundations etc.

[SimonD]

1 hour ago, Adsibob said:

I’m not sure it would have been cheaper though.

 

As it currently stands for us, we're ahead on financial costs, but way overdrawn on headaches, PIAs, and time... I really do want my life back. ?

[Ben Weston]

1 minute ago, SimonD said:

 

Try 3 years and still counting ! ??? Only two boys and I've done everything myself mind you. Not too far off now. As the labour is entirely mine, we're still below that VAT/build cost advantage especially once I take into account the estimated costs of demolition, new foundations etc.

 

Well done! What an achievement. It's somewhat reassuring to know we're not the only mad ones ? 

 

Although I'll be undertaking most of the finishing and "donkey work", we'd intended to pay for bricklayers and carpenters to get the shell up and watertight. I can do the foundations, drains, floors, etc myself but I obviously can't lay bricks as fast as a bricklayer and would rather leave the roof to a carpenter. 

 

Another morning on Excel looking at costs of the two options again for me!

[saveasteading]

On 05/02/2022 at 19:34, Roger440 said:

you would do well to acquaint yourself with these:

 

Returning to this supposedly expert study... When we took on this project I assumed that there would be any number of how to do it/ advice /even stated methods in the regulations.

Far from it, and it seems that different councils and inspectors even have their own (differing) expectations

 

Currently I propose to avoid any drilling of holes through the 600mm of wall,  to maintain the physical and thermal barrier,  then apply 1m of bitumen sheet to the bottom metre inside, and leave the remaining 2-2.5m exposed. then a 50mm air gap. Inside this a timber frame filled with insulation, and sealed on the outer side by a breathable membrane, and the inside (before boarding) with an air-tight membrane.

AS far as I am aware this is not exactly specified anywhere else, but nothing else is either.

The air gap will be continuous to the roof sarking where it can breathe.

Where does moisture come from? Not a lot up from the ground as it is granite and dampness doesn't rise far (as discussed earlier).

Roof and gutters will carry away 99% of rain that currently dribbles down the walls. the ground is pure sand so it won't be wet around. pointing will be repaired or tided.

So the wet is only from driving rain (which will run down the wall) and general moisture. Before any of that gets through 600mm it should be dried by the air and wind.

 

Any and all advice and speculation welcome.

 

[saveasteading]

Does silence mean 1. Nobody knows. 2 Boring question. 3. I've told you already, are you not listening? 4. Give it your best shot and report back ?

 

btw, in the doc referred to by Roger440, they show a canal wall as proof that rising damp does not exist. 

This wall will be built in very high quality engineering bricks with waterproof mortar, so it isn't the best argument.

If they were normal bricks they would be wet for a few courses above the water, and probably green with algae.

 

Roger440, any further thoughts on my pragmatic addition of the internal liner to 1m?

 

that is a downpipe btw, not external cladding.

[Simplysimon]

yes this will allow ventilation up the internal face, but what is it going to do for the thermal properties? the majority of people on here with dot and dap complain about the tent effect.

 

On 06/02/2022 at 10:13, Roger440 said:

Thats what you are doing by tanking it. The moisture will simply go ever futher up the wall.

no it won't, capillarity will only take the moisture up to approx 1.2m

[Cpd]

On 06/02/2022 at 01:10, saveasteading said:

I considered the bottom metre being tanked as reasonable (an extension of the dpm) and the wall can still breathe outwards and will be unsealed for the remainder of the wall height.

I have been mulling this over for some time as I also have an old stone building that I am renovating, no DPM in the wall but DPM coming up from the floor I laid, 5 years ago I had intended to extend the floor DPM one meter up the  wall on the inside to prevent any water ingress but am concerned this will attract condensation…. The project stalled 5 years ago so nothing has happened and last I looked it was actually now very dry……. I thought about swapping out the black plastic for something like building wrap / roof membrane but am now just thinking that if it’s dry I should not over think it and just ignore it ….. build the stud work, insulate between and over the studs, vcl and then board it out…… 

 

my own house has a vented void between the inside stone wall and stud work with internal insulation over the top, the stone walls are damp behind the studwork but it’s vented and is still standing over 100 years  later so I just left it alone and moved onto the next job….. 

 

i think you need to eliminate and water ingress from above, clear anything around the outside of the building that may be stopping air flow and scrape away damp earth and vegetation to clean subsoil / sand and see what happens, i did all this to my site as well as power washing both the outside and inside of the walls to leave very clean stone and no loose mortar, i then repointed and left it for 5 years…..(not intended) but it’s all now very dry. 
 

my walls are  the typical outside stone, rubble core and inside stone - walls about 6-700mm gables 1000mm 

[Roger440]

1 hour ago, Simplysimon said:

yes this will allow ventilation up the internal face, but what is it going to do for the thermal properties? the majority of people on here with dot and dap complain about the tent effect.

 

no it won't, capillarity will only take the moisture up to approx 1.2m

 

Well, yes. But the wall will be wet forever.

[Simplysimon]

43 minutes ago, Roger440 said:

 

Well, yes. But the wall will be wet forever.

not arguing that point, ok, i will, only if the cause can't be rectified, just some of the statements ? and pointing out issues with a 'remedy'

[SimonD]

17 hours ago, saveasteading said:

Does silence mean 1. Nobody knows. 2 Boring question. 3. I've told you already, are you not listening? 4. Give it your best shot and report back ?

 

None of the above, just busy building and sorting out some of my own building related questions ? But you may not have been asking me..

 

My initial sense is to question the purpose of the bitumen and whether it is really needed given the ventilation and cavity. Also, is the ventilation between the suspended floor and iwi cavity a continuous gap along the junction, similarly at the ceiling?

 

 

[Roger440]

On 07/02/2022 at 18:59, saveasteading said:

Does silence mean 1. Nobody knows. 2 Boring question. 3. I've told you already, are you not listening? 4. Give it your best shot and report back ?

 

btw, in the doc referred to by Roger440, they show a canal wall as proof that rising damp does not exist. 

This wall will be built in very high quality engineering bricks with waterproof mortar, so it isn't the best argument.

If they were normal bricks they would be wet for a few courses above the water, and probably green with algae.

 

Roger440, any further thoughts on my pragmatic addition of the internal liner to 1m?

 

that is a downpipe btw, not external cladding.

 

I missed this post.

 

My answer is, your wall is wet. It shouldnt be. So fixing the wet issue is fixing the problem rather than applying a cover up. Will that be easy? Possibly not. Im not sure what i did was easy, but it was logical and highly effective.

 

I certainly woudnt run a liner up the wall. Sure, if its a quick job to tart it up and scarper. But long term, you will make the problem worse as you have removed an evaporation path. Assuming its lime mortar, it will decay and break down. How quickly? who knows.

 

I know im an outlier compared to most of the building trade, but im firmly in the fix it once, fix it right camp. The answer to your opening line is number 3.