Things you've always wanted to know......

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Johnny Byrne's Boots
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Re: Things you've always wanted to know......

Post by Johnny Byrne's Boots »

view from the shires wrote: £7000 according to someone who had one on their dog.

.............
Ouch!
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Re: Things you've always wanted to know......

Post by hammerdivone »

view from the shires wrote:Current thinking is 50/50 whether a damp course is required or not as there is no evidence of capillary action up exterior walls.

From the evidence on my pond and filter house walls I would say that it isn't required. The filter house frequently has an inch of water inside due to a temporary roof and there is no damp rising up the walls.
Sorry but this is bollox. I've spent many years as a building surveyor investigating and remedying the issues of rising damp.

It does depend on the type of bricks used of course as some are more porous than others. In older properties where a cavity exists, from the 1920's onwards generally, there is often at the bottom of the cavity rubble and snots from the pointing, breaching the gap between the interior and exterior leafs. These early cavity walls did not have a vertical DPC (some didn't have a horizontal one either) or engineering bricks below ground level, which meant any build of moisture externally could easily transfer to the inner leaf. The inner leaf being finished with plaster which is much more absorbent than the brick, would then suck the water through and it would rise up the wall upto a metre in height.

BRE Research tells you all you need to know, and is summarised in these links https://www.designingbuildings.co.uk/wi ... t_(DG_245)
https://www.designingbuildings.co.uk/wi ... course_DPC
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Re: Things you've always wanted to know......

Post by Greatest Cockney Rip Off »

hammerdivone wrote:It does depend on the type of bricks used of course as some are more porous than others. In older properties where a cavity exists, from the 1920's onwards generally
Although you're right on the dates, you'd be hard pushed to find cavity walls on buildings (especially domestic) dating from before the 1950s. From my bricklaying days, I can't ever recall seeing or working on a cavity wall building dating from before the 50s. I still recall the advent of using Rockwool and polystyrene sheets within the cavity for insulation.
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Re: Things you've always wanted to know......

Post by Johnny Byrne's Boots »

My house was built around 1927 and has solid brick walls, no cavity. It also has a chemical DPC, not a rubber membrane type.
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view from the shires
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Re: Things you've always wanted to know......

Post by view from the shires »

hammerdivone,

I agree it depends totally on the bricks. A very specific make-up is required for capillary action to take place. The easiest way to test is stand a brick in water and see how long it takes for the water to rise up it. I have only used a limited number of bricks and blocks, but they all drain downwards not upwards I do concede it is not a representative sample. I have not plastered any of the walls I have built either, so that may also be a factor.
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Re: Things you've always wanted to know......

Post by Greatest Cockney Rip Off »

Johnny Byrne's Boots wrote:My house was built around 1927 and has solid brick walls, no cavity. It also has a chemical DPC, not a rubber membrane type.
You wouldn't have got a rubber membrane as a DPC on a house dating from then. The chemical DPC I'm assuming would have been done by a damp proofing company - you can tell by holes drilled at regular intervals and filled with cement running around the building. Sometimes houses from the 1920s and earlier had a course of slate, used as a damp proof membrane but again, these are rare.
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Re: Things you've always wanted to know......

Post by Johnny Byrne's Boots »

Yep. it's got a series of filled holes all round it.

How long do they last?
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Re: Things you've always wanted to know......

Post by hammerdivone »

GCRO - I used to own a semi-detached house in Guildford dating back to the early 1900's and that had a cavity wall, no cavity ties mind which could have been interesting. I have generally seen it commonly used from the 1930s onwards though.

As an aside, the issue with the earlier cavities is often that they used very few cavity ties and these were usually made of poor quality galvanised steel which eventually rotted away meaning a lack of stability between the two leafs.

Shires - I think the Building Research Establishment has done a few more tests than you tbh and I am struggling to understand how bricks sat in water drain downwards?

The simple answer is, the denser the brick the less the capillary action hence why engineering bricks are used below ground level.

JBB - When you bought the house the guarantee should have been passed over to you and would probably have been for between 20 - 30 years, although probably not worth the paper it's printed on.

A chemical DPC is not a good as physical DPC for many reasons, and in all honesty we have no idea how long they should last. They have been used for around 30 years or so now and there doesn't seem to be much data around failures, so your guess is as good as anyones.
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Re: Things you've always wanted to know......

Post by Johnny Byrne's Boots »

Thanks. We did get some paperwork from the previous owner, we've been in it now for twenty three years so I fully expect to be ripped off in the not too distant future.
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Re: Things you've always wanted to know......

Post by hammerdivone »

Johnny Byrne's Boots wrote:Thanks. We did get some paperwork from the previous owner, we've been in it now for twenty three years so I fully expect to be ripped off in the not too distant future.
I wouldn't worry too much, there doesn't seem to be any evidence of sudden failure, and if it had been done by cowboys you would have known by now.
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Re: Things you've always wanted to know......

Post by Johnny Byrne's Boots »

:thup:
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Re: Things you've always wanted to know......

Post by Greatest Cockney Rip Off »

To be honest JBB you could do it yourself. All you need to is hire a hand pump and buy the silicon soloution they use. Then just drill out the holes, give it a couple of squirts in the hole (ooeerr!), wait til dry and them make good with some mortar.
Don't do what I did. Was drilling through what looked to be a 9inch (double skin) partition wall, only to discover from the irate homeowner next door that it was 4inch (single skin). I ended up injecting silicon damp proofing all over her nice beige carpets. Livid wasn't the word. If she could have killed me I'm sure she would have. Cost the company a lot of money too! :oops:
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Re: Things you've always wanted to know......

Post by Monkeybubbles »

Greatest Cockney Rip Off wrote:I ended up injecting silicon damp proofing all over her nice beige carpets.
Deserves a thread of its own.
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Re: Things you've always wanted to know......

Post by Johnny Byrne's Boots »

:lol:

I think I'll leave well alone. I know my limits.
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Re: Things you've always wanted to know......

Post by view from the shires »

How does the damp from rain drain down through a damp course membrane?

HDO,

I had bricks and blocks sat in water in an unfinished pond (standard bricks, 7n dense concrete blocks and Bradstone type bricks / blocks). They stayed wet at the bottom and the water did not rise up them. Any rain drained downwards. I also have a stream that runs through a garden wall to a sump the other side. Until I sealed the bricks with G4 water seeped straight through them, but did not climb the wall.

I have followed the links and the published date is 1997 & 2007 for various articles. The first recorded report that rising damp was a myth was published in 2008 (I had to google it). Since then the theory has been gaining momentum. I understand the science for why it doesn't exist, but not for how it occurs. This doesn't necessarily mean that I am right, just that I am inclined to believe that it is not as common as originally thought.

Your comments on the volume of moisture expelled at night is really insightful. We are now looking for a second dehumidifier for our bedroom. We have one downstairs, as we have a marine tank and this is taking 5 litres of water out of the air a day. With this amount of moisture inside buildings surely this is a major contributor to damp in houses?
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Re: Things you've always wanted to know......

Post by hammerdivone »

view from the shires wrote:How does the damp from rain drain down through a damp course membrane?

It doesn't. Unless we had a serious monsoon period where the brickwork was completely saturated it wouldn't cause any problem unless there's breach of cavity

HDO,

I had bricks and blocks sat in water in an unfinished pond (standard bricks, 7n dense concrete blocks and Bradstone type bricks / blocks). They stayed wet at the bottom and the water did not rise up them. Any rain drained downwards.
Capillary action rising up through bricks can takes months/years before any effect is seen. Do you mean water that was on the top of the brick drained down through it? If so then by definition if water can drain through a brick, it can be drawn up as well, although nowhere near as quickly

I also have a stream that runs through a garden wall to a sump the other side. Until I sealed the bricks with G4 water seeped straight through them, but did not climb the wall.

And this is exactly what can happen with house brick walls. You see the term rising damp is a slight misnomer. The damp penetrates the brickwork and if the cavity is breached through rubble or snots the water will seep through that into the inner leaf. Once through the inner leaf it reaches the plaster which is highly absorbent. The moisture will then rise up the plaster, often up to 1 metre in height hence the term rising damp. So whilst there can be a capillary action up through bricks below ground level they would still need to breach the cavity onto the inner leaf, hence most rising damp is caused by penetrating damp.

The other issue can come from solid floors, where the DPM has broken down or not been installed correctly. The same principle applies though


I have followed the links and the published date is 1997 & 2007 for various articles. The first recorded report that rising damp was a myth was published in 2008 (I had to google it). Since then the theory has been gaining momentum. I understand the science for why it doesn't exist, but not for how it occurs. This doesn't necessarily mean that I am right, just that I am inclined to believe that it is not as common as originally thought.

See above, trust me it exists. It's not a particularly common problem today in so far as it is usually caused by a breach of damp course (either externally or internally in the cavity) rather than a faulty damp course. Back in the 1980's when I worked as a Building Surveyor for a local Council we had around 4000 homes, or which less than 5% had true damp problems. Most of these were in houses built back in the 1930's and were sorted hence why few suffer now.

Your comments on the volume of moisture expelled at night is really insightful. We are now looking for a second dehumidifier for our bedroom. We have one downstairs, as we have a marine tank and this is taking 5 litres of water out of the air a day. With this amount of moisture inside buildings surely this is a major contributor to damp in houses?

Now you are confusing condensation issues with damp, which are two completely different issues. Yes moisture expelled by us, along with cooking and bathing is a major cause of black mould, streaming windows etc. but it is preventable without any technical intervention. Whilst a dehumidifier is probably a good idea if someone is asthmatic for example, using the measures I mentioned previously should be more than adequate for most households.
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Re: Things you've always wanted to know......

Post by southbrishammer »

Things I want to know: How did the Things I want to know thread turn into the dampcourse thread? I much preferred it when people just talked b*llocks.
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Re: Things you've always wanted to know......

Post by -DL- »

Do you have to clean and hoover your car when your handing it in as PX against another one?

Picking a new one up Thursday, and mine's in good need of both, but don't really want to waste a tenner in getting it done if it doesn't really matter...
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Re: Things you've always wanted to know......

Post by 1875Hammer »

-DL- wrote:Do you have to clean and hoover your car when your handing it in as PX against another one?

Picking a new one up Thursday, and mine's in good need of both, but don't really want to waste a tenner in getting it done if it doesn't really matter...
I wouldn't bother if you've already agreed a price and haven't had a fire in the back seat. They're going to do a better job than you if they are reselling it.
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Re: Things you've always wanted to know......

Post by -DL- »

1875Hammer wrote: They're going to do a better job than you if they are reselling it.
I've never had a dealer do a better job at detailing than me yet 8-)

(I wasn't going to do it - I was going to pop it down the road)
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