Mystifying damp issue

[Lacan07]

The idea of making an opening in the floorboards is new to me and I'm not aware of it ever having being incorporated into a building as built. Won't it give you a cold draught?

I have never noticed any issue. With an open fire you need some ventilation anyway.

Should you be able to organise the underfloor drying out process so it happens completely underfloor then adding insulation shouldn't be any problem. Fibre stuff pinned on with netting better than the solid celotex stuff in case of drying failure.

But if you have essentially earth (possibly with a thin covering of mortar) under the floor, it's is always likely to become damp again; ventilation will help that to be dispersed but I feel that insulation might well hinder that process.

This is my reasoning, preventing the moisture from rising would worry me and I can't help feeling the insulation would eventually get damp too.

 

[MatthewC]

You have two air bricks - this sounds like not enough - in the outside wall. OK, so under the floor in the wall between the rooms there should be holes right through under the floor. Large holes. As if bricks were missing. Then in the outside wall on the other side of the house there should be more air bricks, so the air can flow under the offending room, through the wall, under the next room and out through the other outside wall where of course there should be more air bricks.
Air needs to flow under the floor from the front of the house to the back.
Yes?

Without that situation there is no air flow and damp can build up.

Sometimes the air bricks in front &/or back get blocked. Or another room is built on with a solid floor and no air vents, so the through-flow is destroyed.

My house has just one suspended floor, for the lounge at the front. Before I moved in (the house being empty) an early task was to make sure that the air brick at the front was clear. When the purchase was completed and I started work on the floor, I found that the airbrick had been blocked by a large quantity of cement! :shock:

Having rebuilt the floor myself, we had an open fire installed (because we wanted one); the installers said an air vent for the fire was mandatory and wanted to drill it in the front wall which is 16 inches thick and the building is listed.:evil: :shock: Happily they were easily persuaded to instead fit the vent in the floor beside the fireplace on the side furthest from the front. Thus, having rebuilt an under-floor support wall with gaps as Ivor says, the fire draws beautifully and so I am sure there's good ventilation under the entire floor. It's now over 11 years later and there has never been an issue (such as excessive draught, or damp smell or anything).

 

[88v8]

...fit the vent in the floor beside the fireplace on the side furthest from the front. Thus, having rebuilt an under-floor support wall with gaps as Ivor says, the fire draws beautifully and so I am sure there's good ventilation under the entire floor. It's now over 11 years later and there has never been an issue (such as excessive draught, or damp smell or anything).

I think if the vent(s) is adjacent to the fireplace any draught will just go straight up the chimney and will not be felt in the room and as you say it enhances the underfloor ventilation.

Ivor

 

[monica357]

You can embed pics from an external site such as Photobucket.

There needs to be airflow beneath the floor. Air bricks on one side must be matched by airbricks on the other side. Any walls in between must be honeycomb so as not to impede airflow. Airbricks on one side only are near useless. Piles of debris may be a problem.

Sleeper walls under the floor, the little walls that support the beams that support the joists, those walls should be honeycomb and need to incorporate a damp course.

1910... I would have thought the house would already have a damp course, probably slate?

Your chimney breast... is it shared with the neighbour? Is it used by both of you? If not, are the pots capped to keep rain out, but not sealed so as to impede airflow? Is the flue open at the bottom or has the fireplace been blocked up with no air vent?

Hi Ivor, I can't undestand why I can't attach photos. I used a camera and they are worth seeing.

Anyway-I can't put airbricks on the other side as that's where the fireplace and chimney are on the party wall. The ones I have are on the only external wall in that room. Honey comb means spaced, does it?
Must be shared as neighbour's fireplace is on the other side of mine. I do use mine but not recently with these issues.

So.... if you upload your pics to Photobucket, a paid account in my case, other photosharing sites are available, and then select the pic, click on the Share icon, then Embed, select img, and the size you want, then copy the link and paste it here like this



and you can see the vents I put in either side of the dining room fireplace on our previous house. Avert your eyes from the fitted carpet, 35 years ago I knew no better.....

Anyway, back to your damp. Pardon some random thoughts.

This https://image.slidesharecdn.com/tutorhollowgroundfloorsppt7-170217095142/95/tutor-hollow-ground-floors-2-638.jpg?cb=1487325141 is a honeycomb wall. It does not obstruct airflow. This is how your joists should be supported.

Air bricks are pretty much useless without air flow across the room. As I'm understanding it the house is more than one room thick from front to back and this is like a front or back room, there is another room behind it?
You have two air bricks - this sounds like not enough - in the outside wall. OK, so under the floor in the wall between the rooms there should be holes right through under the floor. Large holes. As if bricks were missing. Then in the outside wall on the other side of the house there should be more air bricks, so the air can flow under the offending room, through the wall, under the next room and out through the other outside wall where of course there should be more air bricks.
Air needs to flow under the floor from the front of the house to the back.
Yes?

Without that situation there is no air flow and damp can build up.

Sometimes the air bricks in front &/or back get blocked. Or another room is built on with a solid floor and no air vents, so the through-flow is destroyed.

How big is the room.... in a room say 12' across I would look for at least 9"x3" air bricks, iron not terracotta. One near each corner and one near the middle. Two sounds not enough. Then on the opposite side of the house, the same.

Stick your head under the floor and look for holes in the dividing wall between front and back. You may have to take up a board or two in the other room as well. This is all a pain, isn't it, but without through flow whatever you do will be treating the symptoms without addressing the cause.

Another thing, on the party wall between you and the neighbour, what's on the neighbour's side? Have you been in for afternoon tea, tea and cake... Might they for instance have taken out the chimney breast, might there be a radiator there that's leaking or some pipes that are leaking? Over the years, stuff happens, and shared walls can become shared problems.

Onwards.

Ivor

You can embed pics from an external site such as Photobucket.

There needs to be airflow beneath the floor. Air bricks on one side must be matched by airbricks on the other side. Any walls in between must be honeycomb so as not to impede airflow. Airbricks on one side only are near useless. Piles of debris may be a problem.

Sleeper walls under the floor, the little walls that support the beams that support the joists, those walls should be honeycomb and need to incorporate a damp course.

1910... I would have thought the house would already have a damp course, probably slate?

Your chimney breast... is it shared with the neighbour? Is it used by both of you? If not, are the pots capped to keep rain out, but not sealed so as to impede airflow? Is the flue open at the bottom or has the fireplace been blocked up with no air vent?

Hi Ivor, I can't undestand why I can't attach photos. I used a camera and they are worth seeing.

Anyway-I can't put airbricks on the other side as that's where the fireplace and chimney are on the party wall. The ones I have are on the only external wall in that room. Honey comb means spaced, does it?
Must be shared as neighbour's fireplace is on the other side of mine. I do use mine but not recently with these issues.

So.... if you upload your pics to Photobucket, a paid account in my case, other photosharing sites are available, and then select the pic, click on the Share icon, then Embed, select img, and the size you want, then copy the link and paste it here like this



and you can see the vents I put in either side of the dining room fireplace on our previous house. Avert your eyes from the fitted carpet, 35 years ago I knew no better.....

Anyway, back to your damp. Pardon some random thoughts.

This https://image.slidesharecdn.com/tutorhollowgroundfloorsppt7-170217095142/95/tutor-hollow-ground-floors-2-638.jpg?cb=1487325141 is a honeycomb wall. It does not obstruct airflow. This is how your joists should be supported.

Air bricks are pretty much useless without air flow across the room. As I'm understanding it the house is more than one room thick from front to back and this is like a front or back room, there is another room behind it?
You have two air bricks - this sounds like not enough - in the outside wall. OK, so under the floor in the wall between the rooms there should be holes right through under the floor. Large holes. As if bricks were missing. Then in the outside wall on the other side of the house there should be more air bricks, so the air can flow under the offending room, through the wall, under the next room and out through the other outside wall where of course there should be more air bricks.
Air needs to flow under the floor from the front of the house to the back.
Yes?

Without that situation there is no air flow and damp can build up.

Sometimes the air bricks in front &/or back get blocked. Or another room is built on with a solid floor and no air vents, so the through-flow is destroyed.

How big is the room.... in a room say 12' across I would look for at least 9"x3" air bricks, iron not terracotta. One near each corner and one near the middle. Two sounds not enough. Then on the opposite side of the house, the same.

Stick your head under the floor and look for holes in the dividing wall between front and back. You may have to take up a board or two in the other room as well. This is all a pain, isn't it, but without through flow whatever you do will be treating the symptoms without addressing the cause.

Another thing, on the party wall between you and the neighbour, what's on the neighbour's side? Have you been in for afternoon tea, tea and cake... Might they for instance have taken out the chimney breast, might there be a radiator there that's leaking or some pipes that are leaking? Over the years, stuff happens, and shared walls can become shared problems.

Onwards.

Ivor

Hi, I have just had a leak expert in, arranged by my insurance-finally they have listened. My neighbours had more leaks from their heating system after having their previous leaking pipe mended.On his side he has two radiators and he hasn't taken out his chimney breast. The leak expert says the water on my sub floor on the party wall side is more than likely due to my neighbour's issues, which they will write in their report. They will also arrange special drying equipment in the next few weeks.They detected no other leaks in my property. I'm starting to wonder if I have wasted thousands getting walls redone! Anyway, I will have to see what this drying process does-I'm not that optimistic, but hey ho! As for tea and cakes-no, no ,no-they are nice enough,but they are just neighbours!!!

 

[Cubist]

.............. My neighbours had more leaks from their heating system after having their previous leaking pipe mended.On his side he has two radiators and he hasn't taken out his chimney breast. The leak expert says the water on my sub floor on the party wall side is more than likely due to my neighbour's issues, which they will write in their report.....

Hi Monica,
Must admit I'm becoming a trifle puzzled by your latest experts conclusion; did he/they examine the next doors property as well as your own?

The reason I ask is that in the event of a leak from their central heating pipes the likelihood is that their property would have experienced considerably more and obvious damage because the water would, at least in the early days of the leaks life, follow the line of least resistance and would become evident in your neighbours plaster and woodwork. Also, as party walls between properties, particularly if they are also load bearing, can be anything up to 30cm thick and may also include a cavity, it would take either a very heavy flow - read torrent - or a steady trickle over many 'years' before the water penetrates to your property.

Personally, I can think of only one scenario in which such a leak could possibly be unseen/overlooked by your neighbours. Its not unknown for idiots to 'bury' copper service pipes in walls leaving just the pipe tails on the surface to make the plumbing connections. When this is done, its good practice to 'wrap' the pipes that will be buried in an insulating tape to shield the bare metal from the corrosive elements found in some mortars and plasters but, through ignorance or negligence, this is sometimes overlooked. In this way, and to my mind just barely feasibly, a leak may arise that could be unnoticed by your neighbour whilst the water penetrates through to your home. As I say though, to my mind thats a hell of stretch.

In your shoes I would be somewhat wary of the advice from your latest expert unless he has directly examined the conditions next door. Not least because your neighbours insurers may contest the finding should there be any claim against them.

Cheers,
Steve

 

[MatthewC]

But if you have essentially earth (possibly with a thin covering of mortar) under the floor, it's is always likely to become damp again; ventilation will help that to be dispersed but I feel that insulation might well hinder that process.

This is my reasoning, preventing the moisture from rising would worry me and I can't help feeling the insulation would eventually get damp too.

Just to clarify, I was not suggesting that one should lay a thin screed of lime mortar; rather, it is what you might find as I think it tended to be done by the Victorians

 

[monica357]

.............. My neighbours had more leaks from their heating system after having their previous leaking pipe mended.On his side he has two radiators and he hasn't taken out his chimney breast. The leak expert says the water on my sub floor on the party wall side is more than likely due to my neighbour's issues, which they will write in their report.....


Hi Monica,
Must admit I'm becoming a trifle puzzled by your latest experts conclusion; did he/they examine the next doors property as well as your own?

The reason I ask is that in the event of a leak from their central heating pipes the likelihood is that their property would have experienced considerably more and obvious damage because the water would, at least in the early days of the leaks life, follow the line of least resistance and would become evident in your neighbours plaster and woodwork. Also, as party walls between properties, particularly if they are also load bearing, can be anything up to 30cm thick and may also include a cavity, it would take either a very heavy flow - read torrent - or a steady trickle over many 'years' before the water penetrates to your property.

Personally, I can think of only one scenario in which such a leak could possibly be unseen/overlooked by your neighbours. Its not unknown for idiots to 'bury' copper service pipes in walls leaving just the pipe tails on the surface to make the plumbing connections. When this is done, its good practice to 'wrap' the pipes that will be buried in an insulating tape to shield the bare metal from the corrosive elements found in some mortars and plasters but, through ignorance or negligence, this is sometimes overlooked. In this way, and to my mind just barely feasibly, a leak may arise that could be unnoticed by your neighbour whilst the water penetrates through to your home. As I say though, to my mind thats a hell of stretch.

In your shoes I would be somewhat wary of the advice from your latest expert unless he has directly examined the conditions next door. Not least because your neighbours insurers may contest the finding should there be any claim against them.

Cheers,
Steve

Hi Steve,
Been a while.
At the moment I have industrial drying equipment drying out the floor beneath the floorboards-since last Tuesday. It is drying-judging by the amount of water I've had to empty from the bucket they left. The first leak from a mains pipe that my neighbours had was about 4 years ago, or so they were told, and this was only detected in around November. Their underfloor was soaking-joists rotten etc. That got sorted. The second leak was a few months back caused by their new radiator pipes being pierced. That is now sorted and I have seen the certificate from the company working for their insurance. But, this means any water penetrating my property would have been longstanding. I have noticed that the bricks on which some joists rest are packed tight with no gaps-someone mentioned this scenario before in the discussion-honeycomb?? I am thinking when all is dried, and I'm guessing drying through the bricks will take time- I will get the joist replaced-it's not rotten- and have the bricks relaid with gaps. Also, I thought I should get the constructional hearth relaid as that seems to rest on a very unstable mess of crumbly brickwork. This would mean getting rid of my stone fire surround, which I hoped not to do, but it's the only way to access all of the constructional hearth. I suppose some kind of damp membrane should be used too. Any ideas who would do this sort of job as not all builders know what they're doing! any comments at all??

 

[Cubist]

Hello again Monica,

Good to hear that you successfully made the transition to the new website - we all owe a debt of thanks to Malcolm for taking it on and keeping us all up and running. One of the big benefits of the new site appears to be that it is easier to upload photographs and, so far, there don't seem to be any silly size limits. If you understand the lingo just drag and drop any photos from your pc desktop directly into a new post to this discussion. For example, this is one of our frequent and uninvited visitors - and yes, thats my back garden.

Any piccies you can supply now of the hearth and the water affected areas would be very useful to those who can provide advice. From what you've said so far though theres nothing that should be beyond any good builder - the hardest part is finding one. Let us know roughly where you are in the UK as theres a reasonable chance someone here may know someone there.

Cheers,
Steve

 

[malcolm]

I've fixed some of the quotes in this thread. My favourite trick is to select the text I want to quote then press the reply button in that post. It's a new feature. I'm glad the source of water has been identified. If the wet joist is not soft it's probably sound and will probably dry out and not need to be replaced. Replacement sounds disruptive.

It's well worth sitting joists onto something waterproof so they don't get wet, but a really bad idea to cover the whole underfloor with waterproofing as that would make the ground wet and water will try to escape up the walls. Better to get the underfloor ventilation right. The joist getting wet in the first place even with water flooding in suggests ventilation is lacking. Crumbly brickwork might well be OK if it was made that way and has worked for hundreds of years. Photos would be really useful and they are possible now. You've got deer Cubist?

 

[Cubist]

You've got deer Cubist?

Coo, this 'highlight-reply' features a goodun. That aside.. being called a dear by someone called Malcolm is a bit unsettling.

 

[Cubist]

You've got deer Cubist?

Apologies, just noticed I'd misread your words Malcolm.

We're on the edge of the Mortimer Forest here so often see fallow deer, including the 'long-haired' variety unique to the area, visiting our gardens and sometimes in significant numbers. They can do a little damage but nothing by comparison to that done by the 'flocks' of marauding sheep that sometimes stray into the formal spaces.

 

[monica357]

Hello again Monica,

Good to hear that you successfully made the transition to the new website - we all owe a debt of thanks to Malcolm for taking it on and keeping us all up and running. One of the big benefits of the new site appears to be that it is easier to upload photographs and, so far, there don't seem to be any silly size limits. If you understand the lingo just drag and drop any photos from your pc desktop directly into a new post to this discussion. For example, this is one of our frequent and uninvited visitors - and yes, thats my back garden.

Any piccies you can supply now of the hearth and the water affected areas would be very useful to those who can provide advice. From what you've said so far though theres nothing that should be beyond any good builder - the hardest part is finding one. Let us know roughly where you are in the UK as theres a reasonable chance someone here may know someone there.

Cheers,
Steve


View attachment 8960

Hi Steve, Been another looong while! Well the industrial drying equipment went a few weeks ago but I don't think it was there long enough. Humidity definitely seems to affect things as I've been monitoring this very carefully with my hydrometer and the changing weathers. I have taken some photos.This shows joist in corner, right side of fireplace. You can see damp patches. These are always the same shape and get darker when humidity is really high. This is further along the same joist.And this one further along same joist. Only this joist is affected this way
This pic shows side of fireplace where this joist is and you can see the crumbly, rubbley constructional hearth below.

Not sure where to go from here. I am thinking to get another company to check properly for leaks and maybe do a bit more drying (the first company was sent by my insurance company). I think I need to have this joist replaced and a few others that look dodgy but not wet. I think I will have to have the fireplace removed to see what's going on in the constructional hearth. Any thoughts. I also thought this pic is interesting. The edges of the boards are damp. These board edges used to be at the edge of the constructional hearth, but I had them cut and turned around. The odd thing is when humidity is higher the exact same part get damp on top wherever I put the board!!!

 

[monica357]

Hi Steve, Been another looong while! Well the industrial drying equipment went a few weeks ago but I don't think it was there long enough. Humidity definitely seems to affect things as I've been monitoring this very carefully with my hydrometer and the changing weathers. I have taken some photos.This shows joist in corner, right side of fireplace. You can see damp patches. These are always the same shape and get darker when humidity is really high. This is further along the same joist.And this one further along same joist. Only this joist is affected this way
This pic shows side of fireplace where this joist is and you can see the crumbly, rubbley constructional hearth below.

Not sure where to go from here. I am thinking to get another company to check properly for leaks and maybe do a bit more drying (the first company was sent by my insurance company). I think I need to have this joist replaced and a few others that look dodgy but not wet. I think I will have to have the fireplace removed to see what's going on in the constructional hearth. Any thoughts. I also thought this pic is interesting. The edges of the boards are damp. These board edges used to be at the edge of the constructional hearth, but I had them cut and turned around. The odd thing is when humidity is higher the exact same part get damp on top wherever I put the board!!!






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[stuart45]

Hygroscopic salts do this to masonry and plaster, which often come from the chimney area. I don't know if they can affect timber in the same way though.

 

[Feltwell]

Hygroscopic salts do this to masonry and plaster, which often come from the chimney area. I don't know if they can affect timber in the same way though.

I don't see why not, it would work in the same way.

 

[Cubist]

Hi Monica,

It"s worth noting that any timbers will absorb moisture much more freely through their end-grain - and will expel moisture via this route just as freely. Its also worth noting that the stains on the surface will never disappear naturally, albeit they may fade and appear to get darker as humidity waxes and wanes. Also, joists mass more than say a floorboard and consequently will take considerably longer to thoroughly dry out. Its hard to tell from your photos but none of the timbers I'm seeing look to be in bad condition.

That hearth and the soil below it may still be very wet from the original leaks and, given its mass, it could take months to thorughly dry. Frankly, unless you can establish that this room is definitely getting wetter then I think further investment in hunts for leaks is likely to be wasted.

Your hygrometer will give you broad indications of the rooms humidity but it is something of a blunt instrument. A better, and much cheaper, tool to keep an eye on how well the timbers are drying out is a Moisture Meter. You can buy one of these for about £20.

Cheers for now,
Steve

 

[monica357]

Hi Monica,

It"s worth noting that any timbers will absorb moisture much more freely through their end-grain - and will expel moisture via this route just as freely. Its also worth noting that the stains on the surface will never disappear naturally, albeit they may fade and appear to get darker as humidity waxes and wanes. Also, joists mass more than say a floorboard and consequently will take considerably longer to thoroughly dry out. Its hard to tell from your photos but none of the timbers I'm seeing look to be in bad condition.

That hearth and the soil below it may still be very wet from the original leaks and, given its mass, it could take months to thorughly dry. Frankly, unless you can establish that this room is definitely getting wetter then I think further investment in hunts for leaks is likely to be wasted.

Your hygrometer will give you broad indications of the rooms humidity but it is something of a blunt instrument. A better, and much cheaper, tool to keep an eye on how well the timbers are drying out is a Moisture Meter. You can buy one of these for about £20.

Cheers for now,
Steve

Thanks Steve. Therefore, it might be best to get rid of my fire surround-what a shame! and so expose the constructional hearth below so I can see how wet it may be if at all. I don't think the room is getting wetter-the only changes occur if humidity rises and those are the ones I've mentioned. I have a moisture meter-what measure should I be aiming for in timber -17? I seem to remember the drying people say this. What sort of builder can restructure the constructional hearth when the time comes-surely it needs to be someone who knows about old properties. And what about damp proofing new joists and the restructured constructional hearth?? I need to be clear about what to ask a builder to do. Thanks for your help so far.

 

[Cubist]

Monica,

If you are convinced the room is not getting wetter there is no good reason to consider removing your fire surround. The hearth will dry out on its own without any interference or intercession from anyone - if it aint broke dont fix it. The humidity changes you are seeing are likely a direct result of heating and ventilation indoors and is precisely the right think and exactly what you need. As far as measures of timber dryness is concerned anything below 20% is good. Based on what I can see there is no need for new joists or re-construction of your hearth and therefore no reason to think about damp proofing these.

Cheers,
Steve

 

[Lacan07]

Your hygrometer will give you broad indications of the rooms humidity but it is something of a blunt instrument. A better, and much cheaper, tool to keep an eye on how well the timbers are drying out is a Moisture Meter. You can buy one of these for about £20.

Cheers for now,
Steve

I thought it was the general consensus that those moisture meters were largely discredited?

A more accurate way of checking for damp told to me on another forum is to drill a hole in the wall and collect the brick or mortar dust - weigh it - and then heat it in the oven on a low temp (120) for say 10 mins - and then weigh it again. Never tried it though.

 

[a twig]

Timber moisture meters are fine for timber, not so much for sticking into plastered walls