Mystical damp hearth

[thehedgehog]

Hello!
We have high (average 70-80%) humidity in our living room..we have two fireplaces, one has been closed off and one is open.
Upon moving in in June we've removed bricks until we reached the hearth.

In the summer we could notice that the original suspended floorboards that touched the cement base got wet when it rained. We since then removed a gutter running into a faulty drain and we noticed less wet floorboards. But it's still noticeable.

Could this be perhaps that the foundation is overall too wet and eventually the concrete block soaks up moisture? That's my best bet but I would love to hear your thoughts on this.

Ps. The chimney has been repointed and capped.
See photo of the hearth, with visible damp patches and wet adjacent flooring

 

[Kearn]

Chimney stacks are notorious hotspots for moisture being pulled up from the ground. We get visible damp marks a foot or so up the stone jambs of our fireplaces when the ground gets really wet - we have bedrock limestone only 300mm beneath us, which doesn’t percolate rainfall away quickly.

 

[a twig]

Nail on the head there Kearn, and a large part of the reason why slate was historically such a popular choice for hearths

 

[thehedgehog]

Thanks for that. So it sounds like this might be a sign that there is not sufficient drainage? We're debating if we should replace our ancient soakaway in the front of the property.
Or, would you "damp proof" it with a membrane to stop the moisture travelling to the flooring?

Chimney stacks are notorious hotspots for moisture being pulled up from the ground. We get visible damp marks a foot or so up the stone jambs of our fireplaces when the ground gets really wet - we have bedrock limestone only 300mm beneath us, which doesn’t percolate rainfall away quickly.

 

[noj]

It may just be that more drying time is needed. You've said the floorboards are less wet now and I'm assuming it's only been a couple of months (of not great weather) since the last of your drainage work.
It can easily take at least six months for saturated masonry to dry...

 

[a twig]

Definitely worth investigating the soakaway more generally though, typically lucky to get more than 15-20 years out of one before it gets clogged.

 

[Cubist]

That hearth will be standing directly on the soil below the house. Given that this property has been afflicted with a number of poor drainage issues externally, particularly at the rear and associated with poorly sited waste pipes, together with the fact that it stands on an old flood plain, may have a significant bearing on this problem. Some, possibly all, of the damp seen in the hearth and leaching into the floorboards may be due to rising damp rather than from the chimney.

You might be wise, when time and opportunity permits, to check the void beneath that floor to check the condition of the soil below and the woodwork comprising the wooden floor itself for signs of damp penetration, fungal infection and rot.

 

[Kearn]

I assume you may be removing the laminate over the boards? That will help with slowing the moisture to escape into the room.

As Cubist says, If you lift a board near the hearth, you may find there’s inadequate space below. Next to our stack, under a later suspended floor, the mice shifted earth from under the slabs in the adjacent room, and piled it up so it was in contact with the underside of the floorboards. Rotted right through. I filled up about 7 or 8 rubbish sacks. A year later, same again!

 

[thehedgehog]

That hearth will be standing directly on the soil below the house. Given that this property has been afflicted with a number of poor drainage issues externally, particularly at the rear and associated with poorly sited waste pipes, together with the fact that it stands on an old flood plain, may have a significant bearing on this problem. Some, possibly all, of the damp seen in the hearth and leaching into the floorboards may be due to rising damp rather than from the chimney.

You might be wise, when time and opportunity permits, to check the void beneath that floor to check the condition of the soil below and the woodwork comprising the wooden floor itself for signs of damp penetration, fungal infection and rot.

Thanks Cubist for your input. This fireplace is not very close to the rear, so I thought perhaps they are two separate issues, see floorplan. I've had the soakaway surveyed by CCTV and it's not blocked so I am a bit on the fence if a new one is needed. But perhaps it is if the hearth is getting this wet.

Will be investigating the status of the subfloor after Christmas, bracing ourselves ahead of that!

 

[thehedgehog]

I assume you may be removing the laminate over the boards? That will help with slowing the moisture to escape into the room.

As Cubist says, If you lift a board near the hearth, you may find there’s inadequate space below. Next to our stack, under a later suspended floor, the mice shifted earth from under the slabs in the adjacent room, and piled it up so it was in contact with the underside of the floorboards. Rotted right through. I filled up about 7 or 8 rubbish sacks. A year later, same again!

Pesky mice! Hopefully we don't have any of that but we lifted one floorboard and it was damp underneath.
Will remove the laminate flooring, but we have a inquisitive toddler so we need to make sure we have a proper exit plan if we start. The whole living room smells musky so can't wait to get started.

 

[Kearn]

Pesky mice! Hopefully we don't have any of that but we lifted one floorboard and it was damp underneath.
Will remove the laminate flooring, but we have an inquisitive toddler so we need to make sure we have a proper exit plan if we start. The whole living room smells musky so can't wait to get started.

I was amazed at how much soil they’d shifted since I last cleaned it out! More worryingly that there is a maze of runs under our original limestone slabs, making them almost suspended in areas! Suffice to say, the crappy rotten boards will be replaced with a solid floor. Ours was conveniently dug down to bedrock for good measure, so any rain and it’s puddling slightly under the boards! Also means our stone plinth wall no longer has any footings….!

 

[Jonty1234]

Hi hedgehog, it might not be identical but i think i'm having similar issues to you and have had a bit of input in the below post.

Damp Hearth and Wall

Hi All, I have an issue of dampness around a fireplace hearth that I’m currently trying to resolve with help from here and other similar forums. I have taken various bits of info/advice from here before and I’m back now to post for the first time so any help would be much appreciated. To...

www.periodproperty.co.uk

In short, water rises up from the ground like you say, through the infill that is possibly under the concrete slab, and makes the joists supporting the floorboards wet. The end result is damp floorboard edges where they touch the joists below.

The edges of our floorboards tended to dry out when there wasn't any rain but would show signs of dampness the day after any rain. Upon removing the concrete slab it was quite obvious that the joists were getting wet in places but have remained generally dry since we have been able to temporarily add in a DPM. I would guess its a pretty common problem in most houses but it isnt until you get back to bare floorboards (which most people probably don't do) that you notice it.

 

[Cubist]

You have to keep in mind too that we have all continued to see heavy and consistent rain across the country. All of that water must ultimately find its way back to sea level or become trapped in underground aquifers or evaporate back into the atmosphere. Here, the water from the last rain storm a few nights back can still be heard running through the ditches in torrents. The land beneath all our homes and gardens is undoubtedly still be sodden and it may take days or even weeks for that water to dissipate through both natural and manmade systems. The evidence of this is all too apparent, albeit that there may be significant variations depending on local altitude and topography. Properties standing on old flood plains will be much more likely than others to see direct evidence of damp rising from that sodden soil layer and it is also likely to persist longer as water continues to drain from higher ground.

There is only one conclusion to be drawn from this - Cnut failed dismally and so will we where rising damp is concerned as there are absolute limits to what we might be able to do to prevent the root cause. All you or I can ever do is to seek to manage and control the effects by diverting as much water as we can away from our homes and limit its ability to climb up through our homes walls and floors - theres an unmentioned reason why the large concrete slabs on which most houses have been built since the 60s are called 'rafts'.

A side bar to this discussion; have you ever noticed that the smell of damp in your home is sometimes stronger in the mornings? If so, you too may have been guilty of looking down at your floors and walls for the cause when you should have looked up at the night sky to find the real culprit.

 

[Cubist]

the mice shifted earth from under the slabs in the adjacent room,

Kearns tale of mining mice reminded me;

One of the smallest rooms on the 1st Floor here has a part of the stone chimney breast forming one of its walls. Whilst standing in there minding my own business one day my eye was drawn to movement caught in the corner of my eye. Being a trifle occupied at the time I controlled my startle while I watched a shrew race across the ledges of several stones before finding a handy escape route. Its not just mice that will mine their way indoors - and some seem able to tunnel their way through mortar too.

 

[Kearn]

Kearns tale of mining mice reminded me;

One of the smallest rooms on the 1st Floor here has a part of the stone chimney breast forming one of its walls. Whilst standing in there minding my own business one day my eye was drawn to movement caught in the corner of my eye. Being a trifle occupied at the time I controlled my startle while I watched a shrew race across the ledges of several stones before finding a handy escape route. It’s not just mice that will mine their way indoors - and some seem able to tunnel their way through mortar too.

Before we started our major conservation project, squirrels had taken up accommodation in our attics… they like to gnaw like rats!

 

[Stevers]

Given that cute little beady eyed field mice sound like rats, squirrels must sound like beavers!

 

[thehedgehog]

Hi hedgehog, it might not be identical but i think i'm having similar issues to you and have had a bit of input in the below post.

Damp Hearth and Wall

Hi All, I have an issue of dampness around a fireplace hearth that I’m currently trying to resolve with help from here and other similar forums. I have taken various bits of info/advice from here before and I’m back now to post for the first time so any help would be much appreciated. To...

www.periodproperty.co.uk

In short, water rises up from the ground like you say, through the infill that is possibly under the concrete slab, and makes the joists supporting the floorboards wet. The end result is damp floorboard edges where they touch the joists below.

The edges of our floorboards tended to dry out when there wasn't any rain but would show signs of dampness the day after any rain. Upon removing the concrete slab it was quite obvious that the joists were getting wet in places but have remained generally dry since we have been able to temporarily add in a DPM. I would guess its a pretty common problem in most houses but it isnt until you get back to bare floorboards (which most people probably don't do) that you notice it.

That pattern sounds much like the one in ours - signs of water the day after a heavy shower.
Besides putting in a DPC, what is your plan for sorting the issue out if I may ask?

 

[thehedgehog]

Kearns tale of mining mice reminded me;

One of the smallest rooms on the 1st Floor here has a part of the stone chimney breast forming one of its walls. Whilst standing in there minding my own business one day my eye was drawn to movement caught in the corner of my eye. Being a trifle occupied at the time I controlled my startle while I watched a shrew race across the ledges of several stones before finding a handy escape route. Its not just mice that will mine their way indoors - and some seem able to tunnel their way through mortar too.

That is definitely an unusual pet!

 

[Cubist]

That is definitely an unusual pet!

Twit and his brother Twoo being of nocturnal habit aren't much use in daylight so on occasion I am to be found ensconced in our back garden watching for the herd of small elephants - aka squirrels - that frequently romp across the ridge of the thatch. My equivalent of a Fairground Shooting Gallery!

 

[LadyArowana]

Twit and his brother Twoo being of nocturnal habit aren't much use in daylight so on occasion I am to be found ensconced in our back garden watching for the herd of small elephants - aka squirrels - that frequently romp across the ridge of the thatch. My equivalent of a Fairground Shooting Gallery!

Did soeone say elephants? We have so many of them here, but they have behaved themselves so far. Have only found two mice. One mummified in a pile of curtains which our delghtful tenants had taken down and left in a heap next to a basement wall, and one sad little soul recently demised in our under pavement vault. Both given decent burials in the garden.