Damp house but no sign of damage, just high RH after a lot of rain.

[Greysowhat]

I'm in social housing and the place is fine unless it rains for prolonged periods. When it does the relative humidity (RH) goes up and up. When the weather changes to dry conditions slowly over days the RH comes down again.

The locality has damp ground and I think we are quite close to the water table which rises when it rains. Springs pop up in the local park after an awful lot of rain over days and days! The garden has 2 very wet areas which are close to the 2 worst rooms. I wonder if a spring popped up under the house or maybe it's just sitting in water when the water table rises.

I've been on to the housing people many times about this but unfortunately there are no actual signs of damp in the house such as a smell of damp, mould, crumbling skirting boards or damp patches on the walls. So they say there is no problem. But a couple of weeks ago after a lot of rain the RH was 80%, with temp 18 degrees C.

I ventilate like mad when the house is damp so that would keep mould away.

So can anyone tell me how the place can feel so damp and yet no damp patches or other damage anywhere.

I'm in Northern Ireland. I'll have a proper look tomorrow and get a few pics. But could the DPC be plastered over?? No bricks by the way, it's a kind of pebble dash. Thanks for your help!

But that's exactly what you'd expect to happen because the cold air outside will have a lower total moisture content than the warm air inside. When you open the windows you're letting in colder air which is holding less moisture than the warm air in your house. When you exchange that warm air for cold air the relative humidity in your house will drop.

It might have been rendered over, but this is wrong. Tbe render should stop above the DPC with a drip shape. Render over it bridges the DPC and allows water to travel past it.

Agree
although this is unlikely to be OPs issue because localised damp patches, efflorescence and blown plaster would be evident

Thank you. Well worth investigating.

No, there is none of that which is why the housing people are insisting there isn't a problem. However when we moved in first I noticed that the paint on some of the ceilings had small bubbles, around 5 mm, all over. I sanded it all back and painted again and almost before my eyes bubble appeared. I asked a painter and he said could be because of moisture in the ceiling. Also had trouble painting walls. I used that tough scrubbable paint, matte finish but as it dried it cracked. Asked another painter and he said could be because the walls were damp and the paint dried from the outside in rather than from the wall out which is what is supposed to happen. I painted after a week or so of rain. To get the job done I put on the thinnest coat of paint and used pots of steaming water near the areas where the cracking occurred to stop it happening. It worked!

Are these things any use? Or unreliable? https://www.amazon.co.uk/gp/product/B0DNT39JZ8/ref=ox_sc_act_title_2?smid=A2AVC41AXCKT4J&th=1

The ceiling paint adhesion might have a different cause. If can be dirt or grease that the paint can't stick to, especially in a room where there's been an open fire, a smoker, candles or cooking. I would not have thought the ceiling had distemper on it, at that age.

I'm still wondering about the gutter downpipes, gullies and drains near your patch of wet ground. A 45 year old house is likely to have been built to withstand ordinary conditions, especially if it was originally a council house, which were usually built to good standards, but a broken pipe or drain can deliver a huge amount of water.

Downpipe at the front was checked a year ago and the drain into which it pours was cleared out. The back one seems ok too.

Also the house is on a slope, almost at the top of it. But terrible drainage in the area, all the neighbours complain about moss in the garden. The front here is full of it, the back is not great either.

I just grabbed a quick picture of the wall at the back of the house. The path is dry but there is still a thin wet line running along at the bottom. It's been worse but we haven't has much rain for the last while, Also tide marks from when the damp went higher. I'm not sure if this is normal enough or an indication of rising damp.

This is just around the corner from the first pic, you can see the damp a little better here I think. This is where the kitchen is, one of the worse rooms for high RH

Looking af the wall, I think there is a good chance the DPC is concealed under the lip at the bottom of the pebbledash. This would be correct. The cement plinth on the bottom courses of bricks is undesirable, but probably added to conceal spalling. Do all your neighbours have it?

The bottom of the wall in the first pic shows intense water marks. It is not level, and has either limescale or soap deposits. Stand back and take a wider pic please. I am looking for a kitchen waste pipe from a sink or washing machine, and the reason for the patch seemingly sloping up as it nears the source. It might possibly be due to a dripping gutter.

In your second pic, the plinth is green, indicating persistent damp, probably no sun exposure, and is wetter towards the corner on the left. The path looks surprisingly clean. Has it been pressure washed? If not, the water might be coming out from the floor inside, especially if it is a kitchen. Have you got a water meter, or a young person with sharp hearing? Do you know where your outdoor and indoor stopcock are?

"the house is on a slope, almost at the top of it"

Being at the top of a slope is good, because water will run away from you.

Being at the bottom is bad, because rain will run towards you and may form pools or puddles.

If the RH outdoors is high ventilating won't bring it down inside. You still need to ventilate, but then close your windows and run a dehumidifier. The meaco zambezi is brilliant and can be set to run automatically whenever the RH exceeds a set level. It also has a laundry mode.

"If the RH outdoors is high ventilating won't bring it down inside"

It will in winter, because the house is heated, and the RH will drop.

Those damp meters are fine. I use similar as an architect

What sort of paint are you using
I would suggest a fully breathable paint .
ie water based , nothing containing a glue substance
FB breathable or Earthborn are good

If you check the readings with a damp meter all over the house and it’s high you can prove that to your housing association. Ask them to come round and show them
If the paints bubbling ( or was ) you clearly have an issue with the construction and for now the lack of bubbling may simply be because you’ve been able to hide it. Nothing more.

The dpc should be 150mm ie two brick courses above the external ground level.
Ask your ha if there’s a dpc at the junction of concrete and pebble dash as it looks like it’s been covered over if its there

It's a semi and yes next door is identical. Identical houses across from me are the same except that the plinth is only a couple of inches high. The front of my place is like that too.

Yes you're right, the path next to the green plinth was power washed around 9 months ago.

Not sure about the stopcocks but can find them. Not on a water meter but I have sharp hearing, in one ear anyway!

What issue would cause the bubbling on the ceiling? It was plain ol' matt emulsion. The wall paint cracked. That paint was Johnstones Acrylic Durable Matt. That went on fine after a long dry period. It was after prolonged rain that the cracking happened. Same with the bubbling on the ceilings.

And yes, that damp green plinth is east facing, never gets the sun.

There’s the bad word. Acrylic.
Acrylic doesnt let the building ( walls / ceilings breath

If it started cracking after rain it’s because there is moisture build up and the acrylic is preventing the building from breathing. It will eventually bubble / crack/ effloresce
There will be a problem with the construction behind the area of cracking and at least 1m around it. Guessing your dpm is failing

Again green mould is lack of ventilation
Don't stack stuff up against walls.

You’d be amazed how many people plant right next to their houses and wonder why there’s mould and damp inside

I should have said but it slipped my mind, all the drains were scoped to check for leaks around 9 months ago.

Can a DPM be checked? If so how is it done?

From picture 1, I think water is coming from the gulley on the right, and running down along the wall. Tip a bucket of water next to it and see where it runs.

From picture 2 I think water us coming from that downpipe. Too much stuff in the way, and is to the side of the pic, to see what's going on.

I will guess that your gullies are salt-glazed clay, which is a sort of pottery like an old brown teapot. IME they are always usually cracked or broken.

There might be something else to the far left of the pic but I can't see it.

(Quote above is a mistake)

Gutter downpipes can leak if they are blocked. They are deliberately fitted with unsealed joints so that in the event of a blockage the water escapes from the joint above. You can see it during rain (which is also the best time to look for blocked gutters overspilling)

(I am getting the impression of damp from the water stains and areas of shading on the wall)