Condensation behind kitchen unit.

[amfisted]

This morning I happened to pull the washing machine away from its housing under a worktop and against the kitchen wall, for no other reason than that I regularly do that sort of thing in order to check for problems. I found that the floor, which is plastic tiles on concrete, was pretty wet, but I wasn't particularly concerned because the copper pipework for the washing machine was festooned with tiny droplets of water, indicating nothing worse than condensation. I say nothing worse...but...

...whilst I had the machine out I noticed that underneath the adjacent sink unit the wall was black with mould and there were droplets of water adhering to the underside of the baseboard of the cabinet. I squirted as much mould killer as I could into the space, but clearly there's an issue there that goes way beyond cleaning. The previous owner has presumably diagnosed the problem as rising damp because there are injection holes along the wall outside the problem area, but I'm pretty sure its condensation.

I cleaned the mould at the back of the same cupboard about two months ago, but when I removed the contents today to check the backboard I found that the mould is back with a vengeance.

The property was built circa 1973 and has concrete floors throughout.

As to solutions, well--apart from cleaning, I'm a bit stumped. Would installing an airbrick in the problem area, underneath the unit, be likely to help? The kitchen has a decent extractor system but clearly it cannot address the problem of damp caused by condensation behind fixed units.

Any suggestions as to an approach to this problem welcome.

Edit: the seal between worktop and wall appears to be sound and I can't find any evidence of leaks in the kitchen waste pipes. Nor are there any pipes in the problem area behind the unit.

 

[Mikefromlondon]

This will now tempt me to look into behind my own kitchen units, about 3 or 4 years ago, I fitted new kitchen units and one small high level window was in the way of one high level kitchen unit, so I covered this window, which is double glazed, with a white face hardboard, so from the outside you would see a white screen, and then o bolted my units covering this window entirely, I did not seal any gaps between the high level units and the wall, but now i can see that white hardboard has acquired black mold and the window has fair amount of condensation, I have an extractor fan as well and often people using the kitchen don't turn it on, but I will be surprised if the bottom units have a similar problem on mine.

You could try a small fan left running behind 24/7, though my kitchen wall at this property is cavity wall, yours build recently should also be a cavity wall, but who knows there may be a slow leak from somewhere? you will probably have to dry everything and see where this moisture is building up from.

For the time being can you not open your window and extractor fan and the door whilst cooking to rule out any problem associated with cooking fumes and moisture, this way you would be able to get closer to if there are any leaky pipes causing your problem.

 

[amfisted]

Hi Mike

Yes, for the forseeable future and until the weather warms up I intend to put the kitchen window on the vent setting, and ask my wife to use the extractor at all times when she's cooking. I've taken the kickboard off the unit concerned and sprayed a solution of bleach against the external wall in an attempt to kill any mould.

One other possible cause occured to me. We had a multi fuel stove installed about 3 months back, with the intention of heating all the downstairs rooms as well as the lounge. Unfortunately I found that in the unheated third bedroom (this is a bungalow) the warm air from the stove hitting the cold walls created massive condensation, so for now I've had to keep that door shut unless the room is heated by another means beforehand. Perhaps the problem in the kitchen is down to warm air from the stove entering the cold spot under the unit, condensing on the wall and the underside of the baseboard.

If the mould and moisture persists in the better weather when the stove is no longer in use and the windows are regularly opened, then clearly it warrants further investigation. In the meantime I might try putting insulation under the unit to fill the cold space and see whether that cures it.

 

[Mikefromlondon]

whenever one puts something on boil, like boiling potatoes, eggs, other food, the steam from such cooking escapes the drawing stream of the extractor fan and lands on cold window panes, and they all steam up, despite being double glazed, yet the walls remain dry, so the moist air will only ever settle on cold surfaces, some of my upper kitchen cabinets have glass doors and yet they remain dry, no condensation, if we leave the windows slightly open, condensation goes away as the moist air escapes.

I am not sure if you stuffing insulation under the units to block the gap will help, only perhaps an air tight seal is what may and that would be hard to get it right.
even a small gap can draw in moisture. The gaps on my kitchen units hanging in front of this part blocked window is tiny, probably just a milimeter or two at the most and the bottom part has tiles but I did not seal the top of the tiles to the underside of the top mounted units (wall units) I will be taking the top units down to clean up the window and remove the white lined hardboard screen and use a white plastic screen from a sheet i have bought, this won't encourage mold growth and rehang wall units and seal all around from sides and top and bottom. i didn't want this side window blocked permanently.

 

[vinn]

OP,
You dont know what the cause is. Injection holes imply previous damp problems.
Has retro CWI been injected since new build?
Has cavity debris bridging been mentioned by anyone?
What did your buyer's survey say about this matter?
Why not post pics of the inside wall - & the exterior area with the injection holes.

 

[JohnD]

Quite apart from steam arising from cooking, kitchens are particularly prone to damp problems because they contain waterpipes and drains; some of them under the floor, which may well leak with age, especially if buried in concrete. This would usually show itself near the floor, but would increase humidity so causing condensation in other areas.

Do you have a water meter?

 

[amfisted]

OP,
You dont know what the cause is. Injection holes imply previous damp problems.
Has retro CWI been injected since new build?
Has cavity debris bridging been mentioned by anyone?
What did your buyer's survey say about this matter?
Why not post pics of the inside wall - & the exterior area with the injection holes.

True, I don't know what the cause is; hence my posting on here. However, I'm grateful for all advice.

Injection holes could also be an indicator of misdiagnosed damp problems: in this case, perhaps condensation mistaken for rising damp. I think we all remember that a couple of decades ago it was routine for surveyors to find high damp readings and recommend appropriate work. However, in this case rising damp could be an issue, I agree, so if I find myself having eliminated all other possible causes and that's the only one left, I intend to call in a builder and get it sorted properly.

The injection holes are evident exclusively on the rear elevation, including the majority of the exterior kitchen wall. So I would imagine that yes, this injection is retro.

No mention of cavity debris, no. Not sure how I'd investigate that without ripping the units out.

Our housebuyers' survey only pointed out the existence of the injection holes; there was no recommendation of any investigations.

I will post pics but I'm not sure how helpful they'll be. Interior pics will show the underside of the unit and the mould stains on the wall. Exterior pics similarly would only show the injection holes.

Thanks again.

 

[JohnD]

If you have a water meter, it can confirm the presence or absence of a leak.

How old is the house?

 

[amfisted]

Quite apart from steam arising from cooking, kitchens are particularly prone to damp problems because they contain waterpipes and drains; some of them under the floor, which may well leak with age, especially if buried in concrete. This would usually show itself near the floor, but would increase humidity so causing condensation in other areas.

Do you have a water meter?

We do have a meter, yes.

Both hot and cold water pipes are buried in the kitchen floor on their way to the bathroom, so that is something I'd considered as a source of the problem.

I've checked the meter recently and there was no indication of excessive consumption, but I'll check it again tonight in case something has gone awry over the last few days.

I know the drains are OK because I excavated a short section outside the kitchen last year when fitting a new gully, and since then I regularly check the inspection chamber to make sure the waste runs freely.

Edit: the bungalow was built in 1973.

 

[JohnD]

shine a torch on the glass window of the meter. You will see a bubble. Does it stop turning, when all the taps in the house are off? This detects a smaller leak than looking at the meter reading.

 

[amfisted]

I've checked the water meter and the reading is consistent with previous consumption. We have what to the naked eye appears to be a black and white sectored "wheel" thingy in the middle of our meter, and I know from previous observations that it spins like Hell when a tap is running. It wasn't moving when I checked just now with all taps off.

Presumably this limits the diagnosis to rising damp or condensation?

 

[amfisted]

Incidentally, I read somewhere when Googling for other examples of this problem that someone had tackled it by removing the back board from the unit, thus exposing the inside of the exterior wall. They had cleaned the mould from the wall and the problem hadn't returned, presumably due to improved airflow.

Going back to something I mentioned earlier, unless it is rising damp would it serve any useful purpose to install an airbrick in the wall under the unit?

 

[JohnD]

if the bubble in the meter isn't moving, you probably haven't got a leaking supply pipe. Can you see the bubble?

Have a good feel and a sniff round all the waste pipes. If they go into a brown earthenware pipe or gully, it may well be cracked. Sink wastes and washing-machine wastes sometimes leak, unseen behind the kitchen cabinets. It will probably happen when you pull the plug out, or during spinning, not all the time.

A 1973 house probably has a DPC and cavity walls, but is there any chance water could be splashing up from leaking gutters, or that paving might slope towards the house or be above the DPC?

 

[amfisted]

if the bubble in the meter isn't moving, you probably haven't got a leaking supply pipe. Can you see the bubble?

Have a good feel and a sniff round all the waste pipes. If they go into a brown earthenware pipe or gully, it may well be cracked. Sink wastes and washing-machine wastes sometimes leak, unseen behind the kitchen cabinets. It will probably happen when you pull the plug out, or during spinning, not all the time.

A 1973 house probably has a DPC and cavity walls, but is there any chance water could be splashing up from leaking gutters, or that paving might slope towards the house or be above the DPC?

The garden tap is immediately above the affected area, and when its turned on water does sometimes splash up onto the outside of that wall. However, its rarely used during the winter.

All the kitchen waste pipes appear to be dry, and as above I know the drains are in good condition. The paving outside slopes away from the house and is below the level of the DPC, and there are no obviously leaking gutters or downpipes in the vicinity.

TBH I think my best bet is to wait for the warmer weather, then if the problem persists I'll know it definitely isn't condensation.

Thanks again for your help. ;0)

 

[John D v2.0]

Tbh my money is on condensation, there's a good thermal bridge at the bottom of those walls and there's little air circulation so it's probably cold there, and in kitchens the humidity is often very high.
If so, The solutions would be to reduce the humidity (better extraction during cooking) improve the insulation of that wall-floor junction (tricky) or ventilate/heat that area better.
Apart from Mike's fan idea, you could run a hot pipe along there from the heating. Doesn't have to go anywhere, can just be a 10mm bypass on low and clipped to the wall, run in plastic pipe for ease.
Then any time the boiler is running it'll evaporate any moisture off the wall.