black mould and damp on underlay layed on a concrete floor

[Coz]

Anybody shed any light on this problem? We have recently bought a 1960's bungalow. On taking up the bedroom carpet we noticed lots of black marking on it and it is rubber underneath layed onto the concrete floor. It isnt everywhere and the floor itself looks ok, although the rubber underlay felt damp. Could it have been caused by condensation? In other parts of the property we found black mould spots on some of the walls in the backs of cupboards.

 

[Feltwell]

Has the place been closed up or unheated for long?

If it was only built in the 60's then the floor - which I'm assuming is solid - should have a damp proof membrane built into it. My money is on condensation and the whole place needing a good airing, especially if it's not been lived in for any period of time.

 

[stuart45]

Mould is often a sign of condensation. DPM's became a reg with the introduction of the 1965 Building Regulations.

 

[Flyfisher]

I'm sure I've read somewhere (here?) that black mould indicates condensation because it needs fresh water to grow, whereas damp, i.e. water percolating through bricks and mortars, picks up salts and will not support black mould growth.

Confirmation or correction would be welcomed though.

 

[Coz]

Thanks for that. I am of the opinion it is condensation. The place has been lived in all the time - and we have been there every day since we got the keys but I get the feeling they didnt have the heating on very much and not much ventilation cos of the upvc windows. I think our plan of action is to get some of both into all the rooms and hope it will clear up. Because the underlay was damp underneath and couldnt escape cos it was rubber i think it will do the floors good to get some air to them - Keep everything crossed.

 

[Feltwell]

How much ventilation have you got?

Building regs now demand there is a certain amount of background ventilation, as tightly sealed UPVC windows being fitted to houses with no open flues and no wall ventilation caused problems with mould. When your new place was built with single glazed wooden windows with no seals round the openers this wouldn't have been a problem.

Generally it seems this ventilation is achieved through either trickle vents on the windows or vents through the walls. It maybe that you need to put some vents in.

Quite what the "Passivhaus" people do I don't know - their houses are designed to be extremely well sealed, so I guess they must use a dehumdifier system of some kind.

 

[MatthewC]

Quite what the "Passivhaus" people do I don't know - their houses are designed to be extremely well sealed, so I guess they must use a dehumdifier system of some kind.

The Passivhaus structure behind my house has an air recirculation system which filters, cleans and de-humidifies. What it doesn't do, of course, is to actually cool the air. This was all made very clear at their licensing hearing (when one of the councillors was a heating engineer!), and the approval requires them to keep the windows closed at all times when there is any amplification of sound. I expect that a wedding reception at the height of summer is going to get pretty hot in there!

 

[Feltwell]

Generally when you see these Passivhaus structures on Grand Designs or similar they tend to be very open plan & airy houses - they are so well insulated that I guess they don't get that hot inside in summer, and there's never going to be that many people inside at any one point.

But for a commercial-type building like you've got behind you Matthew I can easily see your point - 50 plus wedding guests on a hot night, they are going to cook in there! I suppose the question for you is what can you do when the inevitable happens and the windows and fire escapes are opened? I would imagine beyond complaining to the management/committee, keeping a log & raising an objection when their licence comes up for renewal, not a great deal. Not a good situation.

 

[AMc]

All I read about Passivhaus suggested that the structure is tightly sealed and all ventilation is forced through a mechnical heat recovery system that warms incoming fresh air with the heat from stale expelled air.
A case study on a German primary school showed it was unheated during the week as the building temp only dropped 0.5C overnight and occupancy heat was used most of the time. There was supplemental heating for the first lesson on Monday.
If the thermal mass of the building is done properly then the building shouldn't over heat with the excess occupant heat, the system should bypass the heat exchangers if the ambient temp inside is at or above its set point.

Of course that's the theory and the Germans have been building Passivhaus for almost 20 years....

 

[Moo]

50 plus wedding guests on a hot night, they are going to cook in there! I suppose the question for you is what can you do when the inevitable happens and the windows and fire escapes are opened?

Even with top-quality double glazing some of these sound systems get wound up so high that you would not only be able to hear the noise - you'd actually feel it.
One possible solution would be to instal a sound sensor that cut off the power supply to the source of the "music" should it exceed a specified limit. And as back-up the doors and windows could be fitted with switches that cut the sound should they be opened: Elf'nSafety would approve, because it would be difficult to organise a rapid evacuation if the customers couldn't hear instructions over the thudding of the "music".
I'm sure that in the interests of good neighbourliness and public safety the custodians of the hall would welcome these friendly suggestions.

 

[Gareth Hughes]

50 plus wedding guests on a hot night, they are going to cook in there! I suppose the question for you is what can you do when the inevitable happens and the windows and fire escapes are opened?

Even with top-quality double glazing some of these sound systems get wound up so high that you would not only be able to hear the noise - you'd actually feel it.
One possible solution would be to instal a sound sensor that cut off the power supply to the source of the "music" should it exceed a specified limit. And as back-up the doors and windows could be fitted with switches that cut the sound should they be opened: Elf'nSafety would approve, because it would be difficult to organise a rapid evacuation if the customers couldn't hear instructions over the thudding of the "music".
I'm sure that in the interests of good neighbourliness and public safety the custodians of the hall would welcome these friendly suggestions.

Not amplified music, I know, but that does sound horribly like the solution that was imposed on St Andrew's Hall by that unspeakable (fortunately now no longer with us) solicitor, which ruins concerts there.

 

[Feltwell]

What "solution" was that Gareth?

 

[Gareth Hughes]

A light comes on and starts flashing, and the orchestra have to play the 1812 Overture quietly after 8pm, or risk the electrical supply to the stage (portable lighting only, I suppose, with an unamplified orchestra) being cut off. The audience are only able to applaud quietly too. It is an absurd situation for the building that is the nearest equivalent city-centre Norwich has to a concert hall, imposed on the demands and threats of a solicitor who lived round the corner and who also made it impossible for cafes in the area to have pavement tables. He's dead, but his legacy lives on.

 

[Feltwell]

No chance of getting that condition removed now the main protagonist is pushing up daisies? Or ignoring it and seeing if any complaints or enforcement action results?