Mould On Wall

[keith lockey]

My friend is having some problems with mould on one gable wall. She has tried anti-mould spray, etc, but it has returned. has anybody got a sure-fire solution. Cheers.

Edited January 3, 2014 by keith lockey

[Symptoms]

Is the mould on the inside or the outside?

[keith lockey]

Is the mould on the inside or the outside?

 

Inside - bedroom wall.

[Symptoms]

The cause is likely to be condensation ... warm, humid air in the house hitting that cold gable wall causing the condensation and the resulting mould.  Stop the condensation and you stop the mould growth.  Ventilation is the key (tough in winter when trying to keep the heat in) - even a tiny opening is good.  Maybe during the day when the house is unoccupied.  Also, reduce the amount of moisture in the air - don't dry clothes over radiators, use extractor fans in the kitchen and bathroom to get the moisture outside, hose the tumble dryer outside (even those that have built-in condensors - get a conversion kit).  Insulate that gable wall with cavity wall insulation (often free via grants via energy supplier)  which is easy to inject from the outside ... assumes the house has cavity walls,  if not, then insulate with foam-backed plasterboard on the inside.  This is a bit more disruptive but within the scope of a reasonably decent DIYer and not too expensive.  The point with insulating that wall is that once done it won't be cold so condensation won't happen and mould won't form.  Obviously, your friend (or you) will need to check there are no other sources making that 'damp', like leaking gutters, downpipes, bridged damp-proof courses, etc.

 

It doesn't matter how much spray your friend puts on the wall the problem won't be fixed without doing the above.  Get your friend to contact their energy supplier to see if they can get freebie insulation - get the whole house done and enjoy how snug the house'll be.

 

Mould is harmful to health (breathing in the spores).

Edited January 3, 2014 by Symptoms

[mickypotts]

If the house is stone or brick check the gutters outside for leaks when it rains, it could also be creeping damp from the ground up on the 1st floor

[keith lockey]

Thanks for your comments and advice it's actually my friend's daughters property which she rents out.  (Not me Symptoms - if it was my house I'd be okay about asking for advice in the open) The mould is occurring in two places; the bedroom wall, and a storage cupboard - both on the gable wall. The downstairs flat is okay. Someone else mentioned a Sky dish - that maybe it wasn't sealed properly and the water is seeping in. Then someone else mention putting PVA paint on it - it acts as a glue barrier. Anyway, keep your advice coming and I'll pass the messages on - I'm going to have a look at it on Monday. Cheers everyone.

[Adam Hogg]

Keith L,

 

Has the Flat got a Pitched or Flat Roof?

If Pitched is it slate tiles?

There maybe damage to the slate/s or one or several maybe missing causing water to come into the building.

If it is a flat roof there maybe damage to the Felt roof or it has reached the end of its life, Also Check Weatherboards to see if they are damaged or rotten if they are replace them as water will be coming in from there.

Also If it is a Sky Dish that was not sealed properly or a low grade Silicon was used remove all of it and redo the job with a good quality Silicon any builders merchants (MKM, Travis Perkins, Jewsons, etc.) will help you get a good quality Silicon.

[Symptoms]

Putting on PVA will not fix the problem; the wall will still be COLD.  A cold wall is the problem, so you have to find out WHY the wall is cold;  moisture is likely to be the cause.  The problem with applying a sealant (PVA, oil-based paint finishes, or similar) can also mean that any moisture in the wall has no chance of evaporating ... this is a natural process that walls should be allowed do.

 

As it isn't the whole gable wall then, as I mentioned earlier, it could be something she is doing on the inside - laundry drying, shower/bath/cooking steam.  Rising damp from the ground cannot get that high so look down from the roof line for possible causes.

[keith lockey]

Thanks Symptoms. I will tell my friend about the PVA problem tonight.

[Orloff]

Keith, Sym is right about insulation and ventilation, but if room is heated more, the wall will be warmer.

[Symptoms]

"... but if room is heated more, the wall will be warmer."

 

Not strictly true Orl ... the warmer the air the more able it is to hold moisture.  So always the first thing to do is to reduce moisture (from whatever source) within the building.  If a wall is damp (say from condensation) then it MUST be colder than the room - it doesn't matter how high the central heating is turned up;  if it's colder than the rest of the room it will attract condensation.  A vicious circle.

[Brett]

As symptoms has said, get to the cause of the issue would be the best bet.

Keep the windows on night lock in unoccupied rooms during the day. Trickle vents on PVC windows should be open as per code with condensing boilers.

The problem is that a lot of PVC windows were installed prior to like for like rules coming in and a lot of houses had non vented windows put in then boilers which require ventilation after.

As for the warm damp air which will be causing the problem. If you can recycle the air in the house with cool dry air it will also be easier to heat.

As for neutralising the mould, rub down the affected areas with a sugar soap but use bleach, normal toilet bleach will suffice. This will stop the mould on the surface and still allow the wall to breath.

[Symptoms]

Bleach has a high pH so isn't effective at killing mould spores ... it tends to only whiten the surface spores so appears to person applying the stuff to be effective;  any mould below the surface in a 'porous' wall coating, like plaster or plasterboard, remains unaffected.  The fumes when applying bleach are hazardous so should be avoided by those with iffy health.

 

A much more effective (and safer) method is to use borax powder, diluted in water, as the removal/killing medium.  Ditto white vinegar/water solution.