Removing possible bitumen paint on exterior wall

[bp]

Hi,

I have been having a few problems with damp in my house. I have posted before about this but have come up with some more info (different) so I thought I'd post new. I have read some other posting on this but could not find an answer

I Live in an end of terrace which I bought only a while ago. There is an alleyway one side of my house - hence end terrace. When I had the house surveyed, I was told there was damp on the end terrace wall (the one on the side of the alleyway). I was told this was due to the floor level of the alley way bridging the dpc. Solution from him was to lower the floor level of the alleyway to 2 brick lines below the dpc. I originally posted about this is and the generally opinon was that the floor level was too high and I needed to lower it.

Another solution offered was to use a disc cutter and cut out a channel

6 inches away from the wall, along the full length of the wall and dig down to the correct level. Create soak away and filling the channel with gravel.

I have spoke to a few builders about this and from them I have discovered sometihng else.

The whole wall externally is painted black (all the way to the chimney stack). I originally thought this was just exterior paint (weatherproofing), however one builder told me that it looks like bitumen paint. He says it may have been put there to prevent damp getting in, but in reality perhaps it should not be there as by default it also prevents the wall from breathing and could be the cause of damp problems internally. So here are my questions:

How can I tell its bitumen paint

Is he right in saying that it may be causing problems. Could it be causing the damp I am getting on the ground floor (ie on the internal walls I see bubbling of the plaster, loose bits flaking off and small bits of black mould in the corners. I also have some mould appearing in one of the bedrooms upstairs on the inside of the same wall)

Shoud I remove it, and if so how?

Once removed do I need to do anything to the newly exposed wall (pointing, coating with something else etc)

I will not be doing the work my self, but want to get an idea of what could be the cause of my damp problems before I get anyone to start any work

Many thanks

Bhupesh

[Stuart Noble]

Wipe it with kitchen roll soaked in white spirit. Bitumen is brown in solution although it looks black in a solid form. I can't imagine anyone would choose black to paint a wall. Whatever it is, it sounds like it should come off and the procedure would be the same. If it's on the bricks, paint stripper (probably 25 litres plus). If the wall is rendered, might be easier to chop the render off. I don't envy you. It's going to be an expensive job and I think I might look for obvious places where the coating has failed before committing myself to drastic measures. You might be able to patch those areas with something similar. There are 2 basic approaches to this. One that the coating is impermeable enough to prevent moist air getting out. The other (and much more likely IME) that it's leaking and allowing water in. Observation in different weather conditions might give you a clue.

[Peter Parry]

Has the house been fitted with new windows (double glazing)?

[bp]

HI,

Thanks for the replies.

Yes there is double glazing. I did think that there was a ventilation problem. The previous owner has fittied a vent (air brick) at the front room. It is high up - near the celing.

Also I checked the air bricks. Most were blocked. I have cleared them. There are 2 along the black wall (i.e. along the alleyway). However since the floor level is higher then the air bricks, someone has created an opening to allow the air to flow. There was alot of dirt etc in there which was blocking them. I have opened them now, bt I guess I will have t wait and see if things get any worse. If not I guess blocked vents were to blame.

About the removal of the paint, could I sandblast it off? Or is paint stripper the best option.

Thanks

Peter Parry wrote:

[Stuart Noble]

I doubt if you could blast bitumen. Too rubbery. I wouldn't pin all your hopes on the ventilation issues

[Peter Parry]

The pattern you are describing of mould on corners and upstairs is very suggestive of condensation. I'd be inclined to concentrate on proper heating, ventilation and possibly insulation of walls where they are enclosed (within built in wardrobes etc) before trying to remove the paint on the outside.

Also before going foe expensive solutions look at the simple standard things of clearing all rubbish and plants away from the outside wall and creating a gravel French Ditch around the sides.

If it gets to that look at employing a commercial sandblasting company - with domestic equipment it will take you ages and is unlikely to work well. I'd try the simpler bits for a year first.