sealing render with paint?

[lholman]

All,

I have been speaking to a potential vendor and he is trying to convince me that what seems like penetrative damp through the gable end wall can be combated by simply, and I quote:
"scratching off all loose paint, fill any small cracks and re-decorate the wall with weatherproof exterior masonry paint. This together with similar repainting work to the rear of the house will prevent rainwater ingress problems".

I recently posted this topic: http://periodpropertyshop.co.uk/phpBB2/viewtopic.php?t=6683&start=0&postdays=0&postorder=asc&highlight=gable which explains the situation as I see it.

After further inspection there doesn't seem to be many large cracks, but those that are there will obvioulsy need cutting out and filling properly if they go through to the underlying brick work. I also find the quote of £400 for a gable wall of this size remarkable, that wouldn't even pay for the scaffolding.


thanks,

ll

 

[Nemesis]

Oh yes - until the paint cracks, which it will, when all moisture will seep through and be unable to escape.

 

[Lime]

I think this treatment would last for about six months.

 

[lholman]

Cheers for the quick responses guys.

My plan of action for treating this wall (and the rest of the house), taking my current knowledge into account is as follows:

1) Get current flaked paint removed down to the render, cut out and fill any noticeable cracks in render.
2) Remove render at base of walls up to and above the damp proof course (around the complete property) while installing a bell end at the foot of the render to stop water running down the wall on to the exposed brickwork and above DPC.
3) Repaint all exposed and treated render with a suitable external coating, (this is where I need a bit of advice as what is best?)
4) Re-point all exposed brickwork below render.

Is there anything I'm missing anything out?

ll

 

[Johneds]

What is the render made of? If it is a cement render you will probably not be able to eliminate dampness altogether. Sealing will only make it worse.

 

[lholman]

I believe it is cement render as opposed to original lime. What would you suggest is the best cause of action then?

 

[Johneds]

Ideally I would remove the cement render and replace with a lime based render. But I realise that might be a job too far.

Next best is to do the repairs but don't seal. If you must paint for aesthetic purposes then use a mineral/silicate based paint.

 

[lholman]

Unfortunately as you said this is a job too far I believe.

What is the logic and science behind not sealing, does it stop water being trapped in the render and workign its way through to the brickwork?
I would like to paint as it's a nice road with all other houses on both sides painted.

 

[biffvernon]

The silicate paints from Beeck are very vapour permeable, allowing the the wall to stay dry. Talk to Mark Womersley at Womersleys the builders' merchant for discerning builders.

 

[lholman]

Many thanks biffvernon I will be sure to speak to them if we go ahead with this purchase. I have started to read the 'technical guide sheets' and it mentions these paints are are for mineral facades, particularly recoatable lime, lime based cement plasters, porous stone etc. I assume they are still more than suitabel for cement render?

ll