Painting a rendered wall

[frogger]

I am looking at painting a rendered wall of a garden bed. The wall is around 1 meter tall and is double brick. As the garden bed contains a good amount of soil for the plants there can be some moisture in the ground. At times the rendered wall which has been drying now for a few weeks does look blotchy at times (especially after rain).

My question - Is there something that I should put on the wall to prevent the paint from bubbling off etc because of the moisture behind ? I will be using dulux exterior weather shield paints

Thanks
Frogger

[Dirty Doogie]

A layer of thick black polythene plastic will do the job.

[frogger]

So your saying put the plastic on the inside of the wall between the soil and wall itself ? Infortunatly there are already established plants in the way and I will not be able to dig out the inside of the garden bed.

[Dirty Doogie]

Hmm buggar! Is the render on the wall cracking or flaking at the moment?

[Dirty Doogie]

Or is the mortar crumbly ? Moisture will definitely be coming through the brick I suspect. Paint is likely to just bubble.

Apart from a membrane at the back of the wall - the only alternative I can offer is to face the wall with a sheet of 4.5 mm hardiflex that has been sealed on the back with something like Bitkote.

[frogger]

I was afraid you were going to say something like that. Maybe I can try using some Dulux Weathershield X10. If it does bubble I guess the only alternative is to dig out the garden bid close to the wall and put some membrane on it ?

[Dirty Doogie]

Well if the current mortar is in OK condition simply use a limewash or a cement based paint to change color. A layer of acrylic paint will form a little dam on the surface of the wall - with possible rsults of bubbling flaking paint where as limewash or cement paint will let water gas through.

[frogger]

hhhhmmmm. I know what you mean. Its just that I have a joining wall with the colour that I wish to continue along the garden wall beds. Maybe ill try and put one coat on. See how that goes for a few weeks with rain etc and then add future coats. If it does bubble I will need to dig out bed and put a membrane on the inner wall
How long should it take for the paint to bubble off the wall if there is water coming thru ?

[Dirty Doogie]

M aybe a month - probably depends on weather. You might get away with a thin coat but i suspect that you will want a full body color to match your adjioning wall.

I have been told there are some hi tech membrane paints that wont bubble etc - but I havent used any or seen any myself.

[frogger]

ok... Thanks for your help with that. Ill try and do some further research

[Slobba]

you should let the render dry for at least 2-3 months...seal and paint. you wont be able to stop any form of water from the outside of the wall with just paint...its like anything paint it once and you will need to repaint another day...you will need a membrane on the inside of the wall

[frogger]

Thanks Slobba,
I think your rite. A membrane looks like my only option.
Is there a particular membrane / product I should use ?

[micktb]

yep energy star astec paints have a product for waterproofing not shaw if it comes in colours can find out for ya

[frogger]

MickTB,

Thanks for the heads up on these energy star astec paints. They sound like the go for me. Spoke to the rep there and they sound like the type of paint I am after. Can handle the moisture by expanding and the rep seems to think that I will not have a provlem with the dampness.
Thansk again.
Jason