Making white (exterior) wall paint stick to mortar rendering
 

Our house is brick built, with mortar rendering over this. The mortar has
been painted with white paint - I can't tell whether it's plain paint or
whether it has sand in it to give it a texture. That was done by the
previous owners before we bought the house two years ago.

Large areas (patches of several square feet) of the paint has suddenly
started flaking off the mortar - it seemed to begin at the same time (late
last year / early this year) in various parts of the wall. The flakes are
several inches square and quite thick as if many coats of paint had been
applied. It is the lower parts of the wall (up to about 6 feet from the
ground) which have flaked, although on the higher parts of the wall, the
paint looks to be cracking and bubbling.

The mortar underneath is sound - that has not started to crack off the
bricks.

What is the best way to repaint it? Is it just a case of using a wire brush
to get off any loose paint, and then painting with Sandtex or some other
outside emulsion paint? Or do I need to first paint the mortar with some
sort of primer and then paint that with the white paint?

Making white (exterior) wall paint stick to mortar rendering
 

On 17/04/2021 14:35, NY wrote:
Our house is brick built, with mortar rendering over this. The mortar
has been painted with white paint - I can't tell whether it's plain
paint or whether it has sand in it to give it a texture. That was done
by the previous owners before we bought the house two years ago.

Large areas (patches of several square feet) of the paint has suddenly
started flaking off the mortar - it seemed to begin at the same time
(late last year / early this year) in various parts of the wall. The
flakes are several inches square and quite thick as if many coats of
paint had been applied. It is the lower parts of the wall (up to about 6
feet from the ground) which have flaked, although on the higher parts of
the wall, the paint looks to be cracking and bubbling.

The mortar underneath is sound - that has not started to crack off the
bricks.

What is the best way to repaint it? Is it just a case of using a wire
brush to get off any loose paint, and then painting with Sandtex or some
other outside emulsion paint? Or do I need to first paint the mortar
with some sort of primer and then paint that with the white paint?
We had the same problem on some roughcast render. Wire brush and/or
pressure washer, followed by fungicide (which is the bit I suspect the
previous owners neglected) before painting.

Making white (exterior) wall paint stick to mortar rendering
 

On 17/04/2021 14:48, wrote:
On 17/04/2021 14:35, NY wrote:
Our house is brick built, with mortar rendering over this. The mortar
has been painted with white paint - I can't tell whether it's plain
paint or whether it has sand in it to give it a texture. That was done
by the previous owners before we bought the house two years ago.

Large areas (patches of several square feet) of the paint has suddenly
started flaking off the mortar - it seemed to begin at the same time
(late last year / early this year) in various parts of the wall. The
flakes are several inches square and quite thick as if many coats of
paint had been applied. It is the lower parts of the wall (up to about
6 feet from the ground) which have flaked, although on the higher
parts of the wall, the paint looks to be cracking and bubbling.

The mortar underneath is sound - that has not started to crack off the
bricks.

What is the best way to repaint it? Is it just a case of using a wire
brush to get off any loose paint, and then painting with Sandtex or
some other outside emulsion paint? Or do I need to first paint the
mortar with some sort of primer and then paint that with the white paint?
We had the same problem on some roughcast render. Wire brush and/or
pressure washer, followed by fungicide (which is the bit I suspect the
previous owners neglected) before painting.
Also, don't use a steel wire brush - bits stick in the render and will rust.

Making white (exterior) wall paint stick to mortar rendering
 

"NY" wrote in message
...
Our house is brick built, with mortar rendering over this. The mortar has
been painted with white paint - I can't tell whether it's plain paint or
whether it has sand in it to give it a texture. That was done by the
previous owners before we bought the house two years ago.

Large areas (patches of several square feet) of the paint has suddenly
started flaking off the mortar - it seemed to begin at the same time (late
last year / early this year) in various parts of the wall. The flakes are
several inches square and quite thick as if many coats of paint had been
applied. It is the lower parts of the wall (up to about 6 feet from the
ground) which have flaked, although on the higher parts of the wall, the
paint looks to be cracking and bubbling.

The mortar underneath is sound - that has not started to crack off the
bricks.

What is the best way to repaint it? Is it just a case of using a wire
brush to get off any loose paint,

Seems unlikely to be viable, why wouldn’t
the paint that hasn’t flaked flake off later ?

and then painting with Sandtex or some other outside emulsion paint? Or do
I need to first paint the mortar with some sort of primer and then paint
that with the white paint?

Lonely Obnoxious Cantankerous Auto-contradicting Senile Ozzie Troll Alert!
 

On Sun, 18 Apr 2021 06:42:48 +1000, cantankerous trolling geezer Rodent
Speed, the auto-contradicting senile sociopath, blabbered, again:

FLUSH the trolling senile asshole's latest troll**** unread

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Making white (exterior) wall paint stick to mortar rendering
 

Are you sure it was not a fly by night coating firm that did it while it was
damp weather and did not use the sealer treatment first. When its done
right this sort of finish last 15 years or more, when its not it cracks and
come off like large lumps of super sized dandruff.
Brian

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"NY" wrote in message
...
Our house is brick built, with mortar rendering over this. The mortar has
been painted with white paint - I can't tell whether it's plain paint or
whether it has sand in it to give it a texture. That was done by the
previous owners before we bought the house two years ago.

Large areas (patches of several square feet) of the paint has suddenly
started flaking off the mortar - it seemed to begin at the same time (late
last year / early this year) in various parts of the wall. The flakes are
several inches square and quite thick as if many coats of paint had been
applied. It is the lower parts of the wall (up to about 6 feet from the
ground) which have flaked, although on the higher parts of the wall, the
paint looks to be cracking and bubbling.

The mortar underneath is sound - that has not started to crack off the
bricks.

What is the best way to repaint it? Is it just a case of using a wire
brush to get off any loose paint, and then painting with Sandtex or some
other outside emulsion paint? Or do I need to first paint the mortar with
some sort of primer and then paint that with the white paint?

Making white (exterior) wall paint stick to mortar rendering
 

Another thing, have you done the mallet test on the render? If some areas
sound hollow you may need to get the blown render fixed first, and the
joints sealed.
Brian

--

This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
"NY" wrote in message
...
Our house is brick built, with mortar rendering over this. The mortar has
been painted with white paint - I can't tell whether it's plain paint or
whether it has sand in it to give it a texture. That was done by the
previous owners before we bought the house two years ago.

Large areas (patches of several square feet) of the paint has suddenly
started flaking off the mortar - it seemed to begin at the same time (late
last year / early this year) in various parts of the wall. The flakes are
several inches square and quite thick as if many coats of paint had been
applied. It is the lower parts of the wall (up to about 6 feet from the
ground) which have flaked, although on the higher parts of the wall, the
paint looks to be cracking and bubbling.

The mortar underneath is sound - that has not started to crack off the
bricks.

What is the best way to repaint it? Is it just a case of using a wire
brush to get off any loose paint, and then painting with Sandtex or some
other outside emulsion paint? Or do I need to first paint the mortar with
some sort of primer and then paint that with the white paint?