plaster skim coat: effect of temperature of hairline crack formation
 

Hi all

Over the years, in a previous house, I had several rooms skimmed with a
thin coat of plaster as the original plaster (eighty years old) was
damaged in places. I noticed that in some rooms hairline cracks
appeared in the skim coat over time. It seemed to be correlated with
the weather conditions on the day each room was reskimmed. The room
that had the most hairline cracks was the one that reskimmed during a
heat-wave. Two rooms had no hairline cracks, and had been reskimmed in
during very cold weather in the middle of winter. Another couple of
rooms were skimmed during typical summer weather (20 deg Celsius) and
acquired one or two hairline cracks. Has anyone else noticed this sort
of correlation, if there is indeed a correlation?

thanks

J

plaster skim coat: effect of temperature of hairline crack formation
 

In article .com,
" writes:
Hi all

Over the years, in a previous house, I had several rooms skimmed with a
thin coat of plaster as the original plaster (eighty years old) was
damaged in places. I noticed that in some rooms hairline cracks
appeared in the skim coat over time. It seemed to be correlated with
the weather conditions on the day each room was reskimmed. The room
that had the most hairline cracks was the one that reskimmed during a
heat-wave. Two rooms had no hairline cracks, and had been reskimmed in
during very cold weather in the middle of winter. Another couple of
rooms were skimmed during typical summer weather (20 deg Celsius) and
acquired one or two hairline cracks. Has anyone else noticed this sort
of correlation, if there is indeed a correlation?

Cracks which form while the plaster is setting and walls drying out
could be due to conditions when applied.

Cracks which form weeks or months later are due to building movement.
If your property is 80 years old, it is likely to be built using lime
mortar. Lime mortar is flexible which means the whole house will
routinely move around slightly. This is caused by things like ground
moisture levels causing ground movements, timbers swelling and
shrinking as humidity changes, etc. Original lime plaster is also
flexible and will thus handle the movement without showing it.
However, gypsom plaster is not flexible, and will instead form
hairline cracks. If you reskim a lime mortar house with gypsom
plaster, this is just something you will have to put up with.
I've done this too and I have got some hairline cracks, but paint
has for the most part filled them (I didn't get round to painting
until about 12 months after doing the plastering).

--
Andrew Gabriel

plaster skim coat: effect of temperature of hairline crack formation
 

On 16 Jul 2006 01:17:02 -0700, "
wrote:

Hi all

Over the years, in a previous house, I had several rooms skimmed with a
thin coat of plaster as the original plaster (eighty years old) was
damaged in places. I noticed that in some rooms hairline cracks
appeared in the skim coat over time. It seemed to be correlated with
the weather conditions on the day each room was reskimmed. The room
that had the most hairline cracks was the one that reskimmed during a
heat-wave. Two rooms had no hairline cracks, and had been reskimmed in
during very cold weather in the middle of winter. Another couple of
rooms were skimmed during typical summer weather (20 deg Celsius) and
acquired one or two hairline cracks. Has anyone else noticed this sort
of correlation, if there is indeed a correlation?

thanks

J
On the hot days maybe the PVA dried out before the plaster was
applied.