Homeowner Forum / Construction / April 2007

I'm a DIYer and have done lots of work like this. I suggest you first look
for a damp course, at the foot of the walls, of course. This could be a lead
sheet, slates, felt, etc, depending on when the house was built, and is
intended to keep water from seeping up the walls from the foundation. This
damp course should go all the way around the house, and in most internal
walls too, just above ground level usually.  If there is one, look at the
exterior plaster around the base of the wall. Normally there would be a
break in it at the damp course and the upper part of the plaster would have
a drip edge to drip off the water, that runs down the wall, on a line that
is just below the damp course. I assume that you have deep frosts in winter
which can wreak havoc with the plaster if it is soaked with water when the
frost occurs.

The damp course also helps to keep the water out of the house. If you had no
damp course the water would soak up the wall and evaporate into the inside
of the house, making it an unhealthy place to live.

Generally with plastering, you have a weaker mix - less cement - as you
approach the outside of the plaster layer. Typically, three coats of plaster
are applied but sometimes there are only two - that's what the lowest bidder
will use, unless you specify otherwise in a contract. If your bricks are
clay, you need to have a weaker plaster mix - typically good clean sand with
the right size granules, lime and Portland cement. If your bricks are
concrete, you can apply a harder mix i.e. add some more cement lime and less
lime.

I suggest you visit a local building materials supplier and find the most
competent person available. If you provide a good description he (most
likely) should be able to offer you advice about the plaster mix proportions
for your area. They may also have pamplets that can help you in your work.

About repointing using lime, normally a mix of sand, lime and cement are
used. You can also add a little glue (PVC, I believe) to the mix water and
this will give better bonding in the cracks.Make sure that all loose
material, especially organic stuff, soil, growing plants, etc, are removed
from the cracks and they should be clean when you start. It is best to soak
the cracks a few hours before to start pointing and be sure the crack
surfaces have no surface water in them when you point. They should appear
damp but not glistening.

Hope that helps a little.

RF