Dave Plowman wrote in message ...
If the house has solid 9" brick walls made out of yellow stocks, the
bricks themselves are porous. Try weighing a dry one then leave it soaking
in a bucket of water, then weigh again...
Sure, but they're still pretty dense compared to the old mortar between
them, which IME is the weak link. I have often wondered about the BRE
research (which you seem to have re-created in your metal bath:-)) . They
build a wall from yellow stocks and can't get water to travel up it, but do
they tell you anything about the mortar they used? I wouldn't go as far as
to say there's no such thing as rising damp in brick, having seen it with my
own eyes this week on a party wall in the middle of a house, but I still
blame the mortar, I think....


However, try building a test wall say 4 courses high in an old steel bath
etc. Fill the bath to below the height of the first course to simulate
bricks sitting on damp earth and leave. You'll find the damp doesn't rise
to the top. This is why the houses all should have a raised ground floor,
and either a cellar or the ground level reduced within the walls. Most
will also have no plaster at floor level, but a high skirting board spaced
off the wall. So any so called 'rising damp' never makes it to the plaster.

The trick is to try and minimise the amount of rain etc that lands on the
bricks. Good guttering etc is essential, as is good pointing, flashing
etc. At ground level, if you have concrete right up to the walls it's a
good idea to cut this about 9" short and fill with gravel to allow a soak
away. It will also stop heavy rain splashing onto the bricks. A mortar
render a couple of courses high at ground level is also common, but I'd
say this is more cosmetic and to protect the bricks from damage.

--
*Being healthy is merely the slowest possible rate at which one can die.

Dave Plowman London SW 12
RIP Acorn