On 25 Feb, 22:15, geraldthehamster wrote:
On Feb 25, 7:53*pm, (Andrew Gabriel)
wrote:



In article ,
* * * * "Phil L" writes:

geraldthehamster wrote:
I've just built a little dwarf wall in the eaves of my dormer bungalow
(we're only talking about a 4 foot right-angled triangle), to close
off a space behind a room. After three days the mortar doesn't look
like it's gone off properly, but is sandy and crumbly. Central heating
pipes run through *this space and under the wall, and I'm thinking
that the warm, dry air has caused the mortar to dry out too quickly
and prevented it going off properly. I'm now considering removing the
wall and rebuilding it. I'd turn the heating off during and
afterwards, and possibly give the occasional mist of water to keep
things wet for a bit.

My question is: how long ought I to plan to leave the heating off, to
be certain I've given the mortar a chance to go off? A day? Two days?
Longer? I know I can wait and see, but in the interests of domestic
harmony I need to plan this against the weather forecast ;-)

You don't ned to take down the wall, the mortar is just awaiting some water
to complete the setting process - I've repointed walls and such likes and
the sun has caused this same drying out - the mortar remains sandy until
it's been wetted down a few times, then it sets as normal.

Also, mortar takes about 6 weeks to fully set.
For the first couple of weeks, you'll easily
brush sand off the surface.

--
Andrew Gabriel
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It wasn't just sand coming off the surface - a knife could be pushed
right into the joints. The bricks could be removed from the wall by
hand. Anyway, I've rebuil the wall now, and turned the heating off at
least for tonight. Given these facts, would anyone like to suggest how
long I ought to leave it off now, to give the mortar the greatest
chance? It's all quite damp at the moment as I wetted everything down;
it's my experience that if it's wet for longer it will set more
slowly, but harder - there must be a point though when the chemical
reaction becomes irreversible?

Cheers
Richard

Just been building walls last couple of days. 6 to 1 mix.
Next day bricks are firmly "stuck", mortar getting hard, but could
push a knife in if you tried.
But I wouldn't give the bricks a yank for a week or so. You get that
urge to "go on, push it, see how strong it is" !
By the way, if your loft is now cold, note that mortar takes longer in
the cold ;-)
Simon.