I have to build a new wall at right angles to an existing wall that
does not have a DPC. The existing wall is a 9 inch party wall that,
where the new wall abuts, forms part of an outside toilet. The wall
does have 2 rows of blue bricks that may for a rudimentary DPC I
suppose - but I don't think there is a slate DPC in there. The new
wall to be built against this is the outside skin of a new cavity
Since there is nowhere really to lap the new DPC into, what should be
done at the join with the old wall? The wall as a whole is to be tied
in using a wall starter kit, but the instructions say do not use this
below DPC, I guess because as a general rule this would then be
bridging a DPC. I could run the DPC vertically at the interface, but
then the below-DPC part would not be tied to the old wall at all.
What would usually be done in such a situation ?
Be aware that damp rises in the mortar as well as the bricks and no
matter how blue and impervious they are they are prone to dampness
rising in the only continuous connecting element - the mortar. That
having been said because the bricks are not conducting - rising damp
is less prevalent in such structures and significantly so - it is just
that the bricks are not a "complete" dpc as often is thought.
On 20 May, 23:30, firstname.lastname@example.org wrote:
Yes I agree. I believe one reason why a strong cement mix was
recommended in the DPC was to make it more waterproof as well as
stronger. Of course the cement may crack, so too strong a mix is
counter productive. My house (1930s, solid walls) uses strong cement
mortar in the 2 blue brick courses (it does also have slate DPC in the
main house walls), then lime mortar for the rest of the house. Seemed
stange to me. Houses in my area were built in a traditional style
quite late on apparently.
At least with solid walls I don't have to worry about cavity trays
when building an addition at the back of the house !
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