A couple of questions.
1. Doesn't a DPC make a weakness in the wall, or is the material such
that the mortar keys into it for a good bond ?
2. Is it better to use a waterproofed mortar and blue bricks ?
3. When inserting a DPC, is the joint thickness between courses usually
still 10mm, or is it thicker ? I need this for the plans.
TIA,
Simon.

In article .com,
wrote:
1. Doesn't a DPC make a weakness in the wall, or is the material such
that the mortar keys into it for a good bond ?

In theory it is a weakness but this is not usually a concern. You will
find pictures of very long walls without movement joints that have moved
on the dpc over time due to thermal expansion. A dpc would also introduce
a weakness into a freestanding (e.g. boundary) wall.

2. Is it better to use a waterproofed mortar and blue bricks ?

Not usually. You might if it is a garden wall and you really need a dpc

3. When inserting a DPC, is the joint thickness between courses usually
still 10mm, or is it thicker ? I need this for the plans.

Usually still 10mm with modern dpcs

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It may make a theoretical weakness, but not so in practice. The weight
of the wall above gives a good enough bond through friction.

Relying solely on bricks and mortar is not recommended as any slight
movement with crack the joints and the DPC will be useless

The DPC felt should be bedded on 10mm of mortar - smoothed flat with no
voids, and the next couse of bricks/block laid on a normal 10mm joint.

Felt DPCs under copings and parapets may be more problematic, as there
is not much weight on them and so the section of wall above is more
prone to movement

dg

wrote:

A couple of questions.
1. Doesn't a DPC make a weakness in the wall, or is the material such
that the mortar keys into it for a good bond ?

Yes.

2. Is it better to use a waterproofed mortar and blue bricks ?

Your choice. Plastic is chheepp

3. When inserting a DPC, is the joint thickness between courses usually
still 10mm, or is it thicker ? I need this for the plans.

Uusally almost double. Is that really an issue?

TIA,
Simon.

I would agree with dc. The bco cam round to inspect my D.P.C and the
two main criteria were that it be bedded on mortar an most importantly
that it was @made into the existing D.P.C of the building.
What they were looking for wa that the D.P.VC wasn't bridged. In other
words you have to maintain the new with the old. Basically taking your
D.P C plastic into the existing D.P.C.(Which might be slate)/ In simple
terms You have to join the old D.P.C membrane or level with the new
one.
Whether that involve shoving palstic D.P.C into athe old motar joints
at the old D.P.C.




The Natural Philosopher wrote:
wrote:

A couple of questions.
1. Doesn't a DPC make a weakness in the wall, or is the material such
that the mortar keys into it for a good bond ?

Yes.

2. Is it better to use a waterproofed mortar and blue bricks ?

Your choice. Plastic is chheepp

3. When inserting a DPC, is the joint thickness between courses usually
still 10mm, or is it thicker ? I need this for the plans.

Uusally almost double. Is that really an issue?

TIA,
Simon.

The DPC felt should be bedded on 10mm of mortar - smoothed flat with no
voids, and the next couse of bricks/block laid on a normal 10mm joint.
That sounds like the joint could be 20mm, i.e. 10mm mortar, DPC, then
10mm mortar, then brick. Or are you saying the top brick goes straight
onto the DPC ?
Simon.

wrote in message
oups.com...
The DPC felt should be bedded on 10mm of mortar - smoothed flat with no
voids, and the next couse of bricks/block laid on a normal 10mm joint.
That sounds like the joint could be 20mm, i.e. 10mm mortar, DPC, then
10mm mortar, then brick. Or are you saying the top brick goes straight
onto the DPC ?
Simon.

I've yet to see a DPC in a mortar bed that's any thicker than elsewhere in a
wall. Just look around you at the buildings and you can see for yourself. If
you use plastic DPC than the thickness of the plastic is negligible and I
have sandwiched mine within the motar bed so there's mortar above and below.

Paul

wrote:
The DPC felt should be bedded on 10mm of mortar - smoothed flat with no
voids, and the next couse of bricks/block laid on a normal 10mm joint.
That sounds like the joint could be 20mm, i.e. 10mm mortar, DPC, then
10mm mortar, then brick. Or are you saying the top brick goes straight
onto the DPC ?
Simon.

Yes. The DPC joint is 20mm total and it should be 'weather struck'
pointed to distinguish it as a DPC.

dg

The idea is that the DPC is laid on a smooth 10mm bed so that any
settlement will not cause the felt to stress or puncture on a void
beneath it.

If the bed is too thin then the mortar could crack and felt could be
exposed to the frog of the brick or any slightly protruding arris.

It is very common to see only a 10mm DPC joint, but that does not make
it correct. Its just laziness of the bricklayer who has just typically
rolled out the felt directly onto the bricks.

dg