DPC too high

[geoffreyP]

Hello
Useful website and have solved a few issues in the past without resorting to
I have a little damp issue, its with a wall not me! Mainly salt deposits on the internal wall, rusty nail showing through skirting boards, damp walls when drilling.
The DPC in my 1930's house is way too high on one side only.
Neighbours path is also too high. I have cleared a 250mm trench but can't easily drill a chemical DPC without clear whole path. Its concrete on top of concrete so just clearing an 10m long channel took all weekend with heavy duty kango.
1st question Can the DPC be installed at an angle as this drawing?

Untitled

• geoffreyP
• 11 Jul 2013
• 1

Note I will not be using a cordless!

What do I do next? Originally I wanted to do an open trench as suggested on this website: Link

Neighbour not too keen as bin will fall in channel as it should be 200mm deep.
Another drawing with enclosed drainage channel and waterproof render. This breaches the DPC and the DPC is below ground, which are both bad.

Untitled

• geoffreyP
• 11 Jul 2013
• 1

Question 2 : is this drawing a good solution? If not what is a good solution?

Thanks for your time

Geoff

EDIT: forgot walls are wet, although drying. Can you do a chemical DPC when walls are wet?

 

[^woody^]

Why do you need to do all that external work if the wall is cavity?

If the problem is a blocked cavity, then you need to sort that out, otherwise the damp will remain

 

[geoffreyP]

Thanks woody

The cavity is full of polystyrene beads so can't see.
I guess trying to poke a stick around might help determine whether it is bridged.

 

[trowlerman]

agree don't see how the path has anything to do with it , damp cant pass through a cavity , try removing a brick to see if cavity is bridged

 

[geoffreyP]

Thanks trowlerman
Took a brick out in 4 different locations about 1 brick higher than where the DPC should be. 1st 2 locations found about 40 to 50mm of wet sand and aggregate in the cavity before hitting something harder. A few part bricks to.
The cavity does not seem deep. Is that normal?
Towards to rear of the house the cavity seems deeper but still some sand. The polystyrene beads were totally soaked here up to level of maybe 150mm above DPC. Again is this normal? Why are they wet?
Your help is gratefully received.

Geoff

 

[Alastairreid]

Clear the cavity and install a couple of air bricks!

 

[trowlerman]

wet sand ? no idea why that's in their, your cavity should be dry and should be hollow to at least 150mm below dpc , clean out all the wet sand and part bricks as this will bridge the cavity and allow damp to pass through from outside wall to inside wall .