Edwardian side alley/side return drainage/damp.

[lomurtnovice]

Hi,

First post but have always found the treads so helpful.
I live in a little Edwardian terrace and need some advice on a damp rear side alley.
We have one damp wall on the inside see image with blue circle however feel this is more likely poor brick pointing which we plan to get redone in lime (everything is cement at the moment) and a leaking gutter which has now been fixed (I am aware it can take a long time for a wall to dry out). However the bricks above the dpc are always wet and the ground is also always wet and we do get a small amount of pooling water but more in the dips of the soil.

I am weighing up what the best thing is to do to try and dry this area/keep the bottom of the walls dry.
We have had a few quotes from landscapers with different ideas.
1. Put an drain along the side of the house wl then paving against it for the water to run off into the drain
2. Dig down to remove some of the clay soil and replace we better draining soil (we would then likely put paving slabs for stepping stones not covering the whole area) and maybe some hessian with shingles around and lots of planting.

I just feel the worse thing for drainage would be to put hard landscaping down there with the slabs cemented in against the drain however I have no experience!

We also have shallow foundations with only one brick between the dpc and the footings which makes me nervous when digging down for the drain or digging in general!

Has anyone tried things already to help with this and have any advice?

 

[Cubist]

Such relatively small enclosed areas such as these are sometimes referred to as 'Dead Air Zones' because there is little to no movement of the air within them. This lack of air movement results in a significant reduction in the evaporation and onward transmission of water vapour from the brickwork of the buildings into the atmosphere. As a consequence water will be retained in the surface of the brickwork for far longer than it might in more exposed areas and, due to the effects of gravity, will descend to the lowest sections of the wall. Your problems may therefore be from this source rather than damp rising from the earth beside these walls.

However, the slope of the land will have a bearing insofar that this area may be affected by run-off from higher ground collecting in this confined area.

As I understand it the affected areas are not paved in any way and the top-soils have merely been covered with gravel. If this is correct then you are right to avoid any attempt to completely pave these spaces and stepping stones would be as far as you should go in that regard. That said, a gravel filled trench or French Drain beside the wall would aid the evaporation process for water descending from the walls as described above and limit the effects of water retained in the earth to lie against the brickwork to induce rising damp.

Beyond this you will also need to address the brickworks pointing problems as well but should avoid using a different types of mortar. If the walls mortar is predominantly lime
then stick with that or vice versa.

 

[lomurtnovice]

Such relatively small enclosed areas such as these are sometimes referred to as 'Dead Air Zones' because there is little to no movement of the air within them. This lack of air movement results in a significant reduction in the evaporation and onward transmission of water vapour from the brickwork of the buildings into the atmosphere. As a consequence water will be retained in the surface of the brickwork for far longer than it might in more exposed areas and, due to the effects of gravity, will descend to the lowest sections of the wall. Your problems may therefore be from this source rather than damp rising from the earth beside these walls.

However, the slope of the land will have a bearing insofar that this area may be affected by run-off from higher ground collecting in this confined area.

As I understand it the affected areas are not paved in any way and the top-soils have merely been covered with gravel. If this is correct then you are right to avoid any attempt to completely pave these spaces and stepping stones would be as far as you should go in that regard. That said, a gravel filled trench or French Drain beside the wall would aid the evaporation process for water descending from the walls as described above and limit the effects of water retained in the earth to lie against the brickwork to induce rising damp.

Beyond this you will also need to address the brickworks pointing problems as well but should avoid using a different types of mortar. If the walls mortar is predominantly lime
then stick with that or vice versa.

Thanks Cubist,

Very interesting about the water coming from above rather than below, no one has mentioned that at all I just assumed they were damp because of the wet mud.
Yes at the moment no concrete just mud mixed with the peddles.

When you say a french drain beside the wall, at what level would that sit with our shallow foundations? Would it sit next to the first footing brick or on top of the footing brick. I was told by a structural engineer as our soil is clay there should be a layer of soil on the footing brick to keep everything stable so just trying to figure out where this drain would go.
Thanks!

 

[Cubist]

French drains are typically positioned 1 to1,5 feet from the wall and no more that the depth of the brickwork.