How to landscape a sandy slope with rocks to reduce house moisture readings?

[bob11]

Hi Everyone,

need help with a solution for a steep site down the other side of our house, causing high moisture readings in the walls.

Very sandy and has a layer of limestone rocks that are not cemented in.

I've partly removed the rocks  planning to remove the rest.

Top two level sections - installing drainage solution with existing and new plastic and covering with existing stones. Water will be piped down the slope. (refer images)

But what to do with the slope.

My concern is anything I do will be a temporary fix and then break down, eg plastic liner ripping.

The source of the water is all surface and want to stop it going into the ground and move it all to the front of the property.
Planning to take out all the stones, remove some sand from the left side, to create a slope away from the house.

Relay the stones and cement all the stones to create a seal/hopefully keep the sand dry.

Against the side of the house: I don't want to put stones right up to to the side of the house/damage the wall,  plan to have a gap of a few inch's and fill with cement with water proof additive,  then a bead of sika.

What I've suggested sounds okay or anything else you would consider?

Would you cover the whole site with plastic before laying the rocks?   

What plastic is not going to rip apart and if I did put a plastic down, it would help the rocks slide down in time/crack the cement?

Would be nice to seal the house wall but its too deep, 3 meters or more at the top and at the bottom 1.5m to the pad. ( no existing seal from what I can see - build in 1975 approx)

(The other side of the house is similar - but has already had the rocks cemented, with multiple crack repaired over the years and I will be repairing as recommended in the forum with sika along the edge)

Thankyou for any suggests that can help me fix this challenge.

[JacobZ]

Hi @bob11,

Some more context for a few things would certainly help.  Allow me to ask a few questions to help myself and our readers understand what is currently happening.

Do the second and third photos show the top of the slope or the bottom behind the location where you were standing to take the first photo?

Where are you experiencing the most moisture in the wall?

Is the existing black plastic coming up from under the concrete footing of the house?

Where do these drainage channels expel water? 

Is the aim to emulate the slope on the other side of your house that can be seen in your post titled How to seal cracked retaining wall?

If so, I would start by, as you've mentioned, excavating the sand on the left side of Image 1 so that it slopes away from the house. 

I would then add a thin layer of drainage gravel, around 5-10mm thick, over the sand and compact it with a tamper. This thin layer is there to help lock the sand in place and prevent erosion. 

I would then lay builder's plastic over the slope and add a thicker layer of drainage gravel, around 50mm thick and once again compact it with a tamper.

You should then attach 10 x 100mm Abelflex Expansion Joint Filler Foam to the wall so the top edge is in line with where your mortar will go. This will act as a protective barrier to prevent damage to the wall as well as cracking in your mortar from expansion.

You can then relay your larger stones over this compacted base using mortar mixed with Bondall Silasec Waterproofing Cement Additive, ensuring you maintain the negative slope away from the wall.

Once the mortar has dried, seal the edge to the wall using Sikaflex Pro+ Polyurethane Sealant like you planned to do on the other side of the house. This sealant should be applied over the top of the Abelflex.

Let me know what you think. There may be other solutions to the issue that a little more context would help us come up with.

Allow me to tag @Nailbag, @TedBear and @Dave-1 for their thoughts.

Jacob

[Dave-1]

Good Morning @bob11 

Subsurface water entering via the ground is a pain 😕 One I know well.

I actually shifted the soil away from my wall, even went wide enough for a path in one instance

Fixing water ingress issues in garage Is the project. 

I went down the path of how and what to use to stop water entering the garage and also the side of the house. Both had watercomeing from outside and ending up under the house 😕

Stormwater rectification stage 1 

So the best way I can suggest to stop water traveling subsurface wise is to creat an air gap between the wall and your side. Even 100mm air gap is enough. I Really like Gabion cages as they allow free drainage through, are strong enough to self support and also look great  

Plastic sheeting against the wall only works up to the point it may be perforated. The rear of the walls has some fine material (I have used upholstery wadding) to stop fines from entering the baskets. You could do a two step or even three step cage up that slope depending on what you want step wise and includ in it a tall airgap on the right handside.

Here is my current project and note that its off the wall and allows free flowing drainage as well.

What was

The purpose built cage

Full cage installed and I have also installed a grate styled drain and pavers across the front of this.

Dave

[bob11]

Thankyou @Dave-1 for information on your solution and this is a great idea. I'm just not sure this will work for me today, but keen to explore for other projects in the future. My challenge is at the bottom of the paving, the sand depth to the house pad is about 1meter and quickly rises at the top of the slope to about 4.5 meters of dirt/to the base of the of the house , I'll add some extra detail to new images and comments in my message, cheers. Bob 

[bob11]

Hi Jacob,

Thankyou for your reply, I like the plan and the details that I had not considered/was aware of, all I knew was I had a big problem to solve.

To help with more detail of the site I have included new images, I think these will confirm the steps you mention to solve the site issues.

I'm unable to seal the whole outer wall of the house due to the depth of the dirt, but planning to remove the majority  of  the surface water down and exit  to a soak well at the front of the property.

Sealing the outer wall - I can probably seal to about a meter below the dirt level.

The aim is to emulate the slope on the other side of your house that can be seen in my post titled How to seal cracked retaining wall?

(Top level) Re: Is the existing black plastic coming up from under the concrete footing of the house? There was some weave plastic under the rocks before, I have installed the top level drainage and extra plastic to the edge of the house.

Thanks 

Bob

[Dave-1]

Afternoon @bob11 

Im just trying to get the information right

Have you had an indication of water comingthrough to under the house?

If you have what are the indications? 

Sandy soil should really be helping the moisture/water head down hill.....

Going through those photos and reading your words raises a question. Is there only one outlet pipe per wall for the drainage behind it? And if so is it supposed to take the water from the grill drain behind the retaining wall as well?

Waiting to hear back but think I know why you have high moisture readings, and wouldnt be doing anything to the side of the houe just yet (as in waterproofing)

Dave

[EricL]

Hello @bob11 

It is difficult to tell if the plastic is originating from the footing of the house, you'll need to manually check and confirm by slightly tugging at the plastic to make sure it is clipped under the masonry. If it is not integrated with your wall, odds are someone has placed the drain matt in the hopes of diverting rainwater away from the house and into the Easy drain channel. To lock the gravel in place and prevent it from spreading about, I recommend using Landscape Lock 2L Concentrated Garden Glue.

If you need further assistance, please let us know.

Eric