ᐅ Insulation: Water Ingress Through a Small Hole in Sandstone Basement Wall

Hello, I have a basement with sandstone walls. At one spot, there is a small hole where water penetrates from the outside. After heavy rain, a puddle forms, about 3-5 m² (32-54 sq ft) in size, rarely larger. The water comes from the hills; there are underground water streams, and one of them runs along this corner of my house. The basement floor is approximately 1.5 meters (5 feet) below street level. These water streams have existed for about 10 years because a large excavation nearby changed the underground water flow.

I would like to fill the hole with cement and apply some cement to the wall in an area of about 40x40 cm (16x16 inches), then dry it with a heat lamp. Is cement suitable for this? Sealing the entire wall apparently doesn’t make sense because the rest of the wall is dry to the touch or just slightly damp. There is some minor moisture, but it’s low. Also, sandstone apparently absorbs water.

Can someone advise which materials and tools might be suitable?

Pozzolanic lime mortar or air lime mortar
Regular cement is not suitable
It becomes too hard

I chipped out the old joints with a small hammer. Behind them, there was often sand and soil, which I scraped out and rinsed with water.
Then I packed pozzolanic mortar into the joints. Professionals throw the mortar in – I can’t do that.
I pressed the mortar in with a spatula and a jointing trowel. If you have wide and/or deep joints, you can place small sandstone fragments in between. This should add stability. I first filled the joints, then pressed the stone in.

haydee schrieb:

Trass lime mortar or air lime mortar
Regular cement won’t work
It becomes too hard

I removed the old joints using a small hammer. Behind them, there was often sand and soil, which I scraped out and rinsed with water.
After that, I packed the joints with trass mortar. Professionals throw the mortar in – I can’t do that.
I pressed the mortar in using a spatula and a jointing trowel. If you have wide and/or deep joints, you can insert small sandstone pieces (broken stones) between them. This is supposed to provide stability. I first filled the joints, then pressed the stones in.

Thank you very much. What ratio should the mortar and broken stones have? 2/2 or something like that? Can this also be applied with a cartridge pump, similar to how silicone is used?

What do you mean by the ratio of rubble stones to mortar?

There are mortar pumps that cost money. Then there are fixed nozzles—I would have gone crazy with those. I don’t know how even your stones or joints are. Here, I had actual gaps that kept filling up more and more.

Hello, which stones (small sandstone pieces (broken) exactly) should I use for the mortar filling mixture, and where can I get them?

Hmm, good question.
I used the mortar that was washed out of the joints and also a large amount from the ground.
Use the trass mortar without stones and you’re done.