Subgrade Building Waterproofing

[Harold89]

I am working on a project involving a building that was constructed in the early 80's. The building is located near the base of a hill that reportedly perpetually had water seeping out of it. The building location was reportedly swampy, highly organic. The soils within the hill and the surrounding geology are clayey with some small (<1") sand seams.

We installed several piezometers around the building and identified static water at up to two feet above the elevation of the floor slab. We also saw primarily clay with sand seams in the borings.

Currently, the building experiences water infiltration problems, primarily in the Spring and Summer and after rain events, but at other times as well. My question is what have others used as waterproofing or water control options on a retrofit project. I have discussed installation of a new sheet waterproofing (Paraseal or similar) system and drain tile outside the building, but it will be extremely difficult and expensive to install. I appreciate anyone's thoughts and comments

 

[layfieldman]

Our company has installed flexible geomembranes into a retrofit like you are talking about. Typically 20mil or 30mil product, very flexible (like PVC), inside the basement and bolted to the walls. A second floor is then poured on top of the liner, very thin, and you are done. You do lose some headroom but very little in an area with little to no traffic.

 

[GeoPaveTraffic]

The only option that I would consider to have a high probability of stopping the water would be a drain installed on the outside of the building extending several feet below the finished floor level. Alternately, the trenchs could be installed from within the building.

 

[DRC1]

We have had sucess with bentoite panels systems to water proof manholes. Although we have only used them on the exterior, you may be able to do something similar to Layfieldmans 's sugeestion. However the most effective solution is always to drain the water away from the building as Geotraffic suggested.