Exterior foundation waterproofing
Sealing the foundation from outside keeps water from ever reaching the wall. It's the most thorough repair and the most disruptive one.
For exterior waterproofing, a crew excavates beside the foundation down to the footing, cleans the wall, repairs cracks, and applies a waterproof membrane or coating, usually with a drainage board over it. A perforated footer drain at the bottom carries water to daylight downhill or to a sump. The trench is backfilled with material that drains, and the ground is regraded to shed water away from the house.
When does it make sense?
- You want to finish the basement and need dry walls, not just a dry floor
- The original footer drain is missing, crushed or clogged
- The house is cut into a hillside and the uphill wall takes most of the water
- An old stone or brick wall is losing mortar to water from outside
- The foundation needs to be exposed anyway for structural repair
What makes it harder on Johnstown lots?
Steep yards, retaining walls, porches, concrete steps and houses built a few feet apart. On a hillside, the trench on the uphill side can be deep, and the soil coming out may be heavy clay or broken shale that's tough to reuse as backfill. Many homes can only be dug on one or two sides. A careful company will tell you which walls are practical to do from outside and suggest interior drainage for the rest.
What has to happen before digging?
Pennsylvania's Public Utility Commission says homeowners and contractors must call 811 at least three business days before any excavation, so PA One Call can have underground lines marked. Your contractor should make that call. In the City of Johnstown, repairs and renovations need a building permit, and townships and boroughs nearby have their own rules, so ask who will apply.
Questions worth asking
- What membrane or coating are you using, and how is it protected during backfill?
- Where does the footer drain discharge?
- How will you restore the lawn, plantings and walkways?
- What happens to the plan and price if the exposed wall is cracked or bowed?
What drives the cost?
- Foundation depth and length of wall to dig
- Machine access versus hand digging near utilities and tight spaces
- Steps, patios or walks that must be removed and rebuilt
- Wall repairs discovered once the foundation is open
We don't quote prices. The waterproofing company prices the job after it has looked at the walls, the floor joint, the sump pit and the outside drainage, because the same symptom can need very different fixes. Treat any firm number given over the phone, sight unseen, with caution.
Where we connect you with help
Common questions
Is exterior waterproofing better than an interior drain?
It keeps water off the wall, which an interior drain can't do. It also costs more and tears up the yard. The better choice depends on your lot, your walls and how you plan to use the basement.
Can you do only the wall that leaks?
Yes. Excavating just the problem wall, often the uphill side, is common, with the other walls handled another way or left alone.
Related services
More background: Johnstown basement water guide.
Wet floor after a storm, a crack that weeps, or a sump that never rests?
Call and we'll put you in touch with a waterproofing company that works in the Johnstown area.