Exterior foundation waterproofing

Exterior work stops water before it touches the wall. It is the larger job, and on a narrow lot the first thing to settle is whether there is room to dig at all.

Call (973) 555-0118

You will be put through to an independent local waterproofing company. Calls may be recorded.

A foundation wall dug out on its outer side, seen in section. The dotted line is the edge of the dig and the heap on the lawn is the soil taken out. The green band is the coating on the wall, and the row of studs is the drainage sheet laid over it. Water moving through the ground (blue arrows) meets the sheet, runs down it to the ringed pipe in clean stone beside the footing, and is led away. The basement, on the right, stays dry.

The sequence

Dig
Soil is taken out along the wall, down to the footing. A small excavator does it where it fits; otherwise it is shovels.
Clean and patch
The exposed wall is scraped or washed. Cracks and open joints are filled so the coating has a sound surface.
Coat
A rubbery membrane is sprayed, rolled or stuck on, from the footing to just above the final soil level.
Protect and drain
A dimpled plastic sheet goes over the membrane. It shields the coating from stones and leaves an air gap that lets water fall.
Pipe
A perforated pipe wrapped in stone and filter fabric is laid beside the footing and run to an outlet.
Refill
The trench is filled in layers and the surface is shaped to fall away from the house.

What gets torn up

Whatever stands along that wall comes out: shrubs, a walk, steps, part of a deck or a strip of driveway. The dug soil sits on the lawn for the length of the job. An air conditioner, a gas meter or an oil fill pipe on the wall has to be worked around or temporarily moved by the right trade.

Where two houses stand a few feet apart, a machine may not fit between them and the open trench will sit next to the neighbour's foundation. Talk to the neighbour before the contract is signed, not after the digger arrives.

When it is worth it, and when it is not

One wall is the culprit

A single wall that faces rising ground or a neighbour's runoff can be dealt with on its own, without touching the other three.

The basement is finished

Digging outside can spare a finished room that an interior drain would tear into.

The wall is being exposed anyway

If a sewer line, an addition or a new walk already means digging there, the extra work is modest.

Water comes up through the floor

Coating the walls does nothing for water rising under the slab. That needs drainage below the floor.

There is nowhere for the pipe to drain

A footing drain with no outlet is a buried bathtub. If it cannot run to open ground or a pit with a pump, think again.

Ask before signing

How deep will the dig go, and will it reach the footing along the whole wall?
Which membrane will be used, and is the drainage sheet part of the price?
Where does the new pipe end: on open ground, in a stone pit, or at a pump?
What goes back in the trench, and who replaces plants, paving and steps?
How will the open trench be shored and covered if it rains during the job?
Who places the 811 request and who obtains any permit?

Exterior work questions

Is outside work better than an inside drain?

They do different things. Outside work keeps water off the wall. An inside drain accepts that water arrives and removes it. Many houses are well served by the inside method at a fraction of the upheaval; a few need the dig.

Can only part of a wall be done?

Yes, if the leak is local, for example below one window or at one corner. The coating should run well past the wet area on both sides.

What time of year suits it?

Coatings need a dry, unfrozen wall to bond. Frozen ground and long wet spells both make the dig harder, so ask the company how weather will be handled in the schedule.