Both approaches end with a dry basement. They get there from opposite sides of the wall,
and that is the whole of the difference.
Interior waterproofing manages the water
Interior work accepts that water is reaching the wall and gives it somewhere to go. We
remove a section of concrete along the affected area and clean the trench of debris, then
lay a four inch corrugated perforated pipe wrapped in a soil separating sock, and pack
gravel around it so the pipe cannot shift. Bead board goes against the wall so moisture
coming through the block can reach the pipe beneath the floor, and then the concrete is
poured back over the top. The drain carries water to a sump pump, and the pump moves it
away from the house. A dehumidifier holds the humidity down afterward.
Exterior waterproofing stops the water
Exterior work goes after the problem before it reaches the wall. We excavate down to the
footer, clean the foundation wall, and seal the pores in the block with an asphalt material
called Blackjack. Over that goes Bituthene, a second asphalt based material that comes in
rolls and adheres to the Blackjack, and that membrane is the actual barrier. A protective
flex board called Hydroduct goes over the Bituthene so the gravel and dirt cannot tear it
during back fill. Then we back fill and finish with a positive slope away from the house.
Which is better?
Exterior work is the more thorough of the two, because water never touches the wall. But
better is not the only consideration. Exterior work requires excavation, which means access
around the outside of your house, and it costs more to do. On a home with a deck, a
driveway, mature landscaping, or a neighbor close by, that excavation may not be practical
at all.
| Interior | Exterior | |
|---|---|---|
| Where it works | Inside the basement | Outside, down to the footer |
| What it does | Collects and removes water that arrives | Keeps water off the wall entirely |
| Excavation | None outside | Yes, to the footing |
| Disruption | Inside only | Yard, landscaping, hardscape |
| Relative cost | Lower | Higher |
Start with the water, not the wall
Before either method is the right answer, it is worth checking the cheap things. A
clogged gutter or a downspout ending at the corner of the house puts a great deal of roof
water directly against your foundation. Ground that has settled over the years and now
slopes back toward the wall does the same. Carrying that water away, or correcting the
grade, sometimes solves the problem on its own and always makes whatever else you do work
better.
We look at how water is actually reaching your basement before recommending either
method. The inspection and the estimate are free.
Common Questions
Can I do interior waterproofing now and exterior later?
Yes, and on some homes that sequence makes sense. Interior drainage gets the basement usable while you plan for the larger job, and the two systems do not conflict with each other.
Will waterproofing fix a crack in my wall?
It depends on whether the crack is the problem or a symptom. A crack that simply lets water through can be handled as part of waterproofing. A wall that is cracking because it is bowing under soil pressure needs structural repair, and sealing it without addressing the pressure just hides the movement.
Does a sump pump have to run constantly?
No. A sump pump runs when there is water to move, which in most basements means during and after heavy rain or a fast snowmelt. A pump that runs constantly in dry weather is telling you something about groundwater around the house that is worth investigating.
What is the white powder on my basement wall?
Efflorescence. It is mineral salt left behind after water passes through the block and evaporates. The residue is harmless in itself, but it is evidence that water is moving through the wall.
Call us at (865) 675-4177 and we will talk through what you are seeing. The inspection and the estimate are both free.