Relieving Hydrostatic Pressure in Basement Construction

Relieving Hydrostatic Pressure in Basements

“Are sump pumps the best way of relieving hydrostatic pressure on basement walls from groundwater ?”

OnlineWaterproofingShop believes it’s best to apply a continuous coating/membrane to the waterside which withstands the pressure on its surface. What to do when you can no longer apply a coating to the water side. Then a cementitious coating like Drizoro Maxseal Foundation or Drizoro Maxseal Flex which withstands hydrostatic pressure is applied to the inside. This promotes the cementitious crystalline process which eventually drys your wall.

relieving hydrostatic pressure by drainboard
Drainage systems are a key component of any below-grade waterproofing job. Here, a dimple drain sheet will direct water to the perforated pipe set in washed gravel at the base of the footing.
One critical component of any waterproofing system is removing water that accumulates around the footing and foundation. Otherwise, the water builds up, and under the pressure of its own weight, will penetrate through the cracks and pores in the concrete walls and up through the floor slab. If there are any flaws in the waterproofing, hydrostatic pressure will ensure they leak.

The solution, of course, is to remove the water. Sump pumps, sheet drains, perforated pipe, and other products are designed specifically for this purpose. But they must work together to ensure the system performs as designed. In new construction, some sort of drainage system is required by code. When properly designed and installed, might last the life of the structure. With existing homes, drainage systems sometimes need remediation and repair due to clogs, inadequate sizing, or other issues.

Relieving Hydrostatic Pressure

Joseph Boccia of Boccia Inc., a waterproofing company in Long Island, New York, has devoted his 40-year career to keeping homes and buildings dry. He explains hydrostatic pressure using an example of pushing a beach ball into the water and feeling the resistance.


leaking-block-basement-wall-cementitious-membrane, seal rising damp out

In a properly waterproofed basement, drainage layers prevent water from accumulating around the foundation. He says, “This is an example of hydrostatic pressure exerted on the ball. Without this phenomenon, the overwhelming force on water is gravity which is forcing it down into the ground where there would be no reason for it to make a right turn into a basement. If the basement is surrounded by saturated soil hydrostatic pressure is created. Which forces the water into the basement envelope. The trick is to drain the sub-soils so the basement isn’t sitting in water and the hydrostatic pressure isn’t a pesky problem.”

relieve water pressure, don't just waterproof it...Drizoro it!

When you can’t drain the soil of water to relieve hydrostatic pressure in your and your basement is sitting in water then you need to Drizoro it..

The Problem to Relieve Hydrostatic Pressure

This pressure can exert enormous forces. Four feet of water exerts nearly 300 pounds of pressure per square foot (ca 12.65 Kgs / m²) of the wall, and a basement footing with ten feet of saturated soil above it must withstand 600 pounds per square foot (ca 25.3 Kgs / m²).

Don Williams, vice-president of engineering at Blue Angel Pumps, says “It’s physics. It’s like taking a bucket and forcing it into a swimming pool. If there’s a hole in the bucket, the water will find its way in. It’s the same with houses, and the bigger the basement, the more hydrostatic pressure there may be. It will find cracks in foundations, it will find gaps in expansion joints, it can exploit the porosity in concrete.”
A waterproofing membrane, under these conditions, is typically inadequate. Under pressure, water will find a way through poorly sealed seams in sheet membranes and areas of inadequate millage in spray-applied products.

Says Williams, “Rather than seal a basement against hydrostatic pressure, it’s more efficient and more cost-effective to relieve that pressure.” He continues, “The larger the structure, the more difficult it would be to seal it up completely. Rather than fight the pressure, it’s almost always better to relieve, control, and manage.”


Source: Relieving Hydrostatic Pressure


Whilst the OnlineWaterproofingShop Team believes the keeping water out of your subgrade walls is most effective. Concrete structures are porous.

Waterproofing waterside is the ideal or best solution. Unfortunately it is not always possible. But installing a sump pump in a basement will create a weak point.

Disadvantages of a Basement Sump Pump Install

  1. Allow another point for water entry.
  2. presence of a dampness allows mould to grow.
  3. cutting the hole or drainage channels around the basement may expose reinforcement.
  4. corrosion of reinforcement creating concrete spalling.
  5. chemical erosion of unprotected concrete as fresh water continually runs through the wall.
  6. Physical damage caused by fresh water flowing through any crack or porous area in the slab.
  7. Failure of the drainage system inside or out.

NO you sayTake NOTEThe Grand Canyon was not formed in a day?

The idea behind fitting a sump pump is born out of ignorance. The mentality “if you can’t stop it, pump it out” is steeped in danger!

In the first instance you need to break into a reinforced concrete base. The slab has been specifically designed to take the loading. Especially in lift shafts and possibly other areas of the building. This raft (slab) WILL NOT be designed for someone to come along and cut a hole into it. Which will invariably involves exposing the steel reinforcing or worse cutting through it.

Far better to lock out the water from the structure. This is best done from the exterior/water side. However just relieving hydrostatic pressure drilling and pumping just creates more problems. Negative/interior side waterproofing is the next best solution.

OnlineWaterproofingShop Team

When your membrane fails on the water side and it isn’t possible to be relieving hydrostatic pressure. Then watch how a dry wall is achieved with Drizoro Products in the video below Further information on how masonry wall drys is found here – cementitious crystalline process

Drizoro withstands more hydrostatic pressure than the blockwork would before crushing. The crystalline growth promoted by sealing with Drizoro eventually drys the wall preventing further damage to reo and the cement itself.

Relieving hydrostatic pressure
Basement waterproofing systems are an important aspect of a home especially if it is prone to the effects of seepage. The most common solution for hydrostatic pressure relief is a foundation drainage system. A foundation drainage system has four main components: the drainage pipe, gravel or drainage stone, the concrete that covers the gravel and the discharge system that consists of a sump basin and sump pump. All of these elements must be installed for the system to function properly. 

This article promotes internal drainage sump pump. Drainage outside to inside to relieve hydrostatic pressure.

relieve water pressure, don't just waterproof it...Drizoro it!

When you can’t drain the soil of water, to relieve water pressure, in your basement sitting in water. Then you need to Drizoro it.