Basement Lowering/Underpinning

The floor is broken apart in sections in order to dig down to the footing of the basement foundation.

Excess soil is extracted manually from the site. Water built up from hydrostatic pressure in the ground is also extracted using a water pump.

Exposed basement walls are cleaned up and debris is cleared from the base of the walls to allow for the installation of weeping tile.

The interior exposed walls are wrapped with rolls of dimpled drainage membrane and secured in using washers and special concrete nails.

Perforated drainage pipe is installed around the perimeter of the foundation wall under the drainage membrane to help distribute water away from the foundation to a drainage source.

Rows of trenches are dug up to fit the 3-inch perforated drainage pipe that will run underneath the poured concrete floor. These drainage pipes will run across the room to collect and move water to a floor drain or sump pump to discharge the water.

The weeping tile is laid down and connected to the wall weeping tile using connector pieces to create a full drainage system running through the basement.

A layer of 3/4 inch gravel is spread out evenly across the room for further drainage capability and to cover up the drainage pipes.

Once the 3/4 gravel is spread evenly, the interior waterproofing job is finished. Now the basement is waterproofed and ready for interior finishing.

Sometimes while underpinning, steel columns are needed for safety and to support the load of the floor above.

Once benching and the necessary measures have been done to make the room structurally sound, then the support columns can be taken out.

Example of a spot along the basement foundation wall where benching will be required.

The underpinning crew will dig the mount of dirt down to prep the wall for benching.

After the mound of dirt on the foundation wall has been dug down and cleaned, then the underpinning team is ready to fill that hole along the basement wall with cement and complete the benching process on this spot of the foundation wall.

Stone foundation wall being underpinned and prepped for benching

Underpinning completed

Sections of wall being poured for underpinning: Engineer specifications

Concrete poured wooden form for benching system

Form created for benching: Rebars put in

Wooden forms put into place for underpinning

Creating a form with steel bars to create a very strong bench: Internal benching

Forms installed: External benching system

Installing benching system sections at a time: Internal benching system

Concrete poured and smoothed to create a good looking bench: External bench

Bench and wall waterproofed once concrete has hardened: External bench system

Pouring concrete in the forms

Concrete poured in benches: Internal bench system

Concrete poured and dried. Benching is complete: Internal bench

Photos Video

If you are looking for a more livable space in your home, the basement is the first place you should look. But what if your basement is unfinished or needs to be lowered to provide a comfortable space for your family? This is where the process of basement lowering or underpinning as it is commonly known as is important for expanding your living space in your basement. This type of basement foundation repair has waterproofing companies dig down to the footing of your house and maximize the height of your ceilings all while strengthening the base of your foundation walls. In many older homes, the basement was never meant to be a living space with low ceilings and exposed ductwork reducing the amount of headroom. Basement lowering is definitely no easy feat considering the number of resources required. However, it goes a long way to expand your living space and will increase the value of your house.

See the underpinning process in action!

Check out our Underpinning Process Video

Cost of Underpinning & Basement Lowering

Find Out More About The Cost Of Underpinning Your Basement – Visit Our Blog Post Covering the Topic

Benefits of Underpinning and Basement Lowering

Also known as underpinning, basement lowering entails digging out the basement floor several feet down. This will add value to your home by ensuring the basement can easily be accessed and used. In addition, underpinning also enhances the integrity of the structure thus uplifting the face of your home. Generally, these basements are about 6 ft high, and lowering the basement by 2 ft for a total of 8 ft for headroom is the desired height.

Here are some terms and processes you will want to familiarize yourself with before you meet with a contractor when it comes to Underpinning

Benching

The benching system is used to create extra living space. The benching system is a sister to the underpinning system, it will allow you to create the same overall height gain but it minimizes your square footage. If the area is finished according to the benching system then this works for many applications. It is a system that is less costly then underpinning and takes half the time.

Benching Process

Basement Waterproofing Benching Process
Concrete poured and dried. Benching is complete.

First step is to have engineer drawings and permits

The concrete floor is removed
The soil is excavated to its proper elevations, pending on the height required will determine how far out from the wall the concrete needs to project
If you lower your basement 1 ft down then this means your concrete bench needs to be 1ft to 1 ½ ft out from interior wall
Once excavated the perimeter is formed for the benching to be poured
The new plumbing is installed, if the elevations for new plumbing cannot be meet then a sewer injector will be required.
The interior drainage system is then installed to waterproofing the property
A minimum of 3 inches of ¾ gravel is placed on floor for base
Then new concrete floor is installed and trowel finished

Underpinning Process

The underpinning system is used for one main reason to create extra living space. This system will allow you to increase the overall height of your basement and the square footage. Most home owners choose to go this route because it gives them the options to use their basement as a rental property which in return will give them a source of income, or to gain a fully finished basement and increase their living space.

Basement lowering and underpinning
Underpinning Completed

First step is to have engineer drawings and permits.

Concrete floor is removed and the soil is excavated to proper elevation
The pins are dug out in sections according to the engineers drawings, typically in three stages
If new posts are required then new footings for posts are installed, which means temporary jacks are installed to support beam
After the first stage of pins is completed there is a 2 inch space between the existing footings and concrete where a 2 inch dry pack grout is installed.
Once all three stages are completed, the new plumbing is installed, if the elevations for new plumbing cannot be meet then a sewer injector will be required.
The interior drainage system is then installed in order to waterproof the property
A minimum of 3 inches of ¾ gravel is placed on floor for base
Then new concrete floor is installed and trowel finished

Find Out More About The Cost Of Underpinning Your Basement – Visit Our Blog

Basement lowering goes a long way in giving your home a complete makeover. However, it is a huge job that will affect the overall structure of your home and you have to do it right. Don’t take any chances or cut corners and make sure the company you choose to do the work has underpinning and liability insurance.

RCC Waterproofing is fully insured and happy to provide customer references.