Concrete masonry units, also called concrete block or cinder block, are used in many parts of the country to build foundations and basement walls.
CMU foundations have a number of advantages. They are easier to alter than poured concrete and are more versatile than poured concrete. The installed price is comparable in most areas. Most of the basements in the Upper Midwest have CMU walls.
Many of the same reasons poured walls crack include differential settling, backfilling too soon, expansive soils, tree roots, and hydrostatic pressure.
Identify the Problem
The walls crack along the joints. The underlying cause of the problem can be revealed by the pattern of cracks.
Bob Thompson says that the first step in any basement wall repair project is figuring out the cause of the problem. Knowing what to look for and how to read a crack is a big part of that.
Pressure outside the building pushes the wall inward when there is a single horizontal crack in the center two-thirds of the wall. Poor drainage or expansive soils can cause the bow.
At the height of the exterior frost line, the cracks look similar.
It is very common. Most older block walls are bowed in the middle. The easiest ones to fix are the cracks.
There are stair-step cracks that extend across the wall. One part of the home can cause major structural damage if it settles faster than the other. The cracks usually start at a weak point in the wall and run the entire wall. A stair-step crack that is wider than the bottom is a sign of settlement.
It is wise to get a professional opinion on the cause of cracking before making a decision.
When a crack caused by bowing gets within two to three feet of a corner, it will begin stair-stepping to the corners of the room He says that it looks like a settlement crack, but is really a bow problem.
If experts determine that the cracking is caused by settling soils, they can either fill the cracks with foam or fill them with epoxy. underpinning is an option in many cases. The first part of this story explains this topic. Fix Failing Poured Wall Foundations in the Spring 2008 issue of the journal. Steel or concrete piers are attached to the house to eliminateSettling.
Traditional solutions include steel beams or wall anchors exterior basement waterproofing. In the past few years, new technologies have been developed that make foundation repair less intrusive, less expensive, and more visible.
The method of anchoring a steel I-beam to the top and bottom of a wall is called steel beams.
The contractors will bolt the beam to the floor. Others will remove a small portion of the concrete slab, place the beams on the footer, and then pour new concrete around the steel to anchor it.
There is a braced top on the beam.
One intriguing variation of this system is the Gorilla Brace, which claims to push back walls that have been damaged. The Force works on a similar principle.
The Gorilla Brace uses a powerful spring that exerts almost 1000 pounds of force. The wall will eventually be pushed back into it’s original position.
The website says that using a trenching machine or a narrow back hoe outside of the moving wall will allow the wall to be pushed back the same day.
One of the oldest and most reliable methods is the steel beam. Sometimes it’s the most cost-effective solution for the problem. The work is done inside the basement so it can be done all year long.
Homeowners have to deal with steel beams being carted through their home Four to six inches of interior floor space is lost when each wall is braced. They have to deal with the noise of jackhammers, buckets of concrete rubble, and dust.
For serious bows in the middle of the wall, anchors are an excellent option. 10 to 15 feet away from the wall is a buried earth anchor. The large threaded rod is threaded through the wall and attached to the anchor. The wall plate is attached to the interior end of the rod with a nut. The nut needs to be tightened until the bow is reduced.
It doesn’t reduce room size like steel beams do. It has drawbacks. It requires significant excavation around the property and assumes the lot is large enough to hold the anchor. The wall plates have to be exposed for the life of the building so that they can be tightened. Since access doors have to be placed every six feet, basement finishing options have been reduced dramatically. If the wall plate is tightened too much, cracks may form around it.
High-tech carbon fiber is used in the newest method for fighting wall bowed. StablWall, The Reinforcer, and Fortress Stabilization use carbon fiber to stop wall bow permanently. The systems are easy to install, non-obtrusive, and nearly invisible when completed.
StablWall wanted to come up with a carbon fiber product that would work in most of the basement. A 2-foot by 5-foot sheet of carbon fiber was used to fix the wall.
The carbon fiber straps run the height of the room. The thickness is the same as a coin.
The key to these systems is carbon fiber. Carbon fiber can be up to 10 times stronger than steel.
The exterior face of the wall is compressed when a block wall bows. The wall can’t bow if the inside face of the wall isn’t stretching.
The fibers have very little strength, so they have to run parallel to the crack to keep it from closing.
Installation methods are fairly similar for all three of the carbon fiber systems mentioned above.
After determining the location of the reinforcing, and marking it on the wall, the next step is to grind off any paint, dirt, or other debris in the area the strips will be applied.
LaCroix says that they will fill all the cracks and mortar joints with a crack filler. We want to make it easy to navigate.
The back of the carbon fiber product is attached to the wall with a primer coat after the cracks are filled.
That is all that is needed with The Reinforcer. StablWall requires a second coat to be good.
It means more profit for the contractor at a similar price for the homeowner when you factor in the lower cost of labor, the lower cost of tools and manpower hours, and the demand for the product. You don’t need backhoes. There is no crew that hauls concrete buckets. You can work it out.
He states that carbon fiber is in contact with the entire wall, where a steel beam or anchor would not be able to hit the wall for a long time.
The thickness of a dime is the difference between a 4- to 6-inch I-beam and this one. Your options are very wide. You can either furr it out or leave it as it is. Customers think there is a problem if they see beams in a basement. It is less of a problem if they see carbon fiber.
Still, carbon fiber does have limitations.
Thomson says a wall that has bowed in excess of 2 inches is not suitable for carbon fiber. It is not designed to stop settlement.
Settling walls need to be fixed first. Get a structural engineer to look at it. You might have to pier it to fix it.
He says that they still do steel beams. We recommend a complete rebuild of the wall if the wall is tilted in or kicked in.
They will have to address the water issue separately from the reinforcement. beams, anchor, and carbon fiber are not waterproof products.
Unlike poured concrete, block walls have a hollow core that is nearly impossible to seal completely.
The best approach is from the outside.
If outside excavation is not possible, an option is to install an interior drain tile to deal with the water.
Adding structural repair capabilities to their business could increase profits.
Doug Klein is the owner of Klein Basements.
The homes owned by the Erie Metropolitan Housing Authority had bowed foundation walls and had to be fixed.
The carbon-fiber based Reinforcer was proposed by Klein. It took more than a year for the bids to be awarded, but Klein says it was worth it.
He writes that the Housing Authority job was a huge boom for his business. The product is one of the most profitable parts of the business. It works, plain and simple, and customers love it because it is so discreet.