21 Mar Failing wall? Helical tie backs, wall anchors, braces, carbon fiber, manta-rays or counter-forts?
There is much debate when it comes to wall repair methods. The standard answer we give our clients is; go with what your engineer recommends. That being said, people ask us everyday the pros and cons of each product, so I’ll try and give a recap here.
- A helical-tie back is essentially a helical pier (screw pile) installed laterally to anchor a wall to the soil outside a house. You will need a minimum of 12′ – 15′ of set back (distance from your home to the property line) outside the wall. They are quite cumbersome and expensive to install but universally recognized by engineers as the most fail safe method. They are installed with a mobile hydraulic drive head screwing the pier into the soil. Because torque is directly related to capacity, usually tie backs can be installed without soils engineering which can be costly. Usual price range is $1400 – $2000 per tie back.
- A wall anchor is two steel plates, one inside your wall and one buried in your garden which are held together by a piece of steel all-thread. You will need a minimum of 10′ of set back outside the wall. They are installed by driving the rod through the wall with a roto-hammer. Usually, soils engineering is required although we are starting to see engineers use wall anchors without geo-technical advise. Usual price range is $600 – $800 per anchor.
- Braces are usually made of C-channel installed on the inside of a wall to prevent inward deflection where an anchoring solution is not available (usually due to set back concerns). There are different methods of installation (usually specified by an engineer) that may include wall, joist or floor ties. Because they only tie the wall together and usually put extra pressure on internal home components, their use is limited. Usual price range is $500 – $600 per brace.
- Carbon fiber and kevlar straps are a relatively new addition to the foundation repair field. They perform a similar application to braces but are much easier to install and have a very low profile. Usual price range is $300 – $500 per strap.
- Manta rays are the equivalent of a drywall anchor for soil. Unfortunately, we only ever see failing Manta Rays in the Denver region because they don’t often open correctly in clay soil. I would advise against using these.
- Counter-forts are an engineered solution where limited set backs are a concern. They are a large, formed piece of concrete attached to the outside of the wall, mounted on a helical pier and voided at the bottom. Essentially they pull a wall towards the outside of the structure. They usually require 4-6′ of set back and can be spaced relatively wide. Usual price is $2000 – $4000 depending on sizing, volume and placement.
We are proud to offer every single solution listed above. There are times and places for each. Many contractors will only carry a few of these options and try to use a “One product fits all” solution. In a time of question, consult a licensed structural engineer with experience in wall failure, not the company salesperson…