Monday, June 24, 2019
Cochren Foundation
Newsletter
CITY OF CAMBRIDGE
Sewer Installation Delayed due to foundation Failure
A utility company trenched in a gas line adjacent to a property with a stone rubble foundation. The excavation and vibration caused sections of the stone rubble wall to fall stopping all future work on the underground services.
The initial solution was to install timber lagging to protect the wall from the 14’-0” sewer cut within 8’-0” of the foundation. However, the 110” wide narrow laneway precluded drilling rigs from accessing the site.
The solution required shoring up the front of the house, removing parts of the foundation, installing five – 14’-0” deep helix piers (14 kip capacity) and constructing a reinforced concrete foundation wall. Cochren Foundation and Repair provided engineered drawings within 48 hours and completed the work in 3 business days.
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Wednesday, June 5, 2019
Cochren Foundation
Articles
Cochren Foundation & Repairs have been dealing with homes that have water as well as structural issues, including bowed basement walls and house settlement. In the last two years they have been faced with a new challenge, dealing with homes that a going in the other direction – upwards due to frost. In just 5 days they have seen 13 homes that have sustained damage from frost ranging from minor to severe.
We have all seen the effects of frost, a crocked fence post, leaning pillars, a bumpy highway, crooked signs and uneven sidewalks in southern Ontario. However, only in the last two years we are seeing homes lifting up due to a phenomenon called frost adhesion.
Ice lenses form in porous soil and then grow by attracting ground water to them. The movement of water is key to the lens growth and can lead to volume increases well in excess of 9%, the normal volume increase when water changes into a solid.
Frost adhesion is a form of frost heave and occurs under the following conditions:
- Pre-longed subzero temperatures
- Frost susceptible soils
- Abundance of water
In our area, footings are buried 4'-0"feet in the ground to prevent frost from going underneath and lifting the home. With Frost Adhesion, the ice actually attaches itself to the side of the foundation wall forming a bond strong enough to lift the home upwards.
Frost adhesion seems to only effect lightweight, unheated structures such as cold cellars or garages with shallow foundations. Buildings with previously cracked foundation walls from settlement are particularly vulnerable.
The sudden occurrence of a crack is usually accompanied by a large bang being heard if you happen to be there at the precious moment. Plain, unreinforced concrete is very brittle, when the ultimate strength of the material is exceeded, it cracks suddenly, without any warning much like when the ice over a frozen lake cracks.
Distortion is caused by unequal lifting around the garage or cold cellar, causing doors and windows to become inoperable, a 2" difference across the top of a door way is not uncommon. Large step cracks occur in the brick veneer and concrete floors typically heave and crack.
Good News
With luck, the foundation should settle back down with the spring thaw. However, if soil falls into the cracks that formed in the foundation wall by frost adhesion, then the building cannot settle back to its original position, creating a big problem for repair.
Solution
If the home has moved this year or last year from frost adhesion, then it will move again when we experience prolonged cold winters, for this reason it should be dealt as soon as possible.
The remedy for foundations effected by frost adhesion is to effectively remove one of the three contribution conditions by:
Removing the water in the soil
Removing the frost susceptible soil.
Insulated to prevent frost penetration.
No two homes are the same! Finding a guaranteed, cost effective solution creates a new challenge for each and every case. The investigation, must not rule out the foundation had been previously damaged by house settlement. For this reason, initially each case should be treated as both settlement and frost adhesion.
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Friday, May 24, 2019
Cochren Foundation
Newsletter
Freeze-thaw cycles can play havoc with foundation walls that were built with older building materials. Poor mix design & quality control results in a limited life span of these foundations.
Foundations undergoing excessive spalling presents a unique challenge for any contractor to provide a cost effective solution. Accessibility, interior finishes, depth of spalling, the residual capacity of the wall and most important the experience of the crew.
Over the years Cochren Foundation and Repair have successfully restored many spalling foundations.
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Wednesday, April 24, 2019
Cochren Foundation
Newsletter
The foundation walls of the underground parking structure was constructed with unreinforced masonry block. The clay soil adjacent to the wall became saturated as result of poor grading, clogged weeping tile and close proximity to the underground sprinkler system. Over time the expansive clay soils and frost pushed the perimeter wall inwards.
To provide safe working conditions 8’-0” high timber lagging was installed 3’-0” out from the existing foundation wall. This provided enough room for the demolition, concrete formwork, waterproofing, and weeping tile installation.
Between the close proximity to the property line as well as maintaining onsite parking for the 100 tenants created a challenge for the restoration. Cochren Foundation and Repair provided the engineering details for the foundation wall replacement. While working closely with the superintendent and staging the work while tenants were at work allowed Cochren Foundation and Repair to complete this job in 4 weeks.
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Sunday, March 24, 2019
Cochren Foundation
Newsletter
Cochren Foundation and Repair Co. provided a design build proposal to restore 24,000 square feet of underground parking structure. This included precast slab replacement, realigning and reinforcing foundation walls, vertical and horizontal reinforcement, installation of masonry walls and privacy fences.
The design build proposal provided by Cochren Foundation and Repair Co. saved this owner 33% over previous tendered bids.
The 9’-0” high masonry foundation walls were not attached to the precast roof structure. Lateral pressure from backfill caused displacement of the wall.
The roof deck was lifted while the masonry walls were pushed back into vertical alignment. The walls were secured to the precast roof deck.
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