Learn about Settlement & Bowed, Bulging Walls with our Interactive Learning Tools -

Click on links below:

View the Interactive Demonstration of the HouseHolder Piering System

View the Interactive Demostration of the HouseHolder Anchor System 

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Answering Your Questions About Foundation Repair

Danielle from Kansas City wrote to Dry Basement® and Foundation Systems with a few questions. Mark Whitehead, one of Dry Basement®'s Professional Engineers, had the answers.

Q. Is it true that by keeping the moisture content of the soil under my house constant, foundation movement can be stopped?

A. This is often true, but movement can be caused by other factors, such as increased load, vibration, or subsurface changes such as plant or animal activity, frost action, or hydrologic changes. Maintaining constant soil moisture is always beneficial, but this can be a major engineering challange itself.

Q. Is piering a permanent fix to water damage, or an ongoing job?

A. Piering is a repair to provide vertical load support, and its permanence is determined by the design and installation approach. Shallow underpinning may provide success, but permanent load bearing strata may require deeper penetration, which can be provided affordably by hydraulically driven structural steel tubing. This is a major repair project that can encounter subsurface complications, so an experienced contractor with the financial resources to manage these issues is important. The need for future piering for other parts of the building will vary from site to site, but proper installation methods should provide permanent vertical stability to the portion of a foundation supported by piers.

Q. What are the different types of repairing- I am particularly interested in piering, but I am not sure how piering compares to other types of repair.

A. Here is an overview of the various methods of foundation repair.

FOR SINKING FOUNDATIONS (Differential Vertical Movement - Settlement)

MUD JACKING - Injecting grout to fill voids or raise a slab.
PROS:
Good for leveling sidewalks, driveways, patios.
CONS:
Will settle again as soil settles.
Not recommended for foundation walls or footings.

ADJUSTABLE JACK POSTS - Steel posts placed in basement under first floor with screw adjustments to allow for height adjustment.
PROS:
Allows adjustment as movement occurs.
Cheaper than underpinning or piering.
CONS:
Does not stop soil or foundation movement.
When movement of soil or cracking damage occurs this is the sign indicating need for adjustment.

UNDERPINNING - Excavating unstable soil beneath a footing, and filling the void with more stable material.
PROS:
If soil properties are known, and unstable soil is shallow, and firm soil is within a few feet, this can be a low cost, successful repair.
CONS:
If soil properties are unknown, weak soil depth may go beyond the repair depth, and future settlement may occur.

PIERING - Bridging through weaker soil to construct a support capable of carrying the required load.
PROS:
Drilling or driving piers is less expensive than deep excavations to build foundations on solid soil.
CONS:
Obstructions below the soils surface may prevent successful installation.
Can cause damage to existing structures.

Friction Piers - Carry load by soil friction of material driven or drilled in place.
PROS:
Cheaper than driving to solid strata.
CONS:
If there is vibration in the soil or changes in the soil load they will compromise this method.
Unstable soil below pier may move and undermine the pier.

Helical Piers - Helical plate welded to steel shaft, screwed into soil by hydraulic drill
PROS:
Cheaper than full depth piering.
Can be installed quickly.
Increased depth improves tension resistance.
CONS:
Soil disturbed by auger action may move over time.
Water may weaken soil resistance.
Soil below helical plate may move.
Not the strongest repair method available because the strength of the system is in the helical plate and the surrounding soil.

Steel Resistance Piers - Structural Steel Shaft driven hydraulically to supporting strata.
PROS:
Driven full depth, through weak soil, resting on stable strata, not subject to settlement.
CONS:
Must be spaced properly to balance and support the required load.

CRACK INJECTION
PROS:
Crack injection is a common and popular method to quickly stop water leaks and improve the appearance. It is much less expensive than structural repairs that reinforce or add load capacity. It can be effective correcting minor leakage if damaging water pressure or active movement is not present.
CONS:
Rarely does crack repair add structural strength to the concrete. If the stress causing the crack is not removed, a new crack will form after the repair is made. It is very unlikely that a crack repair can reverse the damage from differential foundation movement, or prevent further movement.

FOR BUCKLING OR BOWED FOUNDATION/BASEMENT WALLS (Horizontal or Lateral Wall Movement)

Wall Brace Beams - anchored at top and bottom.
PROS:
Quick to install.
Requires no excavation.
CONS:
Puts the entire load of your basement wall on the weaker floor joists, can cause major problems with your floor joists, upstairs walls and carpentry, etc..
Can cause movement on opposite wall, if earth load is unbalanced.
Structural integrity will likely be lost.

Wall plate tied to anchor rod - with helical plate screwed into outside soil, or steel plate anchor buried outside wall.
PROS:
Anchor is independent of floor joist system.
CONS:
Must core large hole in basement wall to insert helix. This will let in water and can further weaken the basement wall.
Obstructions may prevent proper installation.
Anchor strength limited by plate area and soil properties.
Site or soil conditions may allow plate to move.

Steel wall brace system - Structural Steel Wall Brace anchored to Reinforced Concrete Earth Anchor
PROS:
Anchor is independent of floor joist system.
Concrete anchor combines mass and soil friction for increased stability.
Can be sized to fit soil properties.
CONS:
Outside excavation required.
Structural integrity of wall must be sound for this method to work.

Wall Straightening
PROS:
Cheaper than replacing wall.
Improves Structural stability, if wall misalignment is excessive.
CONS:
Outside excavation required.
Structural integrity of wall must be sound after straightening.

High Strength Fiber Strapping - Thin fiber / epoxy strap bonded to inside face of wall.
PROS:
Thin strap material has smaller profile than structural steel.
Anchor is independent of floor joist system.
Requires no excavation.
CONS:
Structural integrity of wall must be sound.
If wall has excessive misalignment, excavation may be needed to straighten wall.
Bond between strap and wall material may fail from moisture and weathering.

Wall Replacement
PROS:
Can address walls that have failed or are too unstable to repair.
CONS:
High cost.
May not change conditions that damaged wall.

Crack Injection (see above)