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Collapsing stone foundation wall along an embankment (C) Daniel FriedmanSite Factors in Foundation Damage Diagnosis
How to Recognize Building Site Factors Affecting Foundation Condition or Foundation Cracking

  • SITE FACTORS AFFECTING FOUNDATIONS - CONTENTS: How to identify site or terrain factors affecting foundation condition. Building site factors contributing to foundation movement, cracking, or damage. Photographs of foundation crack patterns traced to building site conditions
  • POST a QUESTION or READ FAQs about how building site conditions (drainage, grading, nearby roads, waterways, rock) affect foundation damage
  • REFERENCES
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Foundation damage due to site facors:

This document describes how to recognize and diagnose building site factors that contribute to or perhaps cause various types of foundation failure or damage, such as foundation cracks, masonry foundation crack patterns, and moving, leaning, bulging, or bowing building foundation walls.

Our page top photo shows a bulging collapsing stone foundation wall. It's tougher to see in the photo, but construction of a road quite close to this wall left a steep and narrow embankment which, combined with surface and roof runoff, may be factors in the movement found in this wall.

Types of foundation cracks, crack patterns, differences in the meaning of cracks in different foundation materials, site conditions, building history, and other evidence of building movement and damage are described to assist in recognizing foundation defects and to help the inspector separate cosmetic or low-risk conditions from those likely to be important and potentially costly to repair.



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1. Site Factors Affecting Building Foundations - in Foundation Damage Diagnosis: How to Observe Site Factors Which May Damage a Building Foundation

NOTE: Journal of Light Construction articles are available on CD ROM from the Journal of Light Construction, www.bginet.com, 802-434-4747

Authority

Opinions herein are the responsibility of the author. Most of this material has been subject to ongoing peer review but is without any professional engineering analysis. Home inspections may include the discovery of defects involving life, safety, and significant costs. Home inspectors who are not both qualified and certain of the authoritative basis of their conclusions should obtain their own expert advice from qualified experts.

This work is also based on the author's construction & inspection experience, training, research, and survey of material from ASHI, and from N. Becker, R. Burgess, J. Bower, D. Breyer, A. Carson, J. Cox, A. Daniel, M. Lennon, R. Peterson, J. Prendergast, W. Ransom, D. Rathburn, E. Rawlins, E. Seaquist, and D. Wickersheimer. Some useful citations are at the end of this paper.

Foundation Damage Caused by Nearby Construction or Vibration

Reader Question: How do I assess the risk of soil-transmitted vibration damage to my building foundation due to a neighboring vibration-driven steel pier or seawall?

Soil transmitted vibration damsage to foundation query (C) InspectApedia anon

I found your information on the InspectApedia web site and was wondering if you could give me some insight into a concern that I have. My concern relates to whether a newly poured foundation for a new home with a crawl space may be damaged.

Approximately 3 weeks ago I had a concrete foundation pour. The house is 1100 square feet and the footings are located on a "sand base" on lake [deleted for privacy] . My builder established the footings at building code depths and in hard packed sand. Approximately 2 weeks ago, 5 rows of cement blocks were laid, approximately 5 days ago the outside of the blocks were tarred and approximately 3 days ago the house was backfilled with sand. Now comes my concern.

On Monday, my neighbor installed a "steel seawall" along our property line to stabilize sand movement for when he builds his 3000 square foot house. This was done approximately 10 feet from my foundation at the closest point and 15 feet at the furthest point for a length of 46 feet (that's the length of my foundation).

The device used to put the steel panels in the ground looked like a small excavator of some sort with a flat pounding device that actually vibrated the panels into the ground (sand). The panels were approximately 8-10 feet tall and 12 inches wide and were put at a depth of approximately 5 feet. It took about 30 seconds to drive a panel into the ground. My question is, do you think I need to be concerned about the vibration that passed through the ground towards my house, when installing the panels, to where it could have damage my foundation.

A comparison would be like throwing a rock into a pond. Gravity and force drives the rock down but the ripples go outward. I'm wondering if the ripples would dissipate enough before getting to my foundation. Unfortunately my foundation is backfilled and the walls in the crawl space have 2 inch Styrofoam insulation glued to the concrete block from the floor joists down to the footings. The only area that I can visually inspect is a portion of the footing inside the crawl space.

Sorry for the long email. By builder hasn't any concerns. I can't get any type of answer from anyone else that sways me in either direction. I've attached two photos (not very good for evaluation-sorry.) The photo with people in the foreground can be zoomed for a better perspective. Do you think I should be concerned about my foundation being compromised? - D.R. 10/31/2013

Reply:

Soil transmitted vibration damsage to foundation query (C) InspectApedia anon

It is perfectly reasonable to be concerned whenever site-work is performed close to an existing foundation, as some activities, particularly blasting, can damage existing masonry. Certainly from your photos it is not possible to have an opinion about whether or not the foundation for your own house has been damaged by the driven steel piles.

One could say that the engineer who specified that a steel "seawall" be driven into the ground ten feet from your foundation had some reason to believe that the soils supporting the structure to be built on the site for which he was consulted, along with the very close proximity to water along with other site concerns justified such an extra measure.

The information in your note and photos suggest the following questions to me and would suggest others to someone who had expertise with your particular building location and conditions:

  1. Has your own foundation been damaged by anything since it was constructed? Rather than worrying and gesticulating and arm-waving and speculating, why not have an expert engineer or mason experienced with masonry foundations on sand in your area simply inspect the existing work. IF the foundation moved in any significant way one would expect to see cracking or out of level conditions.
  2. What building codes and zoning ordinances where you are building permit a structural foundation and building to be built just ten feet from a property line and close to water where storm damage risks likely to be significant? Are your and your neighbor's projects code compliant? Are there flood zone insurance requirements and building restrictions?
  3. What are the standard concerns & safe working distances for vibration-driven steel piers and seawalls? This data can be obtained from the product manufacturer and the manufacturer of the equipment used to install it.

Certainly the question of propagation of ground vibration in sand (or other soils) during various events, both man-made and by nature, is one that has received plenty of expert research and study.

Some research citations that you might want to review are just below. These authors make clear that *some* consideration of vibration and damage to adjacent structures, foundations, bridges, pipelines, needs to be considered when driving steel piers or seawalls.

Of the citations I offer below, if you were to choose one, I'd look at either Charles Dowding's or Richard Woods' book, or find a local engineer who has expertise in this matter. I include some citations on sinkhole development as well, for other readers whose structures are built on different soils and conditions than your own.

I understand the anxiety about being asked to rely on a sort of "blow-off" statement like "Don't worry about it" from someone you don't know and who may have conflicting interests with those of your own. But if the installation at your neighbor's property was within those guidelines you should be OK.

Soil-Transmitted Vibration or Impact Damage Estimation References

Construction Vibrations - Dowding book image

Sink Hole Engineering References

Watch out for the OPM problem: By no means should you launch a costly investigation or contentious proceeding before taking some simple investigative steps.

1. Take a quick look yourself, just by eye, at the visible portions of your building's foundation - for signs of heaving, settlement, cracking. Any such, at this juncture would indeed merit careful investigation and repair before building up on the foundation.

2. Ask an expert for a general opinion, more or less like "For vibration driven steel piers or seawall material hammered into the sandy soil in the area where my building is being constructed, what are the recommended distance guidelines between the pile driving activity and any nearby structures?" and "What is your experience with possible damage to nearby masonry foundations when using this installation method for steel components driven into the sand?"

If those answers suggest a concern one would dig further.

In sum, if there is no visual evidence of movement or damage to your structure, and no expert indicates a reason to worry, then most likely it is not cost-justified to do an expensive investigation of the buried portions of your structure. It's a tricky spot to balance, between being prudent and avoiding building up on a bad foundation vs. throwing money at what an un-biased expert is confident is not a meaningful risk.

Beware of the OPM problem - a consultant who spends more of your money to reduce not risk to you, but risk to them that you might later come after them for bad advice. An OPM-burdened consultant figures it's free or cheap for them to spend your money to avoid their risk, having you pay for services or investigations that the consultant would never ever, on their own dime, pursue for the same situation.

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