What they are:

Basically, a helical pier is a giant screw that you drive into the earth to resist compressive or uplift loads, or both.  It consists of a helix, a shaft, and a bracket of some sort at the top.  The pier can have more than one helix, and the shaft can be solid square steel or a pipe section.

Depending on the size, helical piers are driven with portable or with equipment-mounted rotary drive heads.  The drive head screws the pier into the ground while monitoring how much torque it takes to drive the pier.

How they work:

When a helical pier is driven into the ground, the helix pulls itself and the shaft down through the poor soils at the surface to competent soils below.  Once it reaches an appropriate depth, the competent soils support the helix which supports the shaft which supports the load – feel free to sing a round of “the thigh bone’s connected to the hip bone” here.

Before the pier is actually installed, the engineer looks at whatever soil information is available and calculates an estimated installation depth.  He usually bases his calculation on the Individual Bearing Method.  This method assumes that the pier’s bearing capacity is the sum of the bearing capacity of each helix.  The helix’s bearing capacity depends on helix surface area, helix depth, soil type, soil density, and soil consolidation.

During pier installation, the contractor’s gauges can tell him the installation torque necessary to drive the pier.  Years of testing have shown that drive torque correlates quite well with the pier’s installed capacity.  Different shaft shapes and sizes have different factors, but the basic relationship is well established.  For this reason, the engineer will often also specify a minimum installation torque.

Where to use them:

Piers are appropriate in a number of applications.  If a new structure site has poor soils or undocumented fills to a depth that makes excavation and replacement unreasonable, helical piers can often work well.

If an existing structure has experienced a loss of subgrade support, especially if it is an uneven loss, helical piers can provide an economical way to restore support to the existing foundation.

In high wind/light structure situations, helical piers can also provide protection against uplift.  When the highest helix has reached a depth at least five times its diameter into competent soils, the uplift capacity is approximately equal to the compression capacity.  Pier shaft, extension, and bracket connections must obviously be detailed so they will sustain tension.

Please call us if you think your project may benefit from helical piers.  A short (and free!) phone call may save your project a lot of money.

Tips for photo shoots on appraisals, HUD inspections and engineering reports

If you’re an inspector, appraiser, contractor, architect or engineer, likely you will be required to provide photographic backup for your contract or report.  Although the task may seem intuitive, the photo backup may not be up to scratch if the task is taken lightly and the focus of the shoot is haphazard.  This article is meant to provide some insight into these tasks so that your photos are just right every time and will provide the important information required for the documentation at hand. The following are tips for successful photo documentation.

Understand what the end user needs to see – If you are commissioned to shoot a property or buildings for others, ask them specifically what they need for the report before you go out to the site. Take enough photos to do the job. Err on the high side; too many photos are better than too few – digital film is cheap!
Appraisers and others need the big picture inside and out – Provide wide angle views of the site from the street or driveway at a distance that allows the viewer to feel they are there and can see what you see.  Then shoot from a distance that clearly shows the whole view of each side of the building or construction progress. If required to document an interior, take pictures from far enough back to discern what is being shown. Be aware of the environment; consider things like light levels and glare, dark or light surfaces, then take appropriate steps to get the light and depth of field to an acceptable level. Do adjust your automatic camera for dimmer interior conditions.  Check the flash taken photos for acceptable clarity and depth.

Engineering reports for lenders or contractors – These reports are for entities that want the general condition, or the condition of specific areas of a building or site photo documented.  Get a scope of work (unless the project is self-generated), and fully understand the assignment before you start.

1. Good photographs need to be clear.  Delete blurry shots and take them again, look at the image on your cameras screen and decide if it reveals what you intended.
2. Think macro to micro.  When documenting identified damage or the construction progress of something, start far enough away for the viewer to understand the context in which the photo is taken, and then move in closer to get more detail.  Lastly, an extreme close up may be in order to show a certain condition, but these shots are meaningless if your photo doesn’t convey the context in which they are located.
3. Map your photography.  Provide some form of the following: label the photographs, provide descriptive list of the photos describing each in order, draw a plan depicting where you were standing when the shot was taken and label appropriately.
4. Use a computer program that allows the photos to be easily copied, enlarged, light adjusted or otherwise modified.

Specific Technical Photos Applications:

Engineering reports:

These are commonly initiated by lenders, appraisers and others.  What these entities want to know is if the building is structurally sound and to see if there is any structural damage present or to have non-typical specific conditions documented for report, repair, or code compliance.

Photograph the following:

• all sides of overall building;
• the site conditions around and against the building to reveal drainage patterns;
• general view of possible exterior damage first, then medium close (3’ to 6’ away), lastly the most revealing close up;
• matching areas of (possible) damage on the interior, report or shoot the area damaged or not;
• foundation condition in basement or crawlspace.  Fully document cracking, sagging or leaning elements;
• bending, leaning or sloping elements.  Use a straight edge in your photos to show the condition;
• map or label the photographs using cardinal directions or other orientation in your descriptions.

Foundation certification inspections for manufactured housing:

These are commonly initiated by lenders, appraisers and others.  What these entities want is a certification that the foundation is of the permanent type that specifically meets HUD requirements. What the engineer wants to see clearly are the elements that make up the foundation system.

Photograph the following:

• all sides of overall building so it can be seen full height;
• the site conditions around and against the building so drainage can be verified;
• porches and additions, their complete assemblies and attachment to the dwelling;
• the skirting extent, materials, footings, and condition – from inside crawl space and exterior;
• all crawl space elements, long views and semi-close ups;
• types and locations of anchors systems – close ups and semi-close ups, if no anchors are present check for a system that may be located along the perimeter skirt that may be hard to see;
• full heights of typical piers including footings if any – also long views showing the numbers of piers and anchors;
• tongues or axels removed and/or present in crawl space

For a copy of this post and to see photographic examples please contact us at customerservice@haymanengineering.com

Q: How do you know what’s wrong in a basement just by looking at it? Don’t you need to take stuff apart to figure out the problem?

A:  We’re geniuses.  Next question!

Just kidding.  We look at a number of physical symptoms that help us diagnose the problem.  Many of the symptoms we use will be the same things that caused the homeowner to call a contractor or engineer in the first place.

We look for:

- doors or windows that don’t work properly

- cracking in walls

- cracking in brick siding

- cracking in exterior foundation walls

- cracking in basement walls

- gaps between dissimilar materials

To risk oversimplifying, a residential foundation’s job is twofold: 1) to keep the home from sinking and 2) to keep soil outside the basement or crawlspace in place.  Almost by definition, if a foundation has problems it’s because it’s not doing one of those two jobs.  Certain patterns of cracking or distress in the wall and its finishes will almost always indicate the particular type of problem in much the same way that a sick person’s symptoms lead a doctor to a diagnosis without surgery.

1) Sinking – or more accurately settlement – occurs when the soil underneath a portion of the foundation is not strong enough to support the weight of the house.  That portion of the foundation settles, and we see doors and windows that don’t operate properly or diagonal cracking in walls as the house racks slightly.

2) Soils outside the basement or crawlspace push in on the foundation wall.  A foundation wall works in this case by being restrained at the top and at the bottom as well as being strong enough in the middle not to bend or break.  Imagine a book shelf full of books – a thick shelf with good supports works well.  A thin shelf bends too far or cracks. A shelf missing a support on either end falls.  In a soil pressure failure, we see inward movement of the top of the wall, horizontal cracking in the middle, or sliding out of the bottom depending on the part having trouble.  We may see some diagonal cracking at the corners of the wall as stresses distribute themselves around the corner in the wall.  We generally don’t see window or door problems because the first floor of the home stays relatively planar.

Occasionally a foundation will exhibit symptoms that are more puzzling, but usually when we see the cracking patterns described above, we can decipher the gross problem without taking walls apart.

There is a very important issue that many lenders and even some engineers don’t recognize, and that is the issue of new construction versus existing construction when evaluating foundations on manufactured homes. Do existing manufactured homes have to meet the same foundation requirements as new construction? The short answer is no!

The required HUD manual is the September 1996 Permanent Foundations Guide to Manufactured Homes which is a design manual for foundations on manufactured homes. The manual was intended to give specifications for foundations on new construction. However, engineers are required to certify compliance with this manual for existing construction. So what standard do they use? Many engineers will require that existing construction meet the same requirements as new construction, but that is not what the manual states.

The only reference to existing construction is a short two sentence paragraph (paragraph 101-2) that states: “The practices recommended in the Handbook are not intended to be applied retroactively to existing sites unless the authority in the jurisdiction considers such application essential for safety and health of occupants. Upgrade of existing anchorages and footings shall meet the intent of the definition of permanent foundation stated herein.”

Let’s look at what this means.

The practices recommended in the Handbook are not intended to be applied retroactively to existing sites

. . . This statement explicitly states that existing construction should not be held to the same standard as new construction.

. . . unless the authority in the jurisdiction considers such application essential for safety and health of occupants. (I am not aware of any authority anywhere in the US that has mandated the PGFMH standards for safety and/or health reasons.)

Upgrade of existing anchorages and footings shall meet the intent of the definition of permanent foundation stated herein. Here is the sentence that causes so much confusion. First, existing foundations only need meet the “intent” of the standards.

Who decides what constitutes “intent?” The engineer does! This is why it is hard to find two engineers who will agree on what an existing foundation needs to be HUD compliant.

Second, that sentence states that “anchorages and footings” shall meet the engineer’s definition of intent. What about the skirting wall and piers? Are they exempt from consideration on existing foundations? Does the engineer have to address only the anchorage and footing and nothing else? Again, it will depend on the engineer.

I have seen engineers run the entire spectrum from “grandfathering” any existing foundation, which is clearly unwarranted, to requiring the letter of the new construction standards, which is also clearly unwarranted.

The “intent” of the anchorage is to adequately tie the home down during expected wind and seismic events. The“intent” of the footing is to adequately support the weight of the home given soil load bearing conditions and frost depth requirements. It is important to choose an engineer who is very knowledgeable about the PFGMH standards. An engineer who is inexperienced in these standards could wind up costing your borrowers thousands of dollars in unnecessary upgrades.

These days the answer seems to be converging to the HUD/FHA standard, which is ironic, because it’s the most confusing, controversial standard out there.  The standard to be used is a specific document, the HUD Permanent Foundations Guide to Manufactured Housing (PFGMH) dated September 1996.  Sometimes it’s given a document number although the number doesn’t appear anywhere in the guide itself.  Should you want a copy, you can download a pdf version from HUD’s website.  However, don’t get too attached to it as HUD has published a new standard, the Model Installation Standard, which should have gone into effect last October, but has been indefinitely delayed.  The PFGMH is primarily a cookbook of HUD approved designs for manufactured home foundations.  The only trouble is that they are universally despised

For example, the most common method of anchoring a manufactured home to the ground is by using galvanized straps and ground anchors, a method accepted by virtually all states recommended by most manufacturers.  The PFGMH prefers to attach the home to the ground through the stack of CMU piers underneath.  To do this, one needs to not only mortar the CMU blocks together, but also (1) fill the voids with concrete, (2) run rebar into the poured concrete footer beneath the pier, (3) add an anchor bolt at the top, and (4) bolt the I Beam to the stack with the anchor (preferably without wood shims).  This is very elegant from an engineering perspective, but extremely expensive from a set up stand point as it means that the piers have to be in place before the home arrives on site, thereby requiring every home to be craned or rolled onto the foundation thereby adding thousands of unnecessary dollars to the set up costs.  If this sounds overly complicated, it is.  In fact, HUD has completely backed off this requirement in the newer Model Installation Standards, but, until they go into effect, the PFGMH must be followed.

What’s a homeowner to do?  Fortunately, there is an escape clause.  The PFGMH allows an engineer to design an alternative foundation from scratch.  He just has to jump through a number of hoops to do so.  The foundation has to do basically three things: (1) keep the home from sinking into the ground, (2) keep the home from heaving due to frost driven soil expansion and (3) protect the home from wind/seismic driven vertical and horizontal forces.  There are a number of ways to accomplish this and we will discuss them in future articles.

Hayman Residential Engineering Services (HRES) is the first company to cater to the engineering needs of the residential housing industry on a nationwide basis. We strive to bring engineering excellence to homeowners, lenders, contractors and others who have had a difficult time finding engineering resources for residential applications. Residential engineering is not a side business for us—it is our area of expertise. We are here to help anyone who has had difficulty finding excellent, timely, and cost effective engineering resources for residential housing. Presently, our technical staff of four full time engineers/architects is available to provide you with the engineering resources you need. We have a national network of over 1,000 inspectors, hundreds of contractors and over 500 lenders to provide whatever service you need from engineering certifications for mortgage qualifications to repair of damage foundations. We have regional offices in South Dakota, Missouri, North Carolina, Mississippi, Arizona and Georgia and are ready to offer services in every state at a moment’s notice.