Architecture, Engineering & Planning EVstudio | Denver & Evergreen Architect | Colorado & Central Texas | Blog » Engineering

Don’t Forget to Check your Sump Pit and Pump

Jim Houlette — Thu, 19 Jan 2012 21:00:51 +0000

Your home may or may not have a sump pit. If you have one be sure to check it every few months, especially when you may have heavy rain. Most people forget about the sump pit leaving them open to a good chance of major problems.

When checking your sump pit check for the following items:

Standing water more than 4"
Properly working sump pump, it should turn on when the float is raised
Discharge pipe properly attached with no leaks
Discharge pipe exists the dwelling and extends at least 5ft away from the foundation
Water entering sump pit, is it dripping or pouring in?

Around the Denver area many houses are built with an elevated structural floor. When you are checking the sump pit be sure to check the conditions in the crawlspace. Feel the soil to see if it feels soft below the vapor barrier. Soft or muddy soil is a sign of high water content. Also, check the floor joists for signs of rotation or buckling. If the foundation wall is exposed look for cracks larger than 1/8" wide.

If you allow water to collect in the sump pit it will eventually rise to a level where the water then collects in the perimeter drain. Once water collects in the perimeter drain the foundation is at great risk to move if swelling soil is present. Also, you are exposing your house to potentially flooding during a heavy rain.

Originally posted 2009-12-20 22:44:14.

Types and Design of Wood Trusses

Jim Houlette — Thu, 19 Jan 2012 21:00:42 +0000

Here are some great resources about the different types of wood trusses and how they are designed. If you have any questions about roof or floor trusses please let us know.

Alpine Engineered Products – Builder’s Guide

SBCA – Structural Building Components Association – Truss Configurations

Originally posted 2009-08-16 00:01:36.

Common Land Surveys Available From EVstudio in Colorado

evstudio — Thu, 19 Jan 2012 21:00:39 +0000

EVstudio has a Colorado Professional Land Surveyor as part of our team and provides a variety of surveys to meet our clients' needs. Four of the most commonly requested surveys are improvement location certificates, land survey plats, improvement survey plats and ALTA/ACSM surveys.

IMPROVEMENT LOCATION CERTIFICATE (ILC) – The simplest survey which includes the size of lot, size of structure(s), existing property corner evidence. Commonly requested for real estate transaction, simple and inexpensive. Only marginally useful for design work.

LAND SURVEY PLAT (LSP) – Also known as a boundary survey. Utilized to determine boundary lines and corners, determine encroachments, and/or construct new improvements on your property, etc.

IMPROVEMENT SURVEY PLAT (ISP) – Basically an LSP with some additional information regarding existing observable improvements such as streets, curb & gutter, sidewalks, dry utilities, wet utilities, etc. Can also include easements of record and topography if the client so desires. Utilized for more extensive proposed improvements and as a base for design services.

ALTA / ACSM SURVEY – Pretty much a cafeteria style survey where the client can pick items from an Optional Table A and create his own survey for specific purposes. The base required portion of any ALTA definitely meets the requirements of an LSP and includes some of the elements of an ISP and includes record Title research of easements and encumbrances to the property. Table A consists of additional options that can be shown depending on the goals of the project, requirements of the lender, etc. This is the 2005 version of Table A:

Originally posted 2010-01-21 00:09:38.

Resistance Piers for Economical Foundation Repair

Adam Denton — Thu, 19 Jan 2012 21:00:37 +0000

EVstudio is asked quite frequently to perform structural evaluations of cracked foundation walls. These cracks are often due to settlement. Modern design philosophy (and most geotechnical reports) calls for the original structural engineer to design foundation walls to clear span ten to fifteen feet to account for soft patches of bearing soil or soils that may be become saturated and hydro-consolidate (shrink in volume when wet). Older homes are more susceptible to damage because they were typically not designed with this in mind. This is not to say they were designed poorly, there were just different design philosophies and industry standards at the time they were constructed.

Installed Resistance Pier Bracket

How a resistance pier works is quite simple. First, a steel bracket is fastened to your foundation, typically at the footing. Then a hydraulic ram is installed on the bracket which drives a steel pier into the ground. Using the hydraulic forces in combination with the weight of the structure above, the steel pier is driven down through the softer soils (which are causing the settlement problem) until bedrock or suitably firm soils are reached. Once the pier reaches competent bearing, the foundation is stabilized and in some instances can even be raised back into a level position.

EVstudio works closely with Pinnacle Structural Services in the evaluation of foundation repairs utilizing the resistance piers as one of many considered solutions.

For more information on resistance piers please watch this informative video.

Originally posted 2011-09-24 00:49:33.

Effect of Overdriven Fasteners on Shear Wall Capacity

Jim Houlette — Thu, 19 Jan 2012 21:00:34 +0000

APA Technical Topics - Form No. TT-012A

With the use of nail guns set too high and the speed of construction, many nails are over driven. Most building officials don't seem to notice or comment on this error. But, if they do you might have a lot of work ahead of you to add correctly placed nails or staples when the nailing is too close for additional nails. Before you start adding nails or staples consider that additional nails may cause more harm than good. If the specified nailing is at 4"o.c. or less, adding more nails can damage the sheathing and studs, reducing the shear wall capacity more than if the additional fasteners were not used. APA addressed this problem and issued a simple breakdown on when you need additional fasteners or not.

Please visit www.apawood.org for additional information and other useful technical bulletins.

Originally posted 2009-08-08 22:27:19.

Steel Screw Pile Foundation

Jim Houlette — Thu, 19 Jan 2012 21:00:31 +0000

A deep foundation system that is gaining popularity in areas with difficult soil, contaminated soil and due to its speed of construction is steel screw piles.

At first glance screw piles look like the typical helical pier. However, there are significant differences that make a dramatic change in capacity. First, the screw piles are installed as a single continuous piece in lieu of sections bolted together. Second, the machinery used to install screw piles is larger and capable of producing a higher torque.

The components of a screw pile are simple; a steel shaft, steel helix at bottom of shaft, and a connection plate at the top of the shaft. Screw piles can vary in size to accommodate different design loads. The steel shaft size is a function of axial load, torsion during installation and thickness due to corrosion. The helix is a plate that is shaped just like the threads of a wood screw and engages the soil to distribute the axial load and it locks into place to provide tensile loads as well.

One of the first questions people have is, “How long will it last until failure from corrosion?” There are several factors that go into corrosion of steel; oxygen, moisture, dissolved salts and other corrosive chemicals. Since there is very little oxygen in the soil, corrosion is limited and can be controlled by using thicker material to allow for expected corrosion. The life of steel screw piles can be 50 years to an indefinite period depending on the type of structure and life span needed.

I designed foundations in Stapleton where the site was located over the old terminal and contaminated soil was discovered. If typical straight shaft drilled piers were used the spoils from drilling the hole would have had to been bagged and disposed of properly. To avoid bringing contaminated soil up to the surface steel screw piles were used.

I list a lot of PROS below and for good reason. I have been very impressed with screw piles and the wide range of uses of them. EVstudio was recently visited by Alpine Site Services for a lunch and learn. Mike Oliveira discussed how screw piles are installed and the many advantages to their system over other typical foundation types. What really impressed me was the speed of placement of screw piles. Alpine can place 30 to 50 screw piles in one day!

Another great advantage to screw piles is that they can be placed at an angle to provide bracing and tension resistance that is aligned with the force of the tension. An example is a typical counterfort that braces a foundation wall. You can see the angled screw pile above.

PROS
Fast Installation
Can be Proof Tested
Negligible Uplift Pressure from Swelling Soil
High Capacity up to 500kips
High Tensile Resistance
Made from a reusable material (LEED point)

CONS
Specialized System
Large Equipment
Concerns with Corrosion

Learn more about different foundation types.

Originally posted 2009-10-10 00:21:43.

Construction Update at Homestead at Saddle Rock

DJ Zehnacker — Thu, 19 Jan 2012 21:00:10 +0000

Since construction commenced the week of 7/11, the Homestead at Saddle Rock project has wound down. The experts at Ground Masters worked hard and finished installing the improvements and landscaping around the grading/drainage problem areas.

In addition to new concrete pans, EVstudio Civil Engineering designed improvements to include NDS drainage inlets with 6” PVC piping. Now that they are installed, these drainage units are discrete and aesthetically pleasing. The inlets are hardly noticeable and are accompanied by appropriate landscaping rock.

In the final weeks of the project we continued to work with the contractor to ensure that all proposed improvements were constructed per plan and functioned as intended. The new retention ponds will prevent ponding elsewhere on the property. If there are any heavy storm events like those of this 2011 summer, the ponds are designed with emergency overflow to drain away from existing structures.

Located just off of Arapahoe Road and E-470, these condos are situated adjacent to the Saddle Rock Golf Course. We had the pleasure of working with both the Homestead at Saddle Rock HOA and the property manager (Hammersmith Management).

For more information related to surface drainage adjacent to structures, check out these posts http://evstudio.info/the-importance-of-proper-drainage/ and http://evstudio.info/surface-drainage-adjacent-to-houses/

Originally posted 2011-10-05 14:57:37.

Construction Material – Aerated Autoclaved Concrete

Anthony Ries — Thu, 19 Jan 2012 21:00:07 +0000

Aerated Autoclaved Concrete, or AAC is a building material that has been around since 1914, mainly in Europe, and available in the United States since the mid 1990s. It is, as the name implies, a masonry product and it consists of aggregate that is no larger than sand.

As a building material it is suitable for low and mid rise structures such as single & multi-family homes, churches and hotels. It has also been used in panel form as a cladding material.

AAC comes in block and panel form. Generally blocks are used to create walls and the panels are used to create floors and roofs. In some applications panels have been used vertically in order to create the walls. The structure rests on an appropriately engineered foundation. The interior finish can be plaster or furred out drywall. The exterior is often finished in a breathable stucco or paint.

Advantages of AAC:
Non-combustible
High acoustic insulation, assemblies can reach a STC of 60
Easy to work, AAC can be cut with a handsaw
Comes in familiar masonry wythes
Improved indoor air quality
Light weight in comparison to CMU (concrete masonry units)
No thermal bridging
Up to double the R-value of foam cored CMU
Thermal mass
Manufacturing process creates no waste
Resistant to mold and fungus
Can be used to gain LEED points

Drawbacks:
Product must breathe due to initial moisture content
Lower load bearing capacity when compared to CMU
Can be hard to find qualified installers
Should be finished inside and out.

The cost of AAC tends to be a bit higher material wise. However the lighter weight of the materials can translate into a less expensive foundation. Additionally, with a knowledgeable crew the system can be constructed in less time. This not only creates a costs savings in terms of labor but more importantly time. On a larger project, AAC can reduce construction time by up to a month or more.

As always it is best to explore materials and construction methods early in a project in order to determine what is best for your project, labor market and material accessibility.

Originally posted 2010-04-24 00:01:37.

Straight Shaft Drilled Concrete Pier Foundation

Jim Houlette — Thu, 19 Jan 2012 20:59:49 +0000

When the soil is unstable and does not allow for a typical spread footing foundation a deep foundation that bears on stable soil below is needed. A deep foundation supports the structure by bearing on stable soil below the unstable soil. It may be helpful to think of a house above water supported by columns. The water represents the unstable soil and the columns bypass the water and bear on the stable soil below the water. Some of the earliest deep foundations were built the same way. The Aztecs built walkways over water by hammering logs into the bottom of the lake bed. This is a typical driven pile foundation, but the same principal applies.

There are many different types of deep foundations. In this post I will focus on Straight Shaft Drilled Concrete Piers. But other deep foundation systems include, wood or steel piles, helical piers, caissons and screw piles.

Straight Shaft Drilled Concrete Piers are constructed by drilling a hole into the ground and filling it with concrete and reinforcing. The diameter of the pier varies depending on the load the pier must support. A 10” to 12” diameter is typical for light loads in residential. Typically, a pump truck with a long tube is used to place the concrete directly at the bottom of the hole to displace any water.

The reinforcing is needed to provide a tensile strength for the pier to resist uplift and moment forces. For small residential piers three to four vertical bars are placed the entire length of the pier. As the loads become larger, a cage of steel may be needed in addition to the full length vertical bars.

Drilled concrete piers must be designed to support the applied loads from the structure and the forces from the unstable soil. First, the applied load from the structure is transferred into the pier and the load is distributed into the bearing soil through skin friction and end bearing. With unstable swelling soil an uplift force may be applied to the pier as the soil swells pushing in on the pier. I like to describe this action similar to the water snake or water tube toys. When you squeeze the toy it slips out of your hand. Obviously, concrete doesn’t behave like water, but when the soil pushes in on the concrete pier the soil pushes to concrete pier up and out of the ground. So the pier must extend deep enough into stable soil to resist this force, therefore, creating a tensile force between the stable and unstable soil layers.

The design of deep foundations can get very complex and the design allows for very little forgiveness if done incorrectly. Unfortunately, this has caused many geotechnical and structural engineers to over-engineer drilled piers.

PROS
Minimal labor
Bypasses unstable soil

CONS
Expensive
Subject to failure if incorrectly designed
Does not address basement floor, so an elevated structural floor is typically needed

Learn more about different types of foundations

Originally posted 2009-10-03 00:01:44.

Seismic Testing of a Mid-Rise Wood Framed Structure

Adam Denton — Thu, 19 Jan 2012 20:59:46 +0000

NEESWood Capstone Test Structure

After the destruction caused by the 1995 Kobe earthquake the Japanese government took it upon themselves to construct the world’s largest seismic testing table, often referred to as a “shake table”. This testing facility, called Earth-Defense, was built to its enormous size out of necessity. Space to build new structures is a rare commodity in Japan and it was essential to be able to test large mid-rise (4 to 7 story) structures that maximize usable space while minimizing the building footprint. The Earth-Defense shake table is 50’ x 65’ and can support an astonishing 2.5 million pounds while “shaking” test buildings in three directions at once.

The NEESWood Capstone project shown in this video was conducted last summer to test the viability of wood framed mid-rise structures. Mid-rise structures are more traditionally constructed out of steel and concrete, but with the trend towards “green” construction it is becoming desirable to use renewable construction products like wood in larger commercial, residential and mixed use projects. The NEESWood Capstone project tested a seven story mixed use building consisting of a steel framed commercial (retail) main level and six stories of wood framed residential units. This test building was constructed in its entirety within the walls of Earth-Defense. The test building was constructed with many proprietary wood and steel products along with new NEESWood construction methodologies, all of which being beyond the scope of this article.

The portion of the results this test that was of most interest to me as an engineer was the “real life” forces experienced in the structure. As engineers in school we are handed exhaustive volumes of information that we are expected to accept as “the unquestionable truth”. There is an understanding that all of this information has been determined by hundreds of collective years of expert design experience, material testing and are always in a continuous state of refinement. As an engineering student I accepted that this was the adopted standard practice of my trade, but I always wondered how all the design theory I was being fed related to the real world. Hundreds of gauges were installed throughout the Capstone structure to test the forces actually experienced during an earthquake. It was quite satisfying as a design professional to see that the calculated anticipated forces at play in the structure were very close to those actually recorded.

For more detailed information on NEESWood Capstone project please follow this link.

Originally posted 2010-07-15 00:01:06.