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

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.

Open House Plan for a Small 20′ Wide House

Sean O'Hara — Thu, 19 Jan 2012 21:00:26 +0000

One of my favorite repeat clients called a few days ago and needed a plan for a small house to go on a 25' wide lot in Denver. The house itself could not be more than 20' wide. The client wanted a plan that would fit and would have 2 bedrooms and 2 bathrooms, all on the main level.

We've done some other small affordable rental house designs for him in the past so I wanted to give him a plan that showed the minimum and keep it in a ranch house without a basement. I drew this quick sketch to show that you don't have to put the bedrooms side by side in a 2 bedroom.I also wanted to give access to the backyard that would be more than 30" wide.

As it turns out, the lot is actually wider than the 25' so we have even more options for the actual plan.

Originally posted 2010-10-14 18:09:22.

De Bruin Virtual Tour

evstudio — Thu, 19 Jan 2012 21:00:24 +0000

There is a Virtual Tour of the De Bruin Duplex on Homestore.com.

This half of the duplex is currently for sale through EV Real Estate.

Originally posted 2008-10-06 16:17:58.

Denver Building Code & Energy Calculations

Sean O'Hara — Thu, 19 Jan 2012 20:59:53 +0000

Beth Freeman called the Denver Building Department to ask about their new requirements for energy calculations on single family residences. We haven't had to submit them in the past, but we'd heard that some builders had.

The word from Denver is that you do not need to do energy calculations on dwellings that are framed with 2x6 exterior walls, only those that are framed with 2x4 exterior walls. They're assuming that you fully insulate the 2x6 wall with R-19 or R-21 insulation.

We typically call out R-21 batt insulation as a minimum wall insulation in our houses.

Originally posted 2008-10-08 02:42:46.

Acapulco Denver Restaurant Sketch

Sean O'Hara — Thu, 19 Jan 2012 20:59:31 +0000

I drew this quick sketch to explain the Acapulco Restaurant design to someone at the housing conference. Its drawn on the back of a sheet of heavily printed paper but it should give you a good sense of how this project may end up looking. The Acapulco will replace the existing restaurant on the southeast corner of Colfax and Yosemite in Denver. More coming soon.

Originally posted 2008-10-14 13:32:27.

Raft Slab-on-Grade Foundation

Jim Houlette — Sat, 31 Dec 2011 21:20:36 +0000

A Raft Slab-on-Grade foundation can be as simple as a 4” thick slab with no reinforcement and a shallow perimeter rib to an 8” thick slab heavily reinforced with deep ribs spaced roughly 10’o.c. The wide range of concrete thicknesses and reinforcement is a function of many things such as soil type, loads, exterior finishes, allowable deflections, climate, and many more factors. The primarily factor that influences the slab thickness, reinforcement and rib sizes of a slab-on-grade foundation is the soil type.

If the soil is a sandy material with non-swelling fines to allow good compaction then the slab-on-grade foundation will be evenly supported, and has a low risk of soil movement. This raft foundation will just need the minimum slab, ribs and reinforcement.

If the soil has swelling material that is susceptible to changes in moisture content then the raft must be designed to resist this movement. The use of reinforced ribs is an economical way to strengthen the slab. Ribs are below the slab and are spaced evenly to create a grid or waffle appearance. This is done in lieu of thickening the entire slab because you gain more strength with depth and will typically use less concrete and steel reinforcement to achieve the same design capacities.

Raft foundations have been used for residential structures, commercial structures and heavy construction structures. The reason for the wide range of uses is simply because the raft slab-on-grade foundation is simple to construct and one of the most cost effective foundations. Typically, little earthwork is needed, sites are leveled, ribs are trenched, reinforcement placed and then concrete is placed. Also, since the raft foundation is just reinforced concrete, access to plumbing can be achieved by removing sections of the slab and then patching as needed. If the slab is post tensioned then accessing the plumbing is much more difficult.

But the raft foundation has its problems as well. On sites with high risk of soil movement the slab can become expensive if deep ribs and heavy reinforcement is needed. That is when a post tensioned slab may become cost effective. In addition, the control of visible cracks in the slab can be difficult. Concrete shrinks as it cures and if control joints are not placed appropriately or sufficient reinforcement is not used the owners may be upset with visible cracks. Cracks caused by shrinkage do not indicate failure, but can be an eye sore and a difficult conversation with the owner.

PROS
Cost effective
Common Construction
Low Tech
Sections may be removed to Access Plumbing

CONS
Limited Design Capacity
Does not respond well to Soil Movement

Learn more about different foundation types.

Originally posted 2009-11-03 10:42:22.

EVstudio Denver Office Location Map

evstudio — Mon, 12 Dec 2011 23:46:29 +0000

NOTE: THIS POST REFERENCES OUR OLD PHYSICAL ADDRESS ON SANTA FE. EVSTUDIO'S NEW DENVER LOCATION IS IN THE EVSTUDIO BUILDING AT 1117 CHEROKEE ST., SUITE #100 DENVER CO 80204

The EVstudio Denver office is located at 771 Santa Fe Drive, Ste 200 in Denver. We are just south of the corner of Santa Fe Drive and 8th Avenue.

If you are arriving from I-25 or 6th Avenue the best way is to take 6th Avenue East while staying in the left lane so that you can turn left on Santa Fe and we're 1.5 blocks ahead on the left. If you are coming from the northeast you'll need to lap the block by taking take 8th Avenue west to Kalamath south and then 7th east to Santa Fe north. The map may make more sense.

Parking is generally available on Santa Fe for two hour parking and on other side streets for extended parking. Our logo is on the door and our office is at the top of the stairs.

You can also find us by looking for EVstudio on Google Maps.

Directions and Map for EVstudio Evergreen Office

Originally posted 2008-10-23 15:55:09.

When is a Stage a Platform in the International Building Code?

Sean O'Hara — Fri, 09 Dec 2011 23:50:03 +0000

One of our current projects is the renovation of the gymnasium at the Denver Montclair International School to add a stage at the end of the gymnasium. The stage area is approximately 1,090 square feet. In the International Building Code a "stage" over 1,000 sf triggers a number of requirements for construction including a standpipe, sprinkler systems, fire separations and stage ventilation.

What we needed to do was have the stage area properly classified as a "platform" rather than a "stage" which makes many of the requirements go away. The difference in the definition is that platforms cannot have "overhead hanging curtains, drops, scenery, or stage effects other than lighting and sound". By removing the main curtain we were able to get the building department to permit the renovation without the additional cost of the additional requirements.

Now, that being said, the purpose of having the stage area reclassified is to more clearly reflect the actual use of the space. I would not advise a client to reclassify it if they intended to use it for full scale productions with a high occupancy. In this case the school is using it for small audiences and small classes and doesn't have any plans for drops or anything that requires the additional code protections.

The interesting battle for another day is about any future curtain. The section about the automatic sprinkler system clarifies that sprinklers are not required on stages where curtains, scenery or other combustible hangings are not retractable vertically. The Denver building department was fine with this section allowing a traveler curtain but the Fire department references the International Fire Code which does not have exactly the same provisions.

Originally posted 2010-07-11 17:18:09.

Denver Survey Requirements

DJ Zehnacker — Mon, 21 Nov 2011 08:02:21 +0000

With the recent department shifts and reorganizing at the City of Denver, one thing seems to be coming up quite frequently with residential remodels, pop-tops, and new construction projects---Survey requirements. In the past, an architect, homeowner, builder, or developer could often get by with an Improvement Location Certification (ILC) to satisfy the building department requirements.

An ILC is not a boundary survey and is essentially the simplest form of a survey that can be provided for a property. Although an ILC does show existing improvements on the subject site, it should not relied upon for establishing fence lines, setbacks, building envelopes, etc.

The City of Denver now requires that all remodels, pop-tops, and new residential projects include what they call a "pin survey" as part of the submittal process. A pin survey is a boundary survey that shows existing improvements. In the survey world this is referred to as an Improvement Survey Plat (ISP). Although an ISP is about three times the cost of an ILC it adds some tangible value to a property because all property corners are located and any corners that are missing are re-set. Therefore, at the end of the day, the owner clearly knows exactly where their property corners lie. In Denver the front property corners are typically set with rebar and a plastic cap with the surveyor's license number and rear corners (because they usually fall at the edge or in the alley) are set with a 1" brass washer with the surveyor's license number on it.

For clarity, below is a brief description of the most common surveys:

IMPROVEMENT LOCATION CERTIFICATE (ILC) – Basic drawing that shows general location of existing improvements relative to property boundary, however, this is not a boundary survey . Depending on size of lot, size of structure(s), existing property corner evidence. Turn around in 48 hours – most completed within 24 hours.

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 16 additional options that can be shown depending the goals of the project, requirements of the lender, etc.

Denver Colorado Architect

evstudio — Thu, 17 Nov 2011 08:11:44 +0000

EVstudio started in the mountains of Colorado just west of Denver and has become known for doing work all over the state. While our Evergreen office is still busier than ever, our Denver office has been in full swing for over a year now. As a result, EVstudio has developed a fine reputation with the City and County of Denver on multiple projects that range from urban residential additions, new single family homes, multifamily projects, commercial office and retail design, restaurants and even schools.

Headed up by Sean O'Hara, the managing principal for EVstudio Denver, we have navigated the many challenges that a wide variety of projects face with various regulations and have had tremendous success with our construction documents during the permitting process. Just recently, we walked the Denver International School (formerly Montclair Academy) project through the building department without a hitch. Kudos to the EVstudio Denver staff and if you have a project in the Denver Metro area and are looking for a great local Denver Architect, there is only one place to call 303-670-7242.

Originally posted 2009-02-12 22:54:22.