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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.

Steel Screw Pile Foundation

Jim Houlette — Mon, 21 Nov 2011 08:02:27 +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.

De Bruin Virtual Tour

evstudio — Mon, 21 Nov 2011 08:02:23 +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 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.

BIG BIM, little BIM = Good Design

Bill Foster — Mon, 07 Nov 2011 18:39:37 +0000

BIM (Building Information Modeling)

One of my Architecture professors once told me that the materials and methods you use to express your design will also affect the design itself.

For example, building a model out of clay pushes your design towards a more monolithic structure, while using paper tends to lean the building toward a thinner more surface based design.

Even more dramatic is the difference in design that results from not building a model at all. A purely 2D design vs. a 3D approach. Keeping up with time sensitive, budget sensitive projects doesn't often allow for physical models but using the Computer modeling tools we employ as part of our basic design and production philosophy at EV Studio gives our clients big and small the benefits of 3D Design.

So what are these benefits for the client?

The most important is the ability to clearly see what your project will look like.
The designer also sees deeper into the design, or "around the corner" as I like to say. Look around you at buildings and if you look closely you can see where a 2D approach was used and the details just don't quite go "around the corner".
Automation of repetitive tasks: Elevations, Sections, plans and schedules that are linked allow us to explore and tweak the design without the dreaded ripple effect that forces us to work backward into the design and inevitably results in mistakes and lost time in the schedule.

Despite all these advantages many designers often make the mistake of thinking 3D Design or Building Information Modeling is just for big projects. They see the 3D model as an extra service only warranted for large projects. But we see that the benefits for a small addition in terms of design can be every bit as distinct and while there is a little extra time up front, the automation of tasks evens the equation by project end.

Add to those advantages the quick flexibility and intuitive touch of a hand sketch and the client really wins.

On one recent project I enjoyed moving back and forth between hand sketch and computer methods while solving design problems and communicating them with our clients. I let the computer crunch the numbers to produce just the right perspective allowing me to spend my time on sketching out several options for the client to choose from.

Originally posted 2011-06-23 09:45:44.

A Bicycle City Requires Bicycle Infrastructure

John Olson — Mon, 07 Nov 2011 18:39:33 +0000

Many communities are not currently structured to support everyday cycling. However, in a lot of instances it can be as simple as evaluating the importance of vehicular lane width and the approach of just adding paint. Cities along the Front Range of Colorado have bicycle-friendly adjacent venues, including an extensive mountain biking trail system. Cycling is very popular in these areas as a result, but only for recreational purposes. Most of the cities lack the internal city network that make cycling an effective mode of transportation.

Bicycle lanes that begin and end in isolation are as effective as the cliff for Wile E. Coyote.

Cities need to reconsider the importance of bicycling. Similar to a quality transit system and city street network, connectivity is critical. Bicycle lanes that begin and end in isolation are as effective as the cliff for Wile E. Coyote in the old Road Runner Looney Tunes cartoons.

Trail networks and bicycle lanes must have many points of ingress/egress that are connected to other bicycle lanes, trails or streets that are calm enough for bicycle traffic.

Colorado Springs is in the process of improving its bicycle connectivity with the implementation of “sharrows.” Sharrows are streets with bold signage painted on the surface of the street to indicate that vehicular traffic shall yield to the cyclist. The word “sharrow” is short for “share the road”. This is a great step in connecting Colorado Springs with the use of the bicycle and decreasing our dependence on the SOV (single-occupant vehicles).

Equally important to the bicycle lanes, is the need for safe, visible and often sheltered bicycle storage facilities. Fort Carson, directly south of Colorado Springs, has become aggressive in including large bicycle storage pavilions outside of the new barracks on the Installation. This is a critical component of making the Installation bicycle friendly.

For more information regarding bicycle infrastructure and potentially incorporating the infrastructure into your city’s code, see the Bicycling SmartCode Module written by Mike Lydon, Zachary Adelson and Tony Garcia here

Originally posted 2011-06-12 02:09:32.

Architect and Engineer With Same Day Service

Sean O'Hara — Mon, 07 Nov 2011 05:25:22 +0000

When you call looking for an architect or engineer to help you with your building project you may want quick answers. At EVstudio, when you call you're able to speak to a licensed engineer or architect right away and we are often able to arrange a face to face meeting with an architect or engineer within 24 hours of your phone call. With many of the smaller architecture and engineering projects we are able to turn around the letters and drawings that you need within a few days.

Of course for projects with extensive requirements the time line will be longer but we're capable of hitting any realistic schedule.

Go ahead and call at 303.670.7242 or email.

Originally posted 2010-01-08 00:27:46.