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

Reducing Holdowns Using OSB Exterior Sheathing

Jim Houlette — Sat, 31 Dec 2011 21:20:56 +0000

Tired of all the holdown straps?

You can eliminate many of the metal holdown straps from the upper floor wall to the main floor wall by modifying your OSB wall sheathing layout. When the OSB wall sheathing is continuous over the floor framing section or lapped with the rim board uplift loads can be transferred.

If you are utilizing prefabricated wall panels you can still have the OSB extend to the middle of the rim board. Just have the OSB extend below/above the plates as build in the shop. The only caution is, extra care is needed to prevent the overhanging OSB sheathing from being damaged during shipping.

This concept can also be utilized at the foundation sill plate to help reduce uplift loads that would otherwise require embedded straps such as STHD10RJs. In that situation, cross grain bending is not desired on the sill plate as the load transfers to the anchor bolts. The cross grain bending can be removed from the equation using mud sill anchors (MAS) attached to the exterior face of the OSB sheathing in lieu of anchor bolts. A great solution when utilizing prefabricated walls.

Typically, when building with wood you want many smaller fasteners that distribute the load out evenly rather than a few large fasteners concentrating the load.

EVstudio | Architecture and Engineering | Denver and Evergreen

Originally posted 2009-07-31 00:01:56.

Architecture School on Sundance

Sean O'Hara — Sat, 31 Dec 2011 21:20:44 +0000

The Sundance Channel has a show called Architecture School. It follows the work of a studio at Tulane focused on designing and building a house in some of the more difficult neighborhoods in New Orleans.

Chris and Elicia and I have been watching it and I think it is well done. The project involves real clients and real construction so it is a more interesting show that it might be if it focused more on the traditional studio project. Of course my perspective favors the architecture school experience.

Originally posted 2008-09-12 20:35:47.

Caribbean School of Architecture

Spread Footing Foundation

Jim Houlette — Mon, 12 Dec 2011 23:46:24 +0000

This has to be the most typical foundation type with basement or crawlspace construction. The spread footing design is simple; provide sufficient footing area to distribute the weight of the structure onto the soil. Typically, a 16” wide x 8” concrete footing is used.

The width of the footing distributes the dead and live load of the structure on the soil allowing a typical 8” wide concrete wall to be placed on the footing in lieu of a wide 12” to 16” concrete wall. In addition, the poured footing helps to provide a level surface for the concrete foundation walls. The thickness of the footing will vary due to unlevel soil conditions. The designer should also keep in mind that even if a 12” wide footing satisfies soil bearing, the foundation crew may need at least 16” to allow enough area to set the wall forms on the footings and allow for dimension errors to be adjusted.

A typical spread footing foundation is also referred to as a ‘T wall’.

PROS
Cost effective
Common Construction
Low Tech

CONS
Fails with Swelling Soil

Learn more about different types of foundations

Originally posted 2009-09-13 02:09:33.

Building Season in Colorado, What About Winter?

Sean O'Hara — Mon, 12 Dec 2011 23:46:23 +0000

We frequently have projects and clients who are concerned with the idea of building during a Colorado winter. Snow, ice, cold temperatures and frozen ground can all make building more difficult. With that being said, in the Front Range cities, like the Denver metro, we can generally build year round without many weather delays. As you get into the mountains the delays become more frequent and if you have the luxury of picking your time for building it certainly makes sense to work around the winter.

There are techniques for doing work with frozen ground and cold temperatures, you can tent, you can change your concrete mixtures, you can use blankets to thaw frozen ground, but they do have cost premiums. At the same time, the price of waiting for the spring can also add cost to a project.

Of course the other thing that we all know about the weather in Colorado is that its always changing and hard to predict. You can have a December where the snow doesn't melt, or a March with no snow or a May where it rains almost every day. In any schedule you should plan for weather delays but you shouldn't let the winter be the deciding factor in when you build in Colorado.

Originally posted 2011-05-29 00:27:29.

It's Okay to be a Little Shifty

Dean Dalvit — Mon, 12 Dec 2011 23:46:20 +0000

This post is for all of those framers who diligently adhered to a structural framing plan to the letter and wound up with more backout framing than they knew what to do with once the plumber and mechanical contractor had their way with the joists.

According to Weyerhauser, the makers of the TJI joist products...
TJI® joists that do not occur under a joint in the sheathing may be shifted to avoid cutting them for plumbing or other mechanical. Joists other than the single joist to be shifted must remain at their specified locations. Joists meeting the clear spans of the Trus Joist L/480 live load span table may be shifted up to 6” (but not exceeding a maximum spacing of 24” o.c.).

Framers, have your guys lay out the plumbing and heating penetrations through the floor deck so you can adjust the layout as necessary and save yourselves considerable headaches during backout. While it is a bit unorthodox, we like to show the plumbing fixtures on our structural plans for this very reason. We don't always know how the mechanical contractor is going to run his equipment, so it's better to ask twice and cut nothing at all!

Originally posted 2008-08-11 15:05:28.

No related posts.

EVstudio is Builder Friendly – An Example

Kacy Landsittel — Mon, 12 Dec 2011 23:46:19 +0000

An architect must be able to think creatively and a truly successful one considers how things are put together in the field. This requires understanding what makes things easier and more efficient for the tradesmen who build the various portions of a structure. When such information is implemented into the set of plans for the builder, this makes the set of plans very builder friendly.

In addition to knowing the structural capabilities of materials in a building, understanding the logistics and process of construction is priceless for the success of an architect's relationship with a builder. The well rounded experience of the EVstudio team means that builders can count on a top quality set of builder friendly plans.

An example can be found in the set of plans for the Atwell residence and its decorative wood accent features. Framers prefer, whenever possible to use standard angles, like 22.5, 30, 45, 60, and of course 90 degrees. Dean and I worked out this detail where I made the angle of the 6x6 brace pieces 30 degrees from the vertical wall. This is a fairly common architectural detail where this specification of a 30 degree angle cut can make the job of cutting multiple wood members, assembly and installation much easier for the tradesmen in the field while creating less waste. EVstudio always strives to provide a builder friendly set of plans.

Originally posted 2009-09-01 00:01:25.

Separation of Top of Foundation Wall and Adjacent Exterior Grade

Adam Denton — Fri, 09 Dec 2011 23:50:08 +0000

One of the most commonly asked questions to the structural department involved the required distance between the top of a foundation wall and the adjacent exterior grade. The 2009 International Residential Code requires a minimum of 6 inches of separation where brick veneer is not present. The idea here is to provide a buffer zone to help prevent moisture wicking into the timber framing typically framed above residential foundations. Where brick veneer is present this requirement drops down to 4 inches.

The code text reads:

R404.1.6 Height above finished grade. Concrete and masonry foundation walls shall extend above the finished grade adjacent to the foundation at all points a minimum of 4 inches (102 mm) where masonry veneer is used and a minimum of 6 inches (152 mm) elsewhere.

An example of where minimum separation is close, but not met.

Originally posted 2011-04-03 00:01:32.

Differences in Metric and Imperial Reinforcing Bar (Rebar) Grades and Sizes

Dean Dalvit — Fri, 09 Dec 2011 23:50:04 +0000

All Contractors should be intimately familiar with Steel Reinforcing Bar (Rebar) grades and sizes. With materials coming from all over the globe these days, it is ever important to know the comparison between the Imperial and Metric systems for bar grading and sizing. Starting in 1997, CRSI member steel mills have adopted new "soft metric" standards in their grading and sizing.

The charts below should be used to cross reference imperial grades and sizes with metric grades and sizes. Watch out because if your specs are in metric and your supplier is still using the imperial system, you may wind up with some really huge bar diameters on site. As you can see, the old #4 (1/2") bars are now being called out as #13, so be very careful here to avoid these kinds of potentially costly mistakes.

Soft Metric Bar Sizes vs. Inch-Pound Bar Sizes:

Metric Bar Sizes	Inch-Pound Equivalents
#10 #13 #16	#3 #4 #5
#19 #22 #25	#6 #7 #8
#29 #32 #36	#9 #10 #11
#43 #57	#14 #18

Inch-Pound Grade	psi* Minimum Yield Strength	Metric Grade	MPa** Minimum Yield Strength
40	40,000	280	280
50	50,000	350	350
60	60,000	420	420
75	75,000	520	520

* pounds per square inch
** megapascals

For more information, please visit www.crsi.org/rebar

Originally posted 2009-08-17 17:36:51.

What in the World is a Ufer Ground?

Adam Denton — Fri, 09 Dec 2011 23:50:01 +0000

In EVstudio’s structural engineering practice this question comes up almost every week. In contemporary construction, a ufer is a concrete encased ground electrode, which is most often a 20 foot long piece of #4 rebar cast into a foundation wall that will protrude from the top of wall so that the structure’s electrical system may attach to it. Technically this falls within the realm of electrical engineering, but enters the realm of structural engineering because the 2008 National Electrical Code requires an installation observation. Because the structural engineer typically will already need to be present on site at some point to observe the rebar construction in the foundation walls many building departments are happy to pass the additional liability on to the structural engineer and require them to observe and document the ufer installation as well.

The ufer was invented during World War II by Herbert Ufer, who was tasked with finding a cheaper alternative to the current method of grounding explosive ordinance storage structures against lighting strikes. The previous grounding method required driving hundreds of feet of electrical ground into the poorly conductive soils found in Arizona. Ufer discovered that due to the naturally high ph levels in concrete (uncured “wet” concrete is caustic and will burn human skin on contact*) the readily available supply of ions will conduct electricity better than almost all soils. The interaction of steel and concrete provide a better ground than the interaction of copper wire and concrete so it was natural connection to utilize the steel reinforcing bars already required of most foundations.

* The author has first-hand knowledge of the validity of this claim.

Originally posted 2011-04-14 00:07:08.

Fastening to Concrete – Wedge Style Expansion Anchors

Adam Denton — Fri, 09 Dec 2011 23:50:00 +0000

A 5/8" diameter wedge style expansion anchor.

There are many situations were it may become necessary to attach a timber ledger to a concrete wall. It is desirable in many new homes to lower the elevation of the finished floor to make a home more wheel chair accessible. An example of the differences between the finished floor elevations that can be achieved with a framing ledger are shown below. Additionally, when an addition is made to a residential home a timber ledger is installed so that the finished floor of the new construction can match the finished floor elevation of the existing construction while utilizing the existing foundation wall.

Conventional Floor Framing vs. Ledgered Floor Framing

Wedge style expansion anchors work because of the friction forces developed between the studded collar (see photo at top) and the concrete. To begin a typical installation a hole must first be drilled into the concrete. All manufacturer’s instructions for hole size and depth should be followed carefully because the recommendations will vary between bolts sizes and manufacturers. Once a hole is drilled and cleaned the anchor may be driven into the hole with a hammer. The studs on the collar are slightly larger than the widest diameter of the bolt so initial contact with the concrete is only at these areas. Once the bolt is driven to its specified depth a pre-drilled timber ledger may be installed over the bolts. Finally, the nuts (with supplied washer) may be installed. As the nut is tightened, the studded collar with catch on the edges of the hole in the concrete and will be forced onto the wedge. The collar will expand as it is driven onto the wedge creating a greater frictional force against the concrete. With the nut installed to the proper torque the anchor may be safely loaded to the manufacturer’s design specifications.

Originally posted 2010-07-30 23:04:52.