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Stair Construction Tolerance and Dimensional Uniformity

Sean O'Hara — Thu, 19 Jan 2012 21:00:50 +0000

The 2006 International Building Code calls out the tolerance for how consistent each stair tread and riser needs to be in a set of stairs. The code refers to it as dimensional uniformity. What the IBC states on stair tolerance is that the difference between the largest and smallest riser height and the largest and smallest tread depth can't be greater than 3/8" within a flight of stairs.

With spiral stairs the 3/8" is measured at the 12" walk line.

Originally posted 2011-05-24 00:36:39.

Top 10 Important Things to Know for SIPs

Dean Dalvit — Thu, 19 Jan 2012 21:00:49 +0000

With the growing popularity of SIP designed homes, it is important to know some critical details that are different than traditional stick frame design. Below is a list of what I have developed as important details to consider as early as the pre-design stage as well as tips during construction as well:

1.) The thickness of the SIP wall is a critical factor in determining your layout geometry. Most SIP manufacturers provide panels in both 2x4 and 2x6 varieties, however, bear in mind that those sizes predicate that the 2x4 or 2x6 is sandwiched between the panels. Therefore, your wall thickness to rough structural frame will be 4-1/2" and 6-1/2" respectively. Including the OSB skin is very important to the structure.

2.) The entire sip wall must be supported by the structure below. In frame construction, you typically run the studs to the outside face of the floor deck or foundation, then sheath beyond that. In SIP design, the OSB skin bust be supported and therefore will cause the layout to be shifted by about 1/2".

3.) SIPs panels must never be in direct contact with concrete. No untreated wood should ever come into direct contact with concrete because the caustic nature of the materials in concrete will cause rapid and premature decay in the wood fibers. SIPs panels are no different. In special circumstances, you can have a SIPs panel manufactured with treated skin.

4.) Do not add additional plates above the panel that are less than the full panel width of the SIP wall itself. This is tied to the structural implications in item 1 above, but the entire SIP wall (skin-to-skin) is the structural member, and therefore should be loaded continuously across the full thickness of the panel.

5.) Don't design unsupported horizontal joints in the wall. This is also true with stud framing. You should not introduce hinge points within walls of any height. Instead, in stud framing, you would balloon frame the wall, or in SIPs detailing, you would run the SIP wall full height. Special care must be taken because there are practical limits to the sizes of SIPs panels. The manufacturer should make special recommendations for cases where the walls in the design exceed these limits.

6.) Plan for only continuous 2x's or i-beams for SIP spline connections. Using spliced lumber for these splines will significantly reduce the structural integrity of the wall system.

7.) Provide access holes in the sill plate to allow for electrical wire chase access. Often forgotten, these access points are critical for your electrician. The SIP wall design specific you your building will have more information about the sizes and locations of wiring chases and a little preplanning goes a long way down the road. As a result, it is always a good idea to develop the electrical plans before the SIP wall manufacturing.

8.) Avoid plumbing runs in the SIP wall. This means supply lines, vent stacks etc.. There are special details for these conditions that allow this to happen without impacting the thermal or structural performance, and they must be addressed on a case-by-case basis. Again, planning in the design phase helps to circumvent potential conflicts during construction.

9.) Never overcut the skins for field cut openings and don't cut the skins for electrical chases. These cuts impact the structural ability of the wall to carry the design loads. Wherever possible, have all openings and chases provided in the SIP core by the factory.

10.) Handle SIPs with care!! Protect them on the jobsite from the weather. Provide adequate supprt when storing them flat to avoid deflection. Never lift them by the top skin only. Don't drop them on their corners as they will easily damage.

SIPs offer a great option for many building types and the more you know about how to design with them as well as what to look out for during construction will help to make the design and construction process much more seamless (not to mention painless).

I've also written a post comparing and contrasting Insulated Concrete Forms vs SIPs.

Originally posted 2008-12-15 10:35:09.

ICF vs. SIP…The Debate Continues

The Easiest Place to Find Fire Rated Assemblies is the Gypsum Association Manual

Sean O'Hara — Thu, 19 Jan 2012 21:00:47 +0000

After several projects of fighting with the UL Manual (Underwriters Laboratories) and the International Building Code I discovered that there is a much easier visual way to find fire rated assemblies.

I use the Gypsum Association Fire Resistance Design Manual. Everything is visual and it is generally acceptable to building departments. It contains the most used gypsum fire rated designs and it also contains information on sound ratings for most of the assemblies. Plus it is a free download which the others are not.

The main note is that you need to read the ratings carefully where some of them are proprietary and designed for one manufacturer's gypsum product. In many cases there will be another number for the same assembly from a different manufacturer or a generic product. You can list them as alternates.

In addition you should read the general notes at the front, they tell you about ways that you can modify the assemblies and still maintain something acceptable for the rating. This is important for adding insulation, adding other layers to the assembly or changing the size of framing members.

Finally, if you need a rating that doesn't involve gypsum board then your best bet is probably Chapter 7 of the IBC. That's where I go for concrete and other assembly materials.

Originally posted 2008-10-27 22:27:18.

Interesting Insights on Architecture That Can Repair Itself

Dean Dalvit — Thu, 19 Jan 2012 21:00:46 +0000

Most people don't realize that there is a growing body of research in the world of architecture based on biologic solutions to our built environment. This particular video by Rachel Armstrong from TED.com discusses technologies that are currently being researched that would actually use living organisms to create a limestone foundation underneath Venice's failing wood piling system. It is a completely new way to think about how we may be able to solve problems like this, as well as implement these ideas into new architecture.

The idea of self-repairing architecture can be staggering. I have contemplated exterior sidings that might live and repair themselves similar to the bark of a tree. In fact, I wouldn't mind at all if it even looked like the bark on a tree. With advancements in fields originally thought to be wholly unrelated to architecture, like microbiology and electrochemistry, we may be able to collaborate on our collective ideas to develop a new architecture that relates and interacts with our natural environment in a natural way. In my own contemplations, perhaps there may be some way to graft living bark onto a substrate that could be joined in a system to create such a living wall. Maybe this is something that can be done on site to existing buildings. It would give rise to a tree house with a whole new meaning.

Consider the myriad of other possibilities that might implement living organisms to create a living structure - much in the same way that thousands of species use coral as their home. Instead of growing foliage outside of the exterior skin of a structure, let it be the skin of the structure, or perhaps even the structure itself. Can rigid structures like coral be easily grown on the terrestrial surface? This kind of thinking may give rise to a new and truly organic kind of design. How it would be viewed under our current building code is an entirely different question!

I will be posting more on this topic as I continue my own research, but I encourage a discussion on it to share ideas.

Originally posted 2009-11-10 02:00:30.

Accessible and Smart Rec Center Cabana Design

Matt Svoboda — Thu, 19 Jan 2012 21:00:45 +0000

One of the most important functions of recreation center cabanas in family locker rooms is providing a convenient place for users of all physical ability levels to change in comfort and privacy. As the recreation center cabana concept has become more common, the diversity of target users has increased and the types and arrangements of fixtures has evolved as well. Cabanas now are often larger and better designed to not only accommodate wheelchair users but families and seniors also. Standard clearances and adjacencies are of course observed, but there are other factors for an architect to consider:

The Bench - An accessible bench is required by code for the rec center cabana to be considered a changing room or part of a locker room, and benches of this kind are often misinterpreted. The bench is required to be 20-24 inches deep and 42 inches long minimum, and is required to allow a parallel approach on a SHORT end of the bench. This means that a wheelchair user should be able to position themselves with their back to the wall and slide onto the bench in a manner similar to how they would move onto the retractable seat in a shower. Also, consider using a longer bench (up to 6 feet) if you have the room. Not all of your disabled guests need a wheelchair! For your guests which need assistance getting dressed, a place to lie down fully can be a big help. If you are concerned about using up too much space, make one "deluxe" room and minimize the rest...your users will remember which one it is!

Door swing - Swinging a door out of a room is a common trick when having trouble with required clearances in the room, but in a high-traffic area like a family locker room it is often inadvisable to allow a door to swing out for fear of hitting someone. Try keeping all plumbing fixtures on the wall opposite the cabana door to allow the maximum door maneuverability.

Toilet partition - The biggest eater of space in any accessible area is the turning radius. This can be exacerbated by the desire to have an individual toilet partition in your cabana which allows one family member (a child, for example) to use the toilet with privacy while others use the shower or wash their hands. If you have several cabanas and space is tight, consider using the toilet partition in only the non-accessible rooms, and you'll find there is greater flexibility and convenience for your disabled users, who frequently use the room solo.

Originally posted 2010-02-26 00:01:04.

The Maximum Occupant Load in the Building Code – Not a Maximum

Sean O'Hara — Thu, 19 Jan 2012 21:00:43 +0000

There is a common misconception about the "Maximum" Occupant Load table in the International Building Code. This table list the number of occupants per square foot that you are designing to rather than a true maximum.

As an example, the table lists 100 gross sf per occupant in a business occupancy. If you have a 1,000 sf office then you are designing for 10 occupants. However, the 10 really functions as a minimum rather than a maximum. You must design adequate exiting and fixture count for 10 occupants.

If your space is actually designed for more occupants that's absolutely fine as long as you are following all of the code provisions for more occupants. In this example if your 1,000 sf is a call center with 25 people, then you need to make sure your exiting, plumbing, mechanical and so forth are designed to handle 25. You just have to make sure you don't exceed 1 person per 7 square feet, that's an absolute maximum and very tight quarters. I've never seen it, but the code official can ask you to show a diagram for your increased occupant load.

On the other end of the spectrum, you can actually design for less that the maximum occupant load, but only with approval of the building department, and I've never seen this happen.

The code section uses the phrase "design occupant load" and that is really a more accurate phrase.

Originally posted 2009-09-26 00:01:19.

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 Egress Window Sizes and Operation

Sean O'Hara — Thu, 19 Jan 2012 21:00:41 +0000

I recently posted an article on the rules behind egress windows. I realize that knowing the rules doesn't necessarily mean that you know the most common window sizes for each different window operation. So here are the basics and some links to the Anderson Window catalog as a guide:

Casement windows are minimally 2'-4" wide by 3'-4" high. For many casement windows you'll need to order egress hardware which allows the window to not only swing open, but also swing away. Also remember that the sill can't be more than 44" above the floor so you may end up with a taller window for a head height over 6'-8". Anderson's Casement Sizes

Single or double hung windows are minimally 3'-0" wide by 4'-8" high or 2'-8" wide and 5'-6" high. I've seen a 2'-6" wide by 5'-0" high egress window but not all manufacturers make this window size. Anderson's Double Hung Sizes

Slider windows are minimally 4'-0" by 4'-0". Again, watch the maximum sill height. Anderson's Glider Sizes

I've included the links to the Anderson catalogs because they are very clear which of their windows allow for egress. Many manufacturers will call this out in their size charts. I'd suggest checking the specific sizes with the manufacturer that you intend to use and always specify which windows are intended for egress.

Originally posted 2008-11-08 00:01:41.

Rating of Floors and Ceilings of Exit Enclosures

Bill Foster — Thu, 19 Jan 2012 21:00:40 +0000

(Disclaimer: Code Analysis especially for egress and fire ratings is very building specific and a solution that works for one building may not work for another.)

In a recent project I set about to solve a question that occurs quite frequently in multi-story buildings.

Can you rate the ceiling or “lid” of a stair or elevator enclosure thus avoiding the expense and complication of taking the rated walls to the bottom of the roof? What I found is still somewhat inconclusive. On this building the IBC allows for a rated lid as long as it matches the rating of the vertical walls (IBC 2009, Section 708.12).

The only problem is that ceiling assemblies do not have their own ratings. Only Floor/Ceiling or Roof/Ceiling assemblies are given ratings. This can be handled by making the ceiling of the vertical enclosure into a Floor/Ceiling assembly. If you are dealing with a building type that allows for combustible materials such as plywood in your floors then there are relatively simple assemblies that will work.

If not then the assemblies get more expensive and it may be in your best interest to take the walls of your enclosure to the bottom of the roof deck. This was the case in this building.

That choice brought up another question:

Does the roof have to be rated at the top of a stair or elevator shaft?

The answer on this particular building appears to be no because the IBC only talks about the walls of vertical enclosures being rated and does not mention the top and bottom.

IBC 707.3.2 “fire barrier separating building areas from an exit shall exit shall comply with Section 1022.1.”

And

IBC 707.5 “Continuity: Fire barriers shall extend from the top of the floor/ceiling assembly below to the underside of the floor or roof sheathing, slab or deck above and shall be securely attached thereto.”

Based on these sections I concluded that for this particular building taking the exit enclosure walls from foundation to roof deck was the most straightforward approach and that neither the floor or the roof needed to be rated.

Originally posted 2010-12-06 00:27:00.

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.