Empirical design & permits...

What is Empirical Design
Empirical building design refers to the tried and proven methods of building with concrete, concrete blocks, and bricks for home construction. Most building codes recognize these decades old building methods as accepted in lieu of specific design engineering. The only requirement is that your project meet minimum design criteria as specified by the code. The book has an entire Chapter devoted to this topic.

This is very good news if you want to design in dry-stacked block construction. As long as your building complies with these minimal requirements, then expensive engineering studies may not be required for building permit approval.

Understanding the industry terminology is a must to expedite code research. I will point out a few of these terms in this section. When searching for these code items, look in the masonry chapters of your code for concrete block reinforcement requirements. Below is an example of one of the many home construction block data tables that can be found in code books. I have added explanation comments at the bottom of the table.

Some of the terms you will be looking for are continuous bond beam span openings, bond beams combined with lintels, vertical wall reinforcement, shear walls, and roof framing connection to bond-beam or bolted top plate.

You will have to find out what the minimal requirements are in your region, but the Florida requirements for 100-mph winds are discussed below as a representative example. Even if you are in Florida, you must still contact your permit office to see what building code is in current use, since the code changes from time to time.

Example Empirical Requirements
Examples of empirical design requirements for dry-stacked CMU, and condensed into lay man terms are listed below. These requirements are representative only and must be confirmed by your local permit office:

One and two family home construction in areas with a basic wind speed of 100-mph or less, shall comply with  the following:

   a. Exterior walls shall be not less than 8" thick for a multi-floor structure, nor less than 6" thick for a
       single floor structure.

   b. A reinforced bond-beam shall be placed around the perimeter at the top and bottom of each multi-
       floor wall with at least one #5 bar. A number 5 rebar refers to a rebar diameter of 5/8-inch. A number
       4 rebar refers to a diameter of 4/8-inch, etc. For the first floor of a dry-stacked structure, the
      (foundation/monolithic slab) attachment meets the bottom wall reinforcement requirement.

   c. Wall area cannot exceed 240-sq. ft. without approved vertical and horizontal support. If your walls
       are 8-feet high, then the maximum wall length without a corner or outcrop is 30-feet. If your wall is 9
       feet high, then the maximum wall section length is about 26-feet. If your wall height is 10-feet, then
       the maximum wall section length is 24-feet.

   d. #5 rebar reinforced wall cell grouted with concrete at each corner.

General Block Construction Requirements
The above list is the minimums to be considered for Empirical design rules. There are additional requirements specified under concrete block construction aspects of the code which consists of but are not limited to:

    a. #5 rebar reinforced grouted wall cell on each side of all doors and windows.

    b. Two #5 rebar in the bond-beam (to meet combined lintel/bond-beam requirements).

    c. Two #5 rebar in all foundation footers

    d. Header rebar requirements are specified in header tables within the code.

Once again, check your local code for exact requirements. For example, you may not need 2 each #5 rebars in the entire bond-beam, but I did it anyway for added strength. My window and door headers were much taller than required (about 24") but that solved many forming issues and window/door framing issues by making the headers higher than required. The code is only the minimums. You can build beyond the code requirements when you feel the need to do so.

There are also general rules relating to a ratio called the Maximum Span to Width Ratio of Floor and Roof Diaphragms. This simply means the length to width ratio of the floor plan and roof plan. For a wood stick structure this ratio is limited to 2:1, but a block structure can be 5:1. This means that if your floor plan is 40-feet deep, then it could be up to 200-feet wide (5:1 ratio). Of course, you still have the 240-sq. ft. rule to contend with, so a wall this long would need outcroppings or lateral reinforcement to break it into smaller sections for stronger home construction.

Lateral Wall Reinforcement
Typical lateral wall reinforcement refers to shear walls or some other engineered reinforcement method. Shear walls are parallel to the lateral forces, and work just like an outcropping. They brace the wall just like a 90-degree corner braces the wall. In other chapters I mention an inside load bearing wall. This could also be a shear wall, and could be used to exceed the 240-sq. ft. rule.

As you can see, complying with Empirical design rules is relatively easy with most home designs. Just keep these issues in mind as you plan your home design. This pretty much sums up your requirements to build under the Empirical design rules. As stated earlier, check with your permit office to confirm their current requirements.

Permit Process
First of all, differing regions of the USA use one of three different building code standards. Here in Florida we use the SBCCI standard. Your region could use one of the other two standards. The examples described here will reflect the SBCCI standard. When you first visit the permit office, the office will provide you with a permit application package, which contains forms for the application of all the required permits for your home construction.

Meeting with the Inspector
When you submit your building permit application, they expect certain plans to be included as specified in the permit application package they provided to you. This is where the rub comes. You can take a shot in the dark and just submit your application, or you can arrange a meeting with the inspector to discuss your project plans. At this meeting is when you want to ask semi-intelligent questions about your proposed plans and how they will be accepted. For example, you might briefly describe your intention to use the dry-stacked block construction method. Because dry-stacking is not yet popular, your building permit office may not be familiar with the process. The will certainly know about it because it is in the building code, but they may have no direct experience with it. Fortunately the code treats building with dry-stacked blocks about the same as building with mortared blocks.

If you take with you the "ASTM C-946-91 (change 91 to current version) Standard Practice for Construction of Dry-Stacked, Surface-Bonded Walls" which can be purchased on the Internet, by searching for the title name; you will impress the inspector and establish a better relationship with that office. It also wouldn't hurt to include the Quikrete product data sheet for QuikWall, or any other surface-bonding product you intend to use. These can also be downloaded from the Internet or mailed from the manufacturer. Once again, you will demonstrate to the inspector that you intend to do a competent job, and you will also provide facts, which should help dismiss any early inspector doubts about the process. After all, the inspector is an engineering type, and specifications are what appeal to him/her.

Don't try to cover every detail at this first meeting. It would be helpful to mention that you are seeking reference standards which describe concrete block construction rebar requirements for wall cells, door and window poured headers, and bond-beams.

That's it, bail out of the meeting with these small tasks accomplished. Now you must review the appropriate standards and the application package you received, and then determine any questions you may have about your proposed plans and the code. I'm not suggesting that you have to learn the building code in detail. I am just suggesting that you read through the building code chapters, which apply to your home construction details.

Your next meetings will be informal and hopefully conducted during the morning questions availability time. Most offices make the inspectors available for building permit questions during the first hour of office operations. This gives all builders a time when they can call or visit an inspector for technical questions about their project. For the remainder of the day; the inspectors will be out of the office, unavailable, and conducting inspections. Once again, only ask a few questions during each call. Space your calls a couple of days apart so you don't appear to be a burden to the inspector. Try to limit your questions to topics you can't find in the building code, or to topics you have found, but you still require further clarification. The inspectors will be much more helpful when they realize that you are reading the code.

Owner-Builder Electrical & Plumbing
In many regions, the owner-builder can also perform all the Electrical and Plumbing work without a license. Of course your work must pass code inspections, but it can certainly save you a ton of money by doing it yourself. Many library books are available on these code requirements, which aren't all that complicated.

Progress Inspections
The building permit office will provide a list of what inspections are required as the project progresses. Make sure you understand what each inspection means. Sometimes the inspection name wording does not relate to conventional naming terms. There is also the problem where most inspection lists are developed for stick built homes. Concrete block construction will have some differences. When you are given the list of inspection requirements, make sure that you clarify the differences for concrete block home construction.

Inspections are typically scheduled when you call an answering machine and request a particular inspection. In my region, if you call before 8AM, Monday through Friday, then the inspection will be conducted on that same day. I usually call the evening before to avoid busy signals. While working on a specific task, when in doubt always make that phone call to the inspector for clarification. It is much better than doing it wrong, failing an inspection, and then having to do it right. I have never failed an inspection to date, but I do my research and ask questions when in doubt.

Abandonment Rules
Last but not least, find out what the timetable is for home construction permit abandonment in your region. Do not ask the inspector (don't wake a sleeping dog…or make the inspector suspicious of your determination), but find the answer in the building code, or County/State law books. Go to your library and start there. Florida has this topic in the State Building Code which is available on the Internet This is important if you are an owner-builder.

The State of Florida considers a building permit abandoned if six months passes without
any approved inspections. Your region may vary. I don't know how lenient building permit offices are with this requirement, but abandonment should not be taken lightly. The consequences are usually extreme. Make sure you understand this aspect of the building permit process. I always keep something I could easily get inspected on the back burner for emergency abandonment prevention.

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