It’s been a while since my last post as I had to take some time off building to put my house up for sale and finish moving all of my belongings into a shipping container on the lot. I also discovered that when you want to get a building permit appointment, you should apply about a month ahead! They call it an “intake appointment” (still don’t know why) and once again the county website was very helpful in letting me know just what I needed to bring (copy of deed, septic design, proof of water availability, 2 copies of plans, etc) The website had links to download several documents to bring, but one of the links didn’t work. I eventually decided it was probably not important.
Three weeks later the big day finally came! I went through the checklist provided on the website one more time and double checked my plans (I ended up finding a few mistakes and had to reprint two copies of a few pages!) I was nervous and didn’t really know what to expect but it was actually pretty simple. The plans examiner met me at the counter and unrolled my plans. He looked at them for about 5 minutes and then told me that I was missing one thing and needed engineering. I was frustrated but not too surprised (I’m a beginning builder after all!) The missing item turned out to be what I needed from the link that didn’t work that I had decided wasn’t important. He admitted that they knew the link didn’t work and showed me where to find the documents. He told me I needed engineering because my braced wall lines exceeded the maximum of 25′ and that my deck could only extend 6′ from the exterior wall of the house (I had extended it 12′). I was completely caught off guard and I gave a half hearted attempt to argue that my plans followed all of the county’s building codes but I also started to second guess myself. Perhaps I had made a mistake? I had drawn up the plans for the wall bracing months ago and didn’t quite remember the details. He made an appointment for me for the following week and I left, disappointed but not deterred. As soon as I drove home I grabbed my copy of the International Residential Building Code (IRC) and double checked. I was right! The codes clearly dictated that my exception to the 25′ max was admissible. Furthermore, I couldn’t find anything limiting decks to 6′ in the pertinent section (R507)
I wrote the plans examiner an email clearly stating the codes that allowed me to exceed the braced wall line spacing (for those who want to get technical, make sure you read my post on wall bracing and then read at the bottom of the post) and also asked him politely to refer me to the code that limited the deck to 6′. Unfortunately, it was Friday, so I had to wait through the weekend to hear back. I reluctantly called an engineer as a backup plan and he told me he would happily provide engineering for me… for just a thousand dollars… When Monday finally came, the plans examiner emailed back and informed me that the exception I was using on the bracing could only be used on one wall, and I was using it on two. For the deck, he referred me to code 301.2.2.2.5. Once again frustrated and thinking I had made a mistake, I painstakingly read through the code again. There was nothing anywhere limiting the bracing to one wall! For the deck, the code he referred me to discussed irregular shaped houses, not decks! My house was a perfect rectangle – one of the most regular shapes there could ever be! I wrote him one more time asking him politely to provide the code that limited the exception to one wall and an hour later he called back with the incredible news! He admitted he was wrong! Sweet, sweet vindication was mine!! For the deck, he wrote that the county had decided to apply 301.2.2.2.5 to decks as well. This was frustrating, but only a minor setback. I would be able to build the house without expensive engineering and I could always add to the deck later. The engineering for just a deck would be half the price. I would have to reprint my plans (at the price of $30) but if all goes well I should have my permit in another 4 days! I already have a backhoe reserved for Saturday so I can start digging the foundation!
Read this next section at your own risk! We are about to get very technical and very boring! So for those who are interested in how I taught the plans examiner something new, I will let you know. In review, braced wall lines are imaginary lines that are designed into the house to protect against shear forces (wind, earthquakes, etc) The section of the IRC that discusses wall bracing (602.10-602.12) is one of the most complex of the entire code and takes up at least 15 pages. One of the first issues covered is the spacing of these imaginary lines. As you can see in the table above, in my seismic zone (D1), the lines can be spaced no more than 25′ from each other. However, if you read the bottom right box, there is an exception that allows the spacing to extend up to 35′. As you learned from my post on wall bracing, these imaginary braced wall lines must contain a certain amount of braced wall panels that run parallel to the imaginary braced wall line with an offset of no more than 4′. The exception I am using allows the spacing to exceed 25′ only if the amount of braced wall panels is increased.
For me, this was no problem. The main obstacles to planning for a braced wall panel are large openings like windows, and garage doors. When I designed the house, I decided to go easy on the windows so I could afford to buy really good ones. Windows are quite inefficient when it comes to sustainability. They let the hot sun in on hot days and let the heat dissipate through them out of the house on cold days. These effects can be mitigated by buying windows with low U-values, low SHGC (solar heat gain coefficient), and insulated frames, but at a significant cost. Saving Sustainably means using fewer windows, but spending the money to get really good ones and strategically locating them.
Getting back to the point, I had no problem with adding more braced wall panels to my imaginary lines. Let’s take a look at the first table that was referenced in my exception to the 25′ maximum braced wall line spacing.
The table is quite long, but we will just focus on the section that applies (seismic zone D1). If you look on the far right side of the table you will see the CS-WSP method. This stands for Continuous Sheathing Wood Structural Panels. It means that we will nail plywood (or OSB) to the exterior of the framing of the house, and wherever we locate a braced wall panel, this “sheathing” will extend all the way from the bottom of the wall to the top of the wall (with no openings for windows, doors, etc). My exterior walls are 24′ and 32′ long and at the bottom of the table there is a footnote that says “linear interpolation shall be permitted”. Therefore, we can find the amount of bracing necessary with some basic math. The results are….
Main Floor 24′ Walls – roughly 9’7″ of bracing
Main Floor 32′ Walls – roughly 12’4″ of bracing
2nd Floor 24′ Walls – roughly 4’4″ of bracing
2nd Floor 32′ Walls – roughly 5’6″ of bracing
Now, let’s take a look at the second table that was referenced.
Looking at item 3, we can see that the braced wall line spacing can be increased to between 30 and 35 feet if the amount of bracing in each wall is increased by a factor of 1.4.
I recalculated the bracing, rounded up to the nearest 2′ increment, and came up with the results that I noted on my plans.
It might be hard to make out but if you look closely you can see the triangles along the exterior walls that denote the braced wall panels, and if you add them up you can verify that I have satisfied the requirements of the exception to the 25′ max.