Zero Lot Line

[jackpara]

Dear Sirs;

During a recent conversation with permit office, I have noticed that I am getting conflicting information with each conversation. At first I was told that because my home is being build on a zero lot line the wall on that lot line must be fire rated. If that's the case, I was also told that wall could not have any windows. On that advice and direction I moved the entire house plan around and removed the windows and got the permit based off of that information. I just looked on the website to get information about the veneer inspection and it says "Exterior gypsum sheathing as required for "Zero Lot Line" fire-rated wall assemblies must be installed prior to this inspection". This I don't understand. Does this mean that these walls are automatically fire rated or not? If my plan was approved and the zero lot line wall was not required to be fire rated prior to approval then does this have to be a fire rated wall. Why can I not have windows on that wall? My assumption may be correct because I was also advised later that fire rated walls were dependent on distance between homes. The distance between my home and the neighbor's home is 30 feet. If this is true, again, can I install windows on that zero lot line wall? I have changed these plans to accommodate these regulations and now I see I have been given conflicting information that have compromised the time, value, and physical attributes of my home. Now, all I want is to know the actual policy. The plans for the house were purchased on the internet. Has anyone purchased plans this way and when taken to the permit department had to have changes made to accommodate the permit. I would assume the construction code would be set within those plans or is the permit dep supposed to look at the plans and tell me if I need to makes changes, or accommodate a fire wall? The house is build and waiting for inspection, that why this is coming up. Does anyone know the code or where I can get more information?

Jack

[Bob Morrison]

That is correct information. Assuming your jurisdiction allows "zero lot line" construction for a single family residence (most don't), then IBC2003 requires walls of 1-hour fire resistive construction for an "R" occupancy. Openings are not permitted within 5 feet.

There is no way an "off the internet" set of plans will correctly show this type of information. Most of the time they can't even get the basic structural stuff right, let alone a complex firewall situation.

[Wayne Whitney]

Operable windows presumably are openings, but how about a fixed window? These are available with fire ratings, I believe. I've been wondering about this a bit, as I need to rebuild my existing garage which is right on one of my lot lines.

Cheers, Wayne

[Bob Morrison]

Table 704.8 of IBC2003 indicates that openings are not permitted on any walls 3 feet or closer to the property line. That means no windows and no doors. The exception is if the wall is on an alley or street.

[Wayne Whitney]

So does this prohibition apply only to walls parallel to the lot line, or does it also apply to the portion of a perpendicular wall which is within 3 feet of the lot line? The definition of "fire separation distance" seems to only conceive of walls parallel to a lot line, alley, etc.

Cheers, Wayne

[Bob Morrison]

My interpretation of IBC2003 is that for R-3 & U occupancies (single family residence & Accessory bldgs), ALL exterior walls within 3 feet must be of 1-hour construction and that no openings are permitted in that 3 feet.

From 3 feet to 5 feet you must use protected openings. Beyond 5 feet no protection is required. Refer to IBC2003 Table 704.8 and footnote "f"

[Wayne Whitney]

Thanks Bob for your interpretation; I'll obviously have to check with my local building department to see if they view the requirement the same way. Next year I'll be rebuilding my 10' x 20' garage (on my 41' x 135' urban lot), which is currently right on the side lot line. Your interpretation implies that the garage door can't be any closer than 3' from lot line, so my garage would have to get wider or move away from the lot line.

Cheers, Wayne

[PPS]

Bob, the 2003 IRC reads a little differently, no openings at all permitted on any wall with less than 3' separation (except for foundation vents), but they are permitted on the perpendicular walls (even within the 3' separation distance.) IRC Section 302.1.

As Section 101.2 of the IBC hands authority of detached 1&2 Family dwellings (and town houses) over to the IRC, that would probably by the governing factor in most jurisdictions.

Dennis

[Bob Morrison]

Dennis:

I agree. I don't get into IRC all that much. By the time structures get to me (including houses) they no longer fall under IRC. I just posted the following on alt.architecture

Refer to IRC2003 Section R302.1 which states:

"Exterior walls with a fire separation distance of less than 3 feet shall have not less than one hour resistive rating with exposure from both sides."

R302.2 states:

Openings shall not be permitted in an exterior wall of a dwelling or accessory building with a fire separation distance of less than 3 feet."

Exception 1 allows openings in walls perpendicular to the line used to determine fire separation distance. This means you could put a window right in the corner. However, it will need to be a protected opening per IRC R317.3

[Wayne Whitney]

Can a garage door be made a protected opening?

Thanks, Wayne

[Roger Shoaf]

Having 3 feet on each side of the garage door would not be a bad thing would it? That would give you room for bikes mowers and all of the stuff that accumulates in garages other than cars.

[DanG]

Be very cautious. Many times you cannot tear down the existing and replace because the current codes cannot be met.

I have been involved with several projects that protected and maintained an existing wall, tore down the rest of the structure, and rebuilt. This can be considered a remodel of an existing structure. ______________________________ Keep the whole world singing . . . . DanG (remove the sevens) [e-mail]

[Wayne Whitney]

Sure, all other things being equal, a bigger garage would be nice, but all other things aren't equal. Space is tight, as this is a 41' wide urban lot, and the local zoning regulates the total lot coverage. So it's a matter of preferring to allocate the square footage elsewhere.

Cheers, Wayne

[Wayne Whitney]

That's right. I've already determined that the existing garage is conforming with respect to zoning. So right now I'm trying to figure out if the existing building design meets current building codes. If it does, a complete teardown will be the easiest option.

Cheers, Wayne

[RicodJour]

Make sure you take into account shear wall requirements as well. A garage door the full width fo the garage won't allow that wall to handle the design shear loads.

In my area, within a mile of the water, the increased wind design load pretty much excludes all existing garages from meeting the current code.

R

[Wayne Whitney]

Good point. There are steel prefab shear walls that fit in 12" of width, so I was thinking of a 10' wide garage with a 8' wide garage door, and 1' of shear wall on either side. Or perhaps a 10' 8" wide garage with a 8' door, which allows 10' clear width inside and the use of 16" wooden prefab shear walls. I also understand that it is possible to design a garage as an open box, where the shear load on the open end is taken up by the perpendicular walls via torsion, but that would certainly require an engineer.

Cheers, Wayne

[Bob Morrison]

There is an exception in IBC for 3-sided buildings when the dimensions are less than 25 feet square. Under that exception you must check diaphragm deflections. Refer to IBC section 2305.2.5 Rigid Diaphragms for detailed requirements as there are are number of "sub" rules and exceptions to the exceptions.

[Bob Morrison]

Wayne:

I suggest that you check with a garage door supplier. I believe it is possible, but am not certain.

[Wayne Whitney]

Bob,

Thanks for all the background information. I will first be checking with the AHJ to see what their requirements are. The background helps me orient myself when discussing things with them and helps me have some idea what issues may come up. I believe the California Building Code is still based on the 1997 UBC, so the requirements may be a bit different than the 2003 IBC. Hopefully I won't have to make a garage door within 3' of the property line a protected opening.

Thanks again, Wayne

[Bob Morrison]

Wayne:

California will soon be switching to the "I-codes", so this will no longer be an issue. I believe they will be skipping IBC2003 and going right to IBC2006.

BTW, the "protected opening" language for openings less than 3 feet from the property line on walls perpendicular to the lot line is also in UBC. Refer to UBC Table 5A.