Unusual Attic/Rafter Construction?

[kweiss]

Found this sheetrock sheathing in the attic of a very nice high end home today that is one year old. The rafters on one side had been sheathed in sheetrock about four feet up. This was s single family home with a zero lot line on the side with the sheathing. It looked alot like what you see in a duplex or something. Not wure why it was there and have not seen it in other similar homes in the area.

Any ideas?

[Emmanuel J. Scanlan]

Kevin,

Found this sheetrock sheathing in the attic of a very nice high end home today that is one year old. The rafters on one side had been sheathed in sheetrock about four feet up. This was s single family home with a zero lot line on the side with the sheathing. It looked alot like what you see in a duplex or something. Not wure why it was there and have not seen it in other similar homes in the area.

Any ideas?

Sheetrock is an acceptable 1 Hr fire resistance rated material. Given your description of where it was, and the picture I wonder if it is an attempt at providing a fire rated protection from the home next door? The picture looks like they may have blocked off any ridge vents by placing the rock and what appears to be attempted fire blocks/draft stops at the top of the rock? Were there any blocks at the bottom between the joists? Hard to tell from the picture.

There is a lot of debate going on about zero lot line homes and fire spread. I have not seen this technique though. Were there soffit vents on that side of the home? If no soffit vents could you identify the soffit material?

There are materials available for soffits that are fire resistance rated and even soffit vents that are fire resistance rated. Kind of a moot point on a zero lot line depending on the remaining materials used for the construction. A hot, fast moving fire contacting any other flammable material can negate other individually fire restance rated components. That is one of the reasons for the debate.

[Kenton H. Shepard, CMI]

Squirrel barrier.

[kweiss]

My thought was fire barrier as well. The thing is that the home on the other side is just as close. These are the type where they actually have a little yard. The house on the side witht he barrier yard goes right up to the wall opf the house I was inspecting. On the other side the houe is was inspecting's yard goes up to the next house, about 15' of yard. Yes it does block the soffit vents and the soffit was the kind with the little holes throughout.

Doubt it was a squirrel barrier=) no trees in this new neighborhood.

[ccarrington]

Is that a flexible dryer vent running over the insulations/joists? If it is, you may want to be sure it’s not too long over its max distance. It’s impossible to tell in this photo. I generally recommend hard plumbed dryer piping in the attic, because it greatly reduces lint build up closer to the tail end of the pipe. As air speed decreases slightly the lint often can build in that area. Just a thought…

[Emmanuel J. Scanlan]

Kevin,

My thought was fire barrier as well. The thing is that the home on the other side is just as close. These are the type where they actually have a little yard. The house on the side witht he barrier yard goes right up to the wall opf the house I was inspecting. On the other side the houe is was inspecting's yard goes up to the next house, about 15' of yard. Yes it does block the soffit vents and the soffit was the kind with the little holes throughout.

Given that description I would say it is an attempt at a fire barrier. I did notice in the picture the missing insulation, as compared to the remainder of the joist spaces. Were there any blocks at the bottom of that rock where those openings were? Or did they clear the insulation (I suspect) to allow ventilation from the soffit vents at that point? If no and the second yes then it was just a "Feel Good" measure by the builder as they negated the purpose of the rock and draftstops/fireblocks.

If you approach any builders about this technique I would be interested in what they say is the reference for this technique.

[kweiss]

The duct was a bathroom/laundry room vent vented to the soffit (a common practice around here.) The missing insulation was over the garage.

I did not call anything out as a concern with this. I was just curious as to why it was there. It was a very well constructed high end house with very few problems. My guess was a fire barrier because the neighboring yard touches the house and the possibility of some sort of fire in their yard may exist. I have been in many other houses with a similar layout that did not have this and having not been in any others in the neighborhood, I cannot comment on those.

If I get a chance I may call the builder and inquire about it.

[Kenton H. Shepard, CMI]

That block line alsmost has to mean that it's some kind of draft stop. I can't imagine why it would be required unless it were a situation like 2x4 top plate on 2x6 studs which would provide a fire avenue requiring a draft stop.
Were soffits vents installed?

The zero lot line might be involved but I've never heard of a firestop in the lower four feet of roof. Local bldg dept. might know. I sure don't.