How to Space Sprinklers Under Attic Hip?

10/3/2022

Looking for some guidance on sprinkler layout on eaves and hips.

When laying out an attic, if you design with sprinklers directly under the hips, and want to stay below the 8' spacing against the slope, how does the layout work?

One direction of the roof would be 4' x 7'-6" max, but the other direction of the roof would be reversed, creating a non-linear coverage area.

All of it seems strange to begin with and wondering if I'm overthinking this.

We typically don't design with sprinklers directly under the hips, but I'm wondering if we are over designing with too many sprinklers, etc.

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5 Comments

Jesse

10/3/2022 08:18:24 am

Attic layout can be funny. If you are using the Tyco product the data sheet has some excellent examples.

Eric R

10/3/2022 08:49:12 am

My simple answer is to just use a special application sprinkler! I worked in more attic trusses than I count when I was in the field, and hip roofs were always a challenge. Trying to follow the prescriptive requirements in NFPA 13 can be very difficult when designing in a 3D space like that, and the challenge is compounded when the design hits the field and excess framing elements make it almost impossible to follow the NFPA arrangement rules.

With all the major manufacturers now having listed attic heads on the market using standard spray uprights is just punishing yourself unnecessarily.

Victaulic and Reliable in particular both have excellent arrangement guides for hip roof areas that will let you feel more confident that your layout will work as expected. Also, the fact that none of the specially listed designs utilize heads directly under the hip line (barring TYCO's special HIP head) should probably hint that it's not the best way to protect those areas.

Alex

10/3/2022 09:00:30 am

Hi,

I would highly doubt that attic design would be anyone's favorite area... I've used the Tyco spec sheets to help in the past.

Link: https://www.tyco-fire.com/products-and-solutions/sprinklers-nozzles-and-accessories/special-application/attic_fis/attic-sprinklers#technicalspec

Thanks,
Alex

Steven

10/3/2022 09:01:13 am

I agree with Eric, I almost always prefer the special application attic sprinklers from a design standpoint. However, they are substantially more expensive and sometimes they won't save you enough sprinklers to justify the cost. When you do have to use standard spray sprinklers, you are certainly right -- sprinkler head layouts at the hips can end up looking a bit strange. I doubt you are overthinking it -- attic layouts can be quite challenging, especially if you are also installing it as a dry system.

I can share how I like to handle the sprinklers near the hips, but there are of course many ways to do it (and I'm not saying my method is the best, it just works for me). I start by laying heads out along the ridge, which is normally easy enough. Once we get to the hip, I treat it almost as if it is a wall -- I lay out heads down each part of the roof slopes, independent of each other. In other words, I space heads along the east-sloping roof with spacing up to 15'-0 x 8'-0, usually staggering the heads from the row of heads above. As I approach the hip (which I am temporarily treating as a wall), I make sure I have a sprinkler within 4'-0 of it (half of 8'-0). I do the same thing on the north-sloping roof, and the west-sloping roof. Then, I go back and adjust the heads with respect to the hips -- sometimes they will be too close to each other, so I have to shift them one way or another (usually shift in increments of 2'-0 or whatever the truss spacing is). Often it'll take a few iterations of shifting heads, or entire lines, before everything looks okay. As for the corners of the roof, sometimes it might require an extra head to pick up that coverage.

Anyways this is certainly not the only method, nor is it necessarily the best. I'd like to hear if other folks have suggestions or comments.

Sean K link

10/4/2022 09:02:59 am

Check out Victaulic’s line of attic sprinklers, which even come in a ‘Low Flow’ scheme which reduces water by roughly 70% resulting in system demand ranging from 130-180 gpm.
Victaulic even has a team of experts which are available to support with layout needs and work alongside your design team until it’s done per the submittal specs considering these are ‘specific application’ sprinkler heads.

https://www.victaulic.com/assets/uploads/literature/46.03.pdf

https://www.victaulic.com/assets/uploads/literature/46.02.pdf

https://www.victaulic.com/assets/uploads/literature/46.02.pdf

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How to Space Sprinklers Under Attic Hip?

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