rispgiu Posted March 14, 2018 Share Posted March 14, 2018 I am drafting a few duplexes, I've never done one nor actually built one so I was wondering if the interior walls dividing the two units need to be 6" each, or just build a main wall in the middle of the two units at 10"-12". Any suggestions would be greatly appreciated Link to comment Share on other sites More sharing options...
rispgiu Posted March 14, 2018 Author Share Posted March 14, 2018 Thank you Eric, thats a great idea. Link to comment Share on other sites More sharing options...
RL-inc Posted March 14, 2018 Share Posted March 14, 2018 Depends on if you are designing structurally independent units or just 1 hour fire separation. As Eric said check with local authority but ultimately up to you and the client to decide what you are really building. Will the units be individually owned- or just rented by landlord. 1 story or 2- fire rated asemblies for walls only or full separations to roofs searching. Lots of good info from the APA and United Gypsum board association. 1 Link to comment Share on other sites More sharing options...
lbuttery Posted March 14, 2018 Share Posted March 14, 2018 as stated check with local building dept may require two separate walls with an air gap between them besides fire there are also sound transmission issues Lew 2 Link to comment Share on other sites More sharing options...
DRAWZILLA Posted March 14, 2018 Share Posted March 14, 2018 You can also look up fire rated assembly's and sound rated on the internet, lots to find there 1 Link to comment Share on other sites More sharing options...
Kbird1 Posted March 14, 2018 Share Posted March 14, 2018 Chief calls these Marriage Walls ( a term I am not familiar with? ) but it is basically a Double Wall (Furred Wall Type) , there is a KB Article here : https://www.chiefarchitect.com/support/article/KB-00925/using-marriage-walls.html A Double Wall with 5/8" FIRE Drywall TO THE RIDGE BOARD usually gets you by for Code but Soundproofing as also a big issue , but checking with the Local City ( to the Build ) is important , as many City's also have there Own Fire Code on top of the National Code. M. 1 Link to comment Share on other sites More sharing options...
lbuttery Posted March 14, 2018 Share Posted March 14, 2018 I've heard them called "zero lot line" walls Lew Link to comment Share on other sites More sharing options...
chief58 Posted March 14, 2018 Share Posted March 14, 2018 If your looking for a true fire separattion we spec a product called shaft wall and from a 2 x 4 wall on each side to put any electric or plumbing into this way there is a true firerated wall between and I beleive it is a 2 hour rating, I uploaded one of my details for that wall shaft wall.calibz 2 Link to comment Share on other sites More sharing options...
rispgiu Posted March 14, 2018 Author Share Posted March 14, 2018 Thank you all, this is truly very helpful. Link to comment Share on other sites More sharing options...
para-CAD Posted March 14, 2018 Share Posted March 14, 2018 Every party wall I ever framed was (2) separate walls. Some had fire-rated GWB in the 2" gap space plus sound batting 4x8 sheets. I have a sketch at the point in time in this video 3 Link to comment Share on other sites More sharing options...
NRST8TRKR Posted March 14, 2018 Share Posted March 14, 2018 Thank you Chief 58. Have not had any issue with local Building Depts. with the way I have been showing Firewalls but this is a much better job. Have a great week,Ken. 1 Link to comment Share on other sites More sharing options...
Alaskan_Son Posted March 14, 2018 Share Posted March 14, 2018 We have been involved in the construction of MANY duplexes and here's how we've typically handled that area. I just copied Ray's CAD block and modified it a bit... PARTY WALL EXAMPLE.calibz 1 Link to comment Share on other sites More sharing options...
chief58 Posted March 14, 2018 Share Posted March 14, 2018 Michael the way you show the party wall example what fire rating would you get not using the shaftwall material, inspectors here want a full firewall between party walls for fire a 2 hour fire protection between each unit, I might be wrong the way you have it if a fire breaks the 5/8 type x sheetrock it could get into the other walls and other apartment, I know on the townhouses I always spec the shaftwall Link to comment Share on other sites More sharing options...
Alaskan_Son Posted March 14, 2018 Share Posted March 14, 2018 33 minutes ago, chief58 said: Michael the way you show the party wall example what fire rating would you get not using the shaftwall material, inspectors here want a full firewall between party walls for fire a 2 hour fire protection between each unit, I might be wrong the way you have it if a fire breaks the 5/8 type x sheetrock it could get into the other walls and other apartment, I know on the townhouses I always spec the shaftwall The way we've always done it gets a double layer of 5/8" on both units which should give it a 2 hour fire rating. This double layer continues top to bottom except where solid framing can be included in the fire rating calculation. I don't know off hand what the fire rating of most lumber is, but as I recall its somewhere in the neighborhood of 1/2 hour per nominal inch meaning we might only put one layer of 5/8" over 2x joists in the center, or if joists/trusses are running perpendicular we might use 4x blocking and no GWB at all. If we're using I-joists then they would get the full 2 layers. It all really depends on the job though. 1 Link to comment Share on other sites More sharing options...
chief58 Posted March 14, 2018 Share Posted March 14, 2018 Michael as always thank you for the information 1 Link to comment Share on other sites More sharing options...
Kbird1 Posted March 14, 2018 Share Posted March 14, 2018 3 hours ago, Alaskan_Son said: The way we've always done it gets a double layer of 5/8" on both units which should give it a 2 hour fire rating. This double layer continues top to bottom except where solid framing can be included in the fire rating calculation. I don't know off hand what the fire rating of most lumber is, but as I recall its somewhere in the neighborhood of 1/2 hour per nominal inch meaning we might only put one layer of 5/8" over 2x joists in the center, or if joists/trusses are running perpendicular we might use 4x blocking and no GWB at all. If we're using I-joists then they would get the full 2 layers. It all really depends on the job though. Double 5/8" works great for Sound Transmission too, and is usually Cost effective but a diligent Installer of Rockwell Roxul/Rockwool is needed too... as Air Cavities/Gaps = Sound Transmission. Make sure to have all penetrations like Electrical Outlets/Switches are Air Sealed too. M. 1 Link to comment Share on other sites More sharing options...
Alaskan_Son Posted March 14, 2018 Share Posted March 14, 2018 19 minutes ago, Kbird1 said: ...but a diligent Installer of Rockwell is needed too... I assume you meant Rockwool (mineral wool)? Ya...we don't use the stuff around here. Pretty much always fiberglass for everything. By the way, one other thing that can be pretty easily and affordably added to the assembly to help reduce sound transmittance even further is RC channel (resilient channel). Link to comment Share on other sites More sharing options...
rispgiu Posted March 14, 2018 Author Share Posted March 14, 2018 I am always blown away by the support, encouragement and information received by this community . You guys are the best and in my opinion you make CA worth more than what it costs. Thank you all sooooo much. 2 Link to comment Share on other sites More sharing options...
rispgiu Posted March 14, 2018 Author Share Posted March 14, 2018 5 hours ago, para-CAD said: Every party wall I ever framed was (2) separate walls. Some had fire-rated GWB in the 2" gap space plus sound batting 4x8 sheets. I have a sketch at the point in time in this video Thank you this is great. Link to comment Share on other sites More sharing options...
rispgiu Posted March 14, 2018 Author Share Posted March 14, 2018 3 hours ago, Alaskan_Son said: We have been involved in the construction of MANY duplexes and here's how we've typically handled that area. I just copied Ray's CAD block and modified it a bit... PARTY WALL EXAMPLE.calibz Thank you very much for sharing this. 1 Link to comment Share on other sites More sharing options...
Kbird1 Posted March 15, 2018 Share Posted March 15, 2018 1 hour ago, Alaskan_Son said: I assume you meant Rockwool (mineral wool)? Ya...we don't use the stuff around here. Pretty much always fiberglass for everything. By the way, one other thing that can be pretty easily and affordably added to the assembly to help reduce sound transmittance even further is RC channel (resilient channel). Oooops Yes RockWool , I think SpellCheck must have gotten me there it was Roxul but is going through a rebranding at the moment.... My understanding was that Mineral Wool (Roxul) is better at Sound control and also can have a higher R-Value but I have not looked at any recent innovations in that area ( if there has been any?) so I use it in Sound applications but Fiberglass Batt normally. I actually prefer Blown Cellulose in Ceilings, and it's easy in Remodels for top ups etc. Spray Foam if they can afford it (or needed). In Alaska you may have different methods though.... https://www.rockwool.com/a/b/hello/ Link to comment Share on other sites More sharing options...
RL-inc Posted March 15, 2018 Share Posted March 15, 2018 Might as well jump on board- attached fire wall detail commonly used around here. Valid for rental units or individually held properties such as condo plats and townhomes. TYPICAL BUILDING FIRE SEPARATION DETAIL.dwg 1 Link to comment Share on other sites More sharing options...
rispgiu Posted March 15, 2018 Author Share Posted March 15, 2018 Just to keep everyone updated: I have drafted the first duplex, not finished yet but enough for the developer to present a concept. It was actually fairly simple after all of the great suggestions you guys have provided. By using the "marriage wall" that Mick suggested that simplified a whole lot of things (foundation, roof and framing) Thank you all so very much. 1 Link to comment Share on other sites More sharing options...
dscaddoo Posted March 16, 2018 Share Posted March 16, 2018 In my neck of the woods its typically done the same way @chief58 has described. I am also from PA. USG calls it an area separation wall assembly and has some pretty good literature available on their website. I'll include the link. They are designed such that one of the units can completely collapse in a fire, and the firewall should remain relatively intact so as to minimize damage to adjoining units. USG has an article describing a case just like that. I used it on an addition i built on a twin home a few years back, and it is a simple and effective way to construct a separation. Easily installed by carpenters as the building is being framed. I'll attach some photos of it during construction. Another typical detail on townhouses around here is to use fire treated plywood sheathing on the exterior walls and roof surface for a minimum of 4' on either side of the firewall. Section R-302 of the IRC goes over everything in great detail. One homebuilder around here uses an 8" concrete bock wall as the firewall between units. Key is for whatever system you choose is that its continuous from the foundation to the underside of the roof sheathing, and from exterior sheathing to exterior sheathing. https://www.usg.com/content/usgcom/en/products-solutions/products/wallboard/wall-systems/usg-area-separation-wall-system.html 2 Link to comment Share on other sites More sharing options...
RL-inc Posted March 18, 2018 Share Posted March 18, 2018 Absolutely.....very standard assembly. And nice post with the example pics... 1 Link to comment Share on other sites More sharing options...
Recommended Posts
Please sign in to comment
You will be able to leave a comment after signing in
Sign In Now