Cement board for sheathing

[atrizzy]

Hi all,

I'm tasked with designing a CFS stud structure with minor lateral loads without utilizing combustible materials.
Usually I'd screw a plywood floor and wall sheathing onto the framing and be done with it. However, the requirement for non-combustible materials is bringing up the topic of cement board.

Does anyone know of any design guides for use of cement board in lateral resisting systems?
The load are small, so I'm more concerned that there BE a load path rather than how strong it is, but it would be nice to have something to hang my hat on at the end of the day.

Thanks very much.

 

[SJBombero]

Sure Board is the got-to product for non-combustible sheathing. I have never looked into cement board but I would think it would be at least as capable as gypboard. But if you are in a high seismic area, gyp board is not an option.

 

[XR250]

What about Densglass?

 

[GC_Hopi]

You can check out AISI S213-07/S1-09 (2012).

 

[phamENG]

For the floor sheathing you could look into Structo-Crete (a non-combustible floor sheathing with diaphragm testing from USG).

For the walls - densglass should give you enough if the loads are really small. If you find that lacking or you don't like the idea of using gypsum based shear walls (I'm not a big fan if it can be avoided), you can go with flat strap shear walls.

 

[SJBombero]

Per ASCE 7 Table 12.2-1, CFS walls with shear panels of materials other than WSP or steel sheets are not permitted for SDC E & F. In ADC they are limited to structure heights of 35 ft.

 

[atrizzy]

Thanks everyone, Sure-board is the answer I was looking for.

 

[GC_Hopi]

Out of curiosity what is the magnitude of the shear values for that Sure-board? I know OSB with CFS studs it is around 700 lb/ft on the low end.

 

[atrizzy]

GC, see the spec sheet below. Last few pages.

https://floorsheathing.com/wp-content/uploads/2019/03/MW-SB-Floor-Sheathing-Flyer.pdf

 

[driftLimiter]

Pretty impressive levels of shear resistance reported in that link @atrizzy. But it is only indicated as horizontal diaphragms. I wonder if they have any testing on wall arrangements.

 

[atrizzy]

Yes, good point, driftLimiter.
It's sure to be well within what I require so I haven't dug any further, but I'm sure the information is available.

 

[MotorCity]

Have you looked into diagonal metal strapping?

 

[atrizzy]

MotorCity, yes, that's an option but in that case it would still need to be sheathed with something, especially for floor load. Might as well kill 2 birds with one stone.

 

[Aesur]

Sounds like your best solution is concrete over steel deck, maybe 2" of concrete over form deck or something like that since you are needing this for a floor versus shear walls. Shear walls are easily sheathed with steel sheets in lieu of wood per AISI publications.