Thread: Walls
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Old 09-25-2017, 08:49 PM   #3
evileeyore's Avatar
Join Date: Jul 2006
Location: 100 hurricane swamp
Default Re: Walls

What's the exterior wall made of*? And the interior walls?

Personally I'd call each 1/2 of sheetrock (wallboard) 1 DR and 2 HP, most interior wall are 2 layers (1 inch) of sheetrock (two separate layers, one of each side). Better built homes (more noise proofed) will be 4 layers, however this is 2 separate layers of 2 on each side of the wall, so 2 DR 4 HP and then another 2 DR 4 HP.

The walls between different units in an apartment building should also be 4 layers often times with a mesh screen between (chicken wire) which should add a separate 2/0 DR 4/0 HP (the second number is versus pi).

Each layer of sheetrock is 30 minutes fire rated**, so versus fire it has a lot more DR.

* Basic Set recommends 6 DR exterior walls for modern buildings, which if made of empty cinder block almost*** sounds right. If it's properly filled with concrete however (which it should be! And reinforced to boot!) that's 6 inches of concrete... which I would treat as brick for blow through purposes only, so DR 16 HP 16.

** Which with only 1 layer drops to mere minutes at seams. This is also why better built homes use multiple layers on each side of a wall, they overlap the seams better to give a greater heat and fire insulation.

*** I was popping cinder blocks with a .38 as a kid, so... maybe 6 DR is a leetle high for a 'void' cinder block construction house. And it feels weak for a solid 6-7 inches of reinforced concrete and block , which is what I'd call a 'modern middle class home'.
Feel free to steal, borrow, fold, spindle, mutilate any rule, advantage, etc I come up with it.
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