# Lower walls of TOP/BOTTOM Duplex



## righter101 (Apr 3, 2014)

Hello everyone.

Duplex, one unit above, one below.  Non-sprinkled (per Wa. State amendment).

1 hour floor ceiling required.

Also required is the support of the 1 hour F/C assembly.

In this case, that is the lower walls.

Section R302.4.2 exceptions addresses the electrical boxes, so that is clear but what about windows and doors on the lower floor?


----------



## tmurray (Apr 3, 2014)

We wrap the openings.


----------



## fatboy (Apr 3, 2014)

In the duplex you are describing, it sounds like as long as you maintain the 1-HR separation horizontally, anything within the individual dwelling units is not regulated, interior or exterior walls, except fire separation line requirements of course.


----------



## fatboy (Apr 3, 2014)

"We wrap the openings."

What openings? Building envelope? Wrap how?

Just curious as to the thinking..........


----------



## righter101 (Apr 3, 2014)

fatboy said:
			
		

> In the duplex you are describing, it sounds like as long as you maintain the 1-HR separation horizontally, anything within the individual dwelling units is not regulated, interior or exterior walls, except fire separation line requirements of course.


R302.3.1 Supporting construction. When floor assemblies are required to be fire-resistance rated by Section R302.3, the supporting construction of such

assemblies shall have an equal or greater fire-resistance rating.

This section leads me to believe that the lower level unit walls need to be 1 hour rated as well.  R302.4.2 Membrane penetration address (through the exceptions) electrical boxes.

I am just not clear if doors and windows would need to be rated as well, based on R302.4.1 Through penetrations. Through penetrations of

fire-resistance-rated wall or floor assemblies shall comply with Section R302.4.1.1 or R302.4.1.2.

Our zoning prohibits duplexes in most areas so we don't get them often.


----------



## mtlogcabin (Apr 3, 2014)

Windows and doors are openings are not really a membrane through penetration by a pipe, conduit or similar item.

Most window and door openings are framed with a header across the top and double 2X down the sides which would be a minimum 3 inches of wood. Do you know the burn time on a 3 inch thick piece of pine?

I believe you are over thinking this one.


----------



## righter101 (Apr 3, 2014)

mtlogcabin said:
			
		

> Windows and doors are openings are not really a membrane through penetration by a pipe, conduit or similar item.Most window and door openings are framed with a header across the top and double 2X down the sides which would be a minimum 3 inches of wood. Do you know the burn time on a 3 inch thick piece of pine?
> 
> I believe you are over thinking this one.


Consider them "openings" instead of a "through penetration"?

That works.  Thanks for the input.


----------



## fatboy (Apr 4, 2014)

Yes, I undersand and agree about supporting construction, just don't believe it applies to doors and windows, should have been clearer.


----------



## tmurray (Apr 4, 2014)

fatboy said:
			
		

> "We wrap the openings."What openings? Building envelope? Wrap how?
> 
> Just curious as to the thinking..........


With the fire protection membrane. If you don't wrap these openings the fire can short circuit the fire protection membrane and cause premature failure of the structure.


----------



## Builder Bob (Apr 4, 2014)

The door frames and window framing usually have several studs or a header that is thicker than 1 1/4" which is the char rate for an hour of southern pine. Wrapping these openings tend to be exceesive for the building codes and create problems with securment of the windows and doors since sheetrock is fragible.....i.e. not a hard firm surface. Moisture and time degrade sheetrock.


----------



## righter101 (Apr 4, 2014)

Thank you to everyone for the thoughtful feedback and discussion.


----------

