|
Introduction
As to home fire safety in home building plans, much codified ado is made of fire-blocking wall and floor structure. but not much at all on stairway design and stairway construction.
Comment: This codified ado even sort-of includes home fire safety in regard to stairway structure. See IRC 2003, R311.2.2 “Under stair protection. Enclosed accessible space under stairs shall have walls, under stair surface and any soffits protected on the enclosed side with ½-inch (12.7mm) gypsum board." For fire safety in stairway design and stairway construction, it’s a beginning.
Note, please, that there’s no mention of fire-rated gypsum board and heavier weight material as are referenced elsewhere – and have been for quite a long while – for garage wall and ceiling surfaces abutting habitable space.
Important Digression
And there are the high-value references to smoke alarms in home fire safety building codes nationwide, references albeit at minimum levels of materials and methods, in the author’s opinion.
Comment: Minimums? That’s what this house designer thinks. Following are designer house plan set stipulations that Before The Architect writes into smoke alarm methods and materials to extend home fire safety codified minimums, among them –
- shall run on both permanent 120V and replaceable battery
- shall feature a combination of ionization and photoelectric sensors and
- shall not disconnect by wall switch
- shall connect to a 120V line as first load on a frequently used lighting circuit with overcurrent protection at the panelboard suitable for a double tap
- [for sleeping areas] shall install according to manufacturer’s specifications on either side of any passage between a sleeping area and a path to egress
Home Fire Safety - Stairway Design and Stairway Construction Prologue
So, what about the eminently more airflow-permissive stairwell itself?
In a house aflame, a residential interior stairway can occasion two events:
- the passage of both occupants to safety and firemen for the sake of safety
- the passage of smoke and flame between interior floor levels
It might seem as though interior stairway design and stairway construction, this key locus of interior structure in interior fire conditions – good (human transport) and bad (smoke and fire transport) – is at least largely forsaken by residential building authorities having jurisdiction.
What to do? What to do?
In regard to stairwells, that is stairwell design and stairwell construction, what’s at stake is fire-degraded stairway construction, wood stud walls and wood ceiling joists collapsing within the stairwell, engaging stairway and its contents, including people contents, and thereby precluding occupants' easy physical movement between floor levels.
Home Fire Safety - Interior Stairway Design Fire Safety Guidelines
- A residential, interior stairway, other than a spiral stairway -
- Below the stair stringer
- Shall be sheathed
- from outer stair stringer to outer stair stringer including header cleat
- with not less than 1 layer of 5/8" Type-X gypsum board glued, screwed, and taped
- Shall be mudded not less than 3 coats, paying particular attention to screw pocks which shall be taped, too
- Where walls run below or immediately next to outside stair stringers
- shall be framed at walls with lightweight, or cold-formed, steel
- shall be sheathed on the exterior with 1 layer-5/8" Type-X gypsum board glued, screwed, and taped
- shall be mudded not less than 3 coats, paying particular attention to screw pocks which shall be taped, too
- If continuous Type-X envelope cannot be applied on the vertical below a staircase, then contractor
- shall frame with lightweight, or cold-formed, steel
- shall sheathe
- the interior with 2 layers-5/8" Type-X gypsum board glued, screwed, and taped
- where applicable, the exterior sheathed with 1 layer-5/8" Type-X gypsum board glued, screwed, and taped
- shall be mudded not less than 3 coats, paying particular attention to screw pocks which shall be taped, too
- Where stairwell wall extends above a stair stringer as, for example, a stairwell, or below a stringer as, for example, a mid-landing, contractor
- shall frame the wall in lightweight, or cold-formed, steel
- shall sheathe the interior with 2 layers-5/8" Type-X gypsum board and, where applicable on the exterior of the wall sheathe with 1 layer-5/8" Type-X gypsum board
- shall sheathe the exterior with 1 layer-5/8" Type-X gypsum board glued, screwed, and taped
- shall be mudded not less than 3 coats, paying particular attention to screw pocks which shall be taped, too
- shall be sealed at a protrusion with fire-stopping materials conforming to not less than most current ASTM E84 and E814, which sealing shall not necessarily exclude consideration of tumescent sealant
- Under stair in closet, cabinet, niche, alcove, bookcase, or similar
- a high-voltage electrical device or appliance shall not be sited
- steel frame shall be sheathed continuously, fastened, and mudded at all abuts before other finish clad is applied, that is, the first exterior clad to steel frame below a staircase shall be at least 1 layer-5/8"Type-X gypsum board applied as above
In sum, the steel’s there to break down more slowly when engaged, to wrack and sag but not to cinders and ash; the extra layers of Type-X are there to better hold its form and hold flames from you on your way up or down the steps. |
tweet this!