Home Fire Safety – Interior Stairway Design Fire Safety Guidelines

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INTRODUCTION

This article is about custom home designing fire safety in an interior stairway.

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 custom home designer thinks. Following are designer house plan set stipulations that may be written into smoke alarm methods and materials to extend home fire safety codified minimums. Each alarm shall run on both permanent 120V and replaceable battery, shall feature a combination of ionization and photoelectric sensors. None shall disconnect by wall switch. Each 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, an alarm shall be installed 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 and the passage of smoke and flame between interior floor levels.

Comment: 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. It 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. The steel frame shall be sheathed on the exterior with 1 layer-5/8″ Type-X gypsum board glued, screwed, and taped. It 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. It 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. The frame shall be sheathed on the interior with 2 layers-5/8″ Type-X gypsum board and, where applicable, on the exterior of the wall with 1 layer-5/8″ Type-X gypsum board glued, screwed, and taped. Sheathing shall be mudded not less than 3 coats, paying particular attention to screw pocks which shall be taped, too.

Sheathing 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 at under-stair in closet, cabinet, niche, alcove, bookcase, or similar. 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.

A high-voltage electrical outlet, device, or appliance shall not be sited anywhere below a stairway.

In sum, the steel’s there to break down more slowly when engaged, purposely 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.

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