This e-article is about shear wall design and construction details
Before The Architect (BTA) doesn't design shear walls; engineers design shear walls
The hitch:engineers don't build shear walls; contractors build shear walls
What follows about shear walls speaks to both engineers and contractors - common senseand consummate construction standards
IMPERATIVES IN SHEAR WALL DESIGN AND CONSTRUCTION
Shear wall sheathing shall be
Not less than 5/8 linear inch, Structural 1 plywood
Applied in a vertical orientation only
Lapped over sill and top plates, sharing double top plates in multilevel-overgrade designs
Shear wall shall be fastened
At joints to other sheathing
With galvanized wood screws, not nails
Driven only perpendicular (i.e., only straight) to a shear wall plane
Not overdriven
Only after approval of fastener materials and methods by engineer, inspector, and contractor
For inspection before wrapping the house
On not greater than 4 linear inch centers
At not less than ½ linear inch in from sheathing perimeters
Without application of construction adhesive at joints with members
Shearwall fastening shall be
Of eave blocking to roof frame and top plate, the latter with not less than 3-10d common galvanized nails per block
Which eave blocking shall be full depth and
Which eave blocking may be bored to let passive airflow from soffit to ridge or gable vent
Which eave blocking shall baffleto block wind from insulation while still assuring not less than 2 linear inch air gap to roof deck bottom of face
Of an anchor bolt
Not to be double-dutied as a hold-down bolt
Not less than 5/8 linear inch in diameter
Of sole plate or mudsill
Not less than 12 linear inches on center for bottom, of sole plate, or mudsill
Spaced at half field spacing when applied to walls shear wall- sheathed on both faces
Fastened each with a square washer 3 linear inches on a side and not less than 3/16 linear inch thickness
Shall penetrate its sill
Through a hole not larger than 1/16 linear inch larger than the bolt diameter
Failing which
The hole shall be fully filled with a nonshrink grout or epoxy or epoxy-grout by Laticrete International, Inc. et al.
Shall be, with its washer and nut
Set flush to sill top of face and not recessed
Tightened at the last possible moment finger tight plus a half-turn
Shall be as an in-line grouping reinforced with a single, continuous deformed #5 rebar set a J-bolt curve
Of a tie-down shall be
At each end of each wall section
Applied to a post interior if possible
Fastened to a post with self-tapping screws
Concentric in application to a post
Of a shear wall panel
Shall be applied on the interior directly to structure and thereafter finished with gypsum wallboard – screwed in shear wall plywood fastening patterns
Shall, as a group and without regard as to whether its site is interior or exterior, extend at gable end fully from sill to top plates continuously and without interruption or gaps (except, of course, for stand 1/8 linear inch spacing between ply sheets)
Shall be addressed as a load to be born by subordinate structure
Shall be at each and every one of its intra-bay joints blocked fully and firmly with x4 whole or built-up lumber
Load paths shall be of materials continuously solid and sufficient throughout to prevent crushing, notably (and preferably) up-sizing posts, and blocking below post- and stud-loaded sills, i.e., crush blocks
Of metal connectors, straps, hangers, etc. fastened only with a full complement of nails or screws specified by the manufacturer or engineer of record
Of connections of members shall be to full members without exception
Shear wall shall be braced
With not less than full-depth, solid blocking
With not less than x4 material, whole or built-up
On center to blocking at joints and
On not greater than 6 linear feet centers
Plus inside of and tight to top and bottom plates
Not with flat straps for compression
Possibly with block-U, structural steel channel
Possibly – with space to be taken up – with members sistered at 90-degrees to studs' narrow faces
Shear wall shall be framed
With not less than x4 nominal width, i.e., narrow face, at all joints to sheets and otherwise at all perimeters of sheets
With not less than x6 linear inch nominal depth members overall
May be of engineered lumber
With metal hangers and not jack studs to affix a beam, including a header
Where jack studs are changed-out for king studs
With lumber
Identified by the grade mark of a lumber grading or inspection bureau or agency approved by the American LumberStandards Committee(a/k/a ALSC)
Group 2 or 3
Not less than #2 Grade
In decreasing order of preference of specie
Douglas Hemlock Fir-Larch
Southern Yellow Pine
Spruce-Pine-Fir
For engineered applications only and then
Only as last resort
Naturally continuous for a given member
Fully dimensioned
With members on application
Not less than 2 linear inches in nominal thickness in the field
Not less than 4 linear inches – built-up or whole – in nominal thickness
At sheathing sheet joints to other sheets
Otherwise, at perimeters
Contain not more than 12% moisture content
On delivery to the jobsite
On application
On closing
Except preservative-treated wood products which shall contain not more than 19% moisture content
On delivery to the jobsite
On application
On closing
Determined to have been stored dry before being delivered to a site
Delivered to a site on other than a rainy day and
Stored on a site sheltered from natural elements
If graded, then not ripped to structural application
If engineered, may be ripped if appropriate adjustments are made to performance metrics given the member's post-rip dimensions
A rim boardor end or head joistshall be of solid, sawn lumber or engineered lumber
Shear wall shall be sheathed
Separated with framing clips
Fastened directly to a member
Fastened firmly and without bending and gapping to a member
Fastened with the full complement of nails or screws prescribed by the manufacturer
Applied in lieu of toed nails in fastening blocks and end and head joists, or rim boards, to subordinate structure
At plates, nails shall be applied one size above that specified for nonshear wall application
A shear wall sole plate or mudsill above concrete
Shall have a moisture impermeable membrane, e.g., galvanized steel, EPDM, peel-and-stick, etc., shall be applied continuous between sill atop foundation and the foundation top of face
A concrete foundation below a shear wall
Shall be tied on the vertical by not less than Grade 50-#5 deformed rebar
Which rebar hook shall be 3 linear inches up from the footingbottom of face
Which rebar shall be set on not greater than 16 linear feet centers in the field
Which rebar shall be set not greater than 1 linear foot from a terminus or change in footingdirection (both sides)
Which rebar shall number not less than two in any foundation segment
Which rebar shall extend into a foundation wall not less than 40 bar diameters, noting that if this last prescriptive presents the reinforcement above the wall top of face, then lower the footingdepth sufficiently to let 3/4 linear inch plus maximum aggregate size cover to wall top of face
Sill stock shall be labeled "KDAT" (a/k/a kiln dried after treatment)
An opening in a shear wall shall be reinforced
With not less than full-depth, solid blocking in line on horizontal with header(flush to header bottom of face) and top sill plate from opening to perimeter stud of the shear wall in both directions
Which blocking shall be below a continuous steel strap for tension not compression from across the wall from perimeter to perimeter
With continuous steel strap for tension not compression on the vertical in-line with the innermost jack stud extending from both top plates down to the sill plate(s)
Sheathing shall be fastened to the king studs either side (please note that metal hangers shall be in lieu of jack studs) with not less than 10d box nails on not greater than 4 linear inches center
In stepped foundations, cripple shear walls shall have connections concentrated on highest segment, notwithstanding alternative engineering
A strap shall be straight and true and not kinked, bowed, twisted, or bent
Shall be applied for tension and not compression
A shear wall post
If built-up, shall be stagger-nailed with 16d common galvanized at 6 linear inches on center
Shall be arranged in-line vertically wherever possible
Shall be not less in dimension than the post above it, notably including crawlspace cripple walls
Assure that metal fasteners in contact with preservative-treated wood are appropriately qualified for durability
PROHIBITEDS
In shearwall construction, there
Shall be no let-in bracing
Shall be no Oriented Strand Board, or OSB, or other particled board applied as sheathing
Shall be no sill anchor or other substitute for an anchor bolt
Shall be no nails with heads other than fully rounded, e.g., Sheather Plus by Stanley-Bostitch or similar
Shall be no nails other than common galvanized or their equivalent shank diameter.
Shall be no framing member that is
Standard or utility grade lumber
Including all lumber in quality less than #2
Lumber finger-jointed
Lumber end-jointed
Members scabbed
Members butted
Members spliced
Shall be no slots cut in a wall
Shall be no doubled panels on a given panel face
Shall be of no fasteners
Other than steel
Of type including screws of any sort
Shall be no plumbing conduit within a wall
Comment:In view of other prohibitions of wall mass amendments and other insults, this means that conduit of any sort shall not be permitted in shear walls. Note well that such prohibition might not extend to a centerlined bore for a water supply pipe or a small number of electrical cables
Shall be no strap tie-downs
Shall be no keyedfootingor cold-joint between foundation foot and placed wall, i.e., shall be footing and wall shall be monolithic
Shall be no prefab shear walls or bracing panels without the express advice and consent of the engineer of record, owner(s), and both general and supporting sub-contractor
Tie-down rod shall lean not greater than 1 linear inch on the horizontal for each foot of rod length; otherwise, replace the tie-down
Height-to-length ratios shall be respected, especially in re plate amendments of any sort, e.g., cable or water supply intrusion (again, even these minor insults should be and almost always can be avoided in shear walls), at a maximum of 3:1 without engineering an abundance of caution
Epilogue:Note well that the Journal of Light Construction article archives are an excellent source for a fuller presentation of both designing and building shear walls.
Before The Architect designs and drafts custom home plans nationwide. Its principals Ralph and Jean Pressel have worked hands-on together since the ‘60s in custom home design, drafting, consulting, plus building and repair in every major trade.Their plan sets are extraordinarily detailed; their clients' active involvement throughout is essential.
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