Before The Architect - Attaching A Deck

Attaching A Deck

BEFORE THE ARCHITECT – DREAM HOME DESIGNING BACKGROUND – CUSTOM HOME DESIGN ARTICLES

HARMONY IN Home design - Attaching a deck

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Of physical safety, efficiency, convenience, durability, and aesthetics — safety rules. Before The Architect

INTRODUCTION

This article is about crucial safety in design and construction of attaching a deck generally and specifically attaching a deck ledger.

a swell way to wreck a deck? Break things? Hurt people?

attach the ledger to house structure and the deck structure to the ledger.

if it's a tub deck, attaching the deck - at its crux, attaching a ledged - is all the more important; however, every deck's attachment is important

and do not forget a full set of deck knee braces to dampen lateral movement . . . don't you dare forget

What's in securely attaching a deck to a house? Please read on. This is about NOT breaking things and NOT hurting people.

DREAM HOME DECK DESIGN SAFETY, ATTACHING DECK TO HOUSE VIA ATTACHING A LEDGER

Bolts shall be applied as fasteners for a attaching a ledger to house structure

galvanized – bolt, washers, and nut

not less than 5/8 linear inch diameter

not greater than 16 linear inches on center, preferably not greater than 12 linear inches on center

pre-drilled holes not less than 1/32 linear inch and not greater than 1/16 linear inch larger than bolt diameter

to barely pock the ledger face exposed around the washer

galvanized lag screws must be used instead of carriage bolts, then

2 such screws shall be applied sequentially

screw shall penetrate

less than the depth of the in-lieu

less than 1/2 linear inch clear-through where applicable

a hole predrilled to unthreaded depth and in diameter not less than 1/32 linear inch and not greater than 1/16 linear inch larger than the unthreaded shank’s diameter

a hole predrilled for the threaded depth in diameter not less than 1/32 linear inch and not greater than 1/16 linear inch narrower than the threaded shank’s root diameter

screw shall be run home

wrenching and not by hammering

more than 1 such screw shall be applied in a 4 linear feet span

to barely pock the ledger face exposed around the washer

Comment: This designer might relax this last guidance about lag screw spacing where a deck is fastened to structure on more than one side. All other design and construction guidance herein under in regard to attaching a deck to house structure prevails as is.

In any case – whether screw or bolt

shall be in conformance with not less than applicable standards in the Fastening Design Standards, section head below, GENERAL SPECIFICATIONS FOR FASTENERS TO MEMBERS PRESERVATIVE-TREATED W/ ALKALINE COPPER QUAT (ACQ Types A and B), COPPER AZOLE (CBA-A & CA-B). etc. applicable to wood deck members, mudsills and other members in contact with concrete, e.g., pocketed beams, floor joists, floor trusses, etc. or subject to atmospheric exposure, e.g., porch posts, framing lumber, plywood, furring strips, mouldings, etc.

to which newer preservatives shall include

of aluminum flashing

optionally of either stainless steel or copper flashing

If borate (a/k/a DOT, or disodium octaborate tetrahydrate) is the wood preservative

wood so preservative-treated shall be applied only in persistently dry areas, e.g., most mudsills or sill plates, unless otherwise noted and

special materials are required either to coat or comprise the fasteners, flashings, etc. beyond those applied either to untreated lumber or CCA (chromated copper arsenate)-treated lumber

In any case – whether screw or bolt – ledger shall be offset to structure ½ linear inch by stacked washers over moisture impermeable barrier material

Comment: For a larger view of wood preservation variously treated, this house designer suggests you consider “Wood Preservation" by Rebecca E. Ibach at http://www.treesearch.fs.fed.us/pubs/7156

Shelves set below ledgers, joists, beams, etc. shall not be considered structure

Wooden Deck Ledger, Elevation and Section in Elevation

Key to abbreviations: ABS=ABSolutely; APX=APproXimately; ABV=ABoVe; BEL=BELow; BOT=BOTtom; CB=Carriage Bolt; COM=COMmon; CONT=CONTinuous; DBL=DouBLe; DK=DecK; E.=East; EL=Elevations; EQ=Equal; EXG=EXistinG; EXT=EXTerior; FLS=FLaShing; FSN=FaSteN; GLV=GaLVanized; HOR=HORizontal; INT=INTerior; JST=JoiST; NLT=Not Less Than; NTS=Not To Scale; PT=Preservative-Treated; RFL=Rough Floor Level; S.=South; SHTG=SHeaThinG; STRC=STRuCture; TOF=Top Of Face; TYP=TYPical; VERT=VERTical; W=West; X=eXcept

Comment: “Rim board" here is not meant to identify genuine 2 linear inches x dimensioned lumber applied as end and head joists, or “ribbon", or “band". Rim board here is meant to identify anything that isn’t 2 linear inches x dimensioned lumber applied as end and head joist, or “ribbon", etc….that specifically means OSB and other particle-component building materials. These materials, unamended by substantially incremental structure, are, in the AG’s opinion, unsuitable for direct support of ledgers.

Structure and fasteners shall be protected from natural moisture by

only preservative-treated lumber

flashing

	not less than 6 linear inches concealed between superior sheathing and house wrap to
	90° turn to cover the ledger top of face and abut to the structure to which it is fastened and
	from the exterior side of face of the ledger not less than 2 linear inches and at approximately a 45° deflection downward

to thoroughly seal bolts and screws and their washers from moisture intrusion

ledger from exterior wall by not more than ½ linear inch by applying galvanized washers as shims – see www.jlconline.com/deckledgers

Joist and beam hangers to ledger shall not be less than in full-depth specification in conformance to joist and beam nominal depth, absolutely

Comment: “Short" hangers distribute joist and beam bearing unevenly to the ledger, relying on only a part – a lower part – of the ledger for support.

This is analogous to an unsupported back-cut into a joist at a plate or beam joint, or resting rafter heels on interiors to a double top plate top of face. Air is not a structure. Immediately above, the illustration of a ledger specification reflects our ledger design standards.

Particle rim board shall be a prohibited material for fastening a ledger without express compensations to structure as developed by a qualified engineer or, in some cases, a master carpenter

Comment: If this ledger design guidance is not practical in application - notably, for some house remodeling projects- please consider this alternative method of deck construction, see “Attaching Deck Ledgers" by Cheryl Anderson, Frank Woeste, and Joe Loferski in the August 2003 issue of The Journal of Light Construction, notably addressing “Detail 4: Deck Building Supported with Posts" and related text.

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[ Home ] [ Up ] [ Attaching A Deck ] [ Deck Knee Braces ] [ Joist Framing ] [ Roof Framing ] [ Roof Planning ] [ Sheathing ] [ Stud Frame Wall ] [ Shearwalls ]

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