BuildaFloor
Description
Floorsareanintegralpartofresidential construction andmust be builtto specifications thatmeetbuilding code requirements.Inthis Activity Plan,studentswill be cutting andassemblingcomponentsof a wood frame floor (including floor joists, rim joists,andsheathing)accordingtodrawings or specifications.
LessonOutcomes
Thestudentwill be ableto:
•Identify floor framingcomponents
•Extract information from thedrawingswithrespecttosizeand location ofcomponents and/or openings
•Demonstratesafeuseofhandandpowertools
•Useappropriatelayouttools
•Construct a basic floor withjoists, rim joists,andsheathing
•Recognizehowto check and mark crown on joists
•Gaintheskills necessary toapplytongueandgroove(T&G) plywood
Assumptions
Thestudentis:
•Familiarwithsafeuseof a portable circularsaw
•Familiarwithbasictoolsformeasurement(tapemeasure)andlayout(framingsquare)
•Familiarwithextractinginformation from drawings
•Awarethat floor systemsmustbear on beams,walls, or othersignificantstructuralmembers
Terminology
Bow:warpingalongthelengthofthefaceofapieceoflumber. Bowistypicallynotaconcernforfloorjoistsbutthetermcanbediscussedtoprovidestudentswithanunderstandingofanotherissueoftenseeninlumber.
Figure1—Bowinlumber
Boxjoists:joistsspecificallycuttoformanopeninginafloor(typicallyaroundastairopeningorother components).
Ledger
Boxjoist
Headers
Cutjoists
Boxjoist
Offsetbetweenjoistcutline
andceilingcutout
Figure2—Commonheaderandboxjoists
Crown:warping by arching (onedge)ofapieceoflumberduetodryingconditions.Thecrownonafloorjoistshould always beplacedarchingup toward thetopofthestructure.
Figure3—Crowninlumber
Doublejoist:twojoistsscrewedorboltedtogethertocreateastrongerjoist.
Floorfasteners:nailsorscrewsusedtofasten thesubfloorplywoodtothefloorjoists. Typicalfastenersincluderingnails(smalldirectionalringsontheshankto prevent thenailfromworkingbackoutoncedrivenin); galvanized nails (zinc treatedtoprovidearoughfinishresultinginveryhighcorrosionresistanceandto prevent thenailfromworkingbackout);andsubfloorscrews(treated withzincto prevent corrosionandbreakage).
Floorjoist:oneinaseriesofparallelframingmembersthatsupportafloorload.Joistsaresupported by beamsorbearing walls.
Figure4—Isometric viewofa typicalfloor showingfloor joistsand rimjoists
Flooropening:aholeoropeninginafloor, roof,orplatformthatmeasures12" ormoreinitsleastdimension,wideenoughtopermitapersontofallthrough.
Floorsheathing(sheeting):plywood,orientedstrandboard(OSB),orlumberusedtocloseupfloorsbeforetheinstallationoffinishmaterialsonthesurface.Thisisalsoknownas subflooring.Tongueand groove plywood(T&G)isrecommended.T&Gplywoodisspecificallydesignedsothateachpiecehasaslot (the groove)cutallalongoneedge,andathin,deepridge (the tongue)ontheoppositeedge (Figure 5).Thetongueprojectsalittlelessthanthedepthofthe groove.
Twoormorepiecesthusfittogethercloselywithless movement orflexing.
Figure5—Tongueandgrooveplywood
Headerjoist:ajoistpositionedhorizontallybetweentwolongerjoistsinordertoframearoundanopening.
Joisthanger:ametal bracket usedtoattachandsupporttheendsofawoodjoisttobeamsorotherstructuralcomponents.
Rimjoist:thefinaljoistthatattachestotheendoftherowofjoiststhatsupportafloororceiling.Arimjoistformstheoutsideedgeofthe box that makes upthe floor.
EstimatedTime
2–6hours
Thetimeforthis activity willdepend on thefamiliarityofstudentswithtoolsandthe scope oftheproject (e.g.,sizeandshapeoffloor,whetheritincludesopenings,availabilityoftools,spaciouswork environment).
RecommendedNumberofStudents
20,based on theBC TechnologyEducators’ Best PracticeGuide.Theidealis16,workinginteamsof2–4students,depending on thesizeand scope ofthefloor(s)beingconstructed.
Facilities
Technologyeducationshopfacilityisideal,aswellas a largesecureoutdoorspacetowork.
Tools
•Portable circularsaws
•Extensioncords
•Tapemeasures
•Combinationor speed squares
•Hammers or pneumaticnailers
•Sledgehammers(requiredtoapplyT&Gflooring)
•Framingsquares
•Levels
•Nail bars
•Aprons
•Hardhats,eyeprotection,andhearingprotection
Materials
•2×?"materialforjoists(2×4"maybeadequate,but 2×6",8",10", or12"may be moreappropriatedepending on thesizeoftheprojectandjoistspan)
•Floorsheathing (plywood or OSB)
•3" common brightnails,fornailing floor joists
•2" common ring nails or 2"galvanizednailsfornailing floor sheathing.Ifthesheathingmaterialisto be reusedat a laterdate,itisrecommendedtouse2"subfloorscrewsforeaseofremoval.
Resources
Graphic/photoof floor systemwith cross section aswellasisometricdrawing.
Sampledrawingsofthe floor should be provided(possiblyas a standalone,andas a portionofa shed-style project if the floor ispartof a largerproject).
Activity
1.Reviewterminologyandsafepractices.
2.Determinethesizeandshapeofthefloor,anddeterminethepositionofany floor openings(forthis project itisrecommendedthat a simple floor withoutopenings be built).
13¾" / 14½" / 13¾"Attach (10) 8' × 2" × 6" joists to (2) 12'× 2" ×6" rim joists resting onthe (3) 4" × 6" beams.Install blocking betweenjoists.
7 at 14½" and the two outside at 13 ¾"
Figure6—Sample drawingillustratingbasic measurementsand spacingbetween joistsfor afloor
3.Generate a materiallist,includingthenumberofjoistsandsheathingrequirements.
4.Establish a positioningstrategyforthe floor to be built(cinderblocksunder corners, etc.).Thiswoulddepend on theshopfloor,mezzanine, or otherbuildingareaavailable.
5.Select lumberto be usedforjoistsandphysicallyexamineeach piece todetermineanycrownpresent.Thecrownedgeshould be markedwith a large V to identify it,andallcrownsshouldfaceupwhenfastening.
6.Cutthe rim joiststolengthusing a portable circularsaw or mitresaw.
7.Transferthejoistlayouttothe rim joists.Ensure correct spacingof16" from theoutsideofedgeofthefirstjoisttothecentreofthe second joistand16"spacing OC foreach
continuingjoist.Thespacingshould be markedoutusing a speedsquare or framingsquarewith a lineandan X toindicatethesideto which thejoistwill be fastened.
8.Cutsthejoiststolengthwith a portable circularsaw or mitresawandnailwith3" commonnailsbetweenthe rim joists,makingprovisionsforany floor openings.
9.Ensurethe floor joistsaresquarebymeasuringthe floor diagonallyandadjustingasnecessary.
10.Apply floor sheathing.(Itisrecommendedthatsheathing be appliedusingscrewsinordertoremoveandreusethemateriallater.)Sheathingsheetendsmustoverlaptothecentreofthejoistsand be staggered if morethanonerowisapplied(Figure7).
TheT&Gsheathingisappliedbylayingdownthe plywood withthetongueedge insertedinto thegrooveofthepreviouslyappliedsheet. A long 2×4"islaidflat on thejoistsagainstthegroovesideandtappedwith a sledgehammertodrivethetonguetightlyintothegrooveof theadjacentsheet. (The 2×4"allowsforevenpressureand preventsdamagetothe
edgeoftheplywood.)
" minimum gap at panel endsand edges or followmanufacturerrecommendations.
T&G edges should be buttedlightlytogether.
Figure7—Typicalsheathingplacementwithstaggeredendjoints
11.Itmust be determinedinadvance if the floor isgoingtosimplyrestuponanexistinglevelfloor, or if itisgoingtobearuponpierblocks,beams, or establishedfoundationwalls sothatstudents can maketheappropriateaccommodations.
EvaluationGuidelines
Thestudent:
•Usesappropriatesafetyequipmentandprocedures
•Selects appropriatetool(s)forthetask
•Sequencesoperations correctly
•Producesaccuratelycutand correctly laidoutframingcomponents
•Correctly assemblesandfastenstogetherframingmembers
•Producessystemsthataresquare,plumb,and/orlevelasrequired
•Cutsandappliessheathing correctly withtheappropriatefasteningsystem
•Exhibitsoverallprofessionalquality(flushjoints,nobentnails,appropriatematerialqualityselection—e.g.,crownsandbows)
•Maintains a tidy work environment.Thisincludesremovingscrapmaterialsandstoringtoolsandmaterialsappropriately.
OptionalExtensionActivity
Itmay be beneficialtoincludediscussionofthefollowing:
•Joisthanger: a metaldevice shapedlike a“U,”used to connecta joistand beamat rightanglestoeachother.
•Bridging(blockor cross):a method of lateral bracing between joists for stiffness,stability,andloaddistribution.
•Tailjoist (tailbeam):a shortbeam or joistwithoneend setin a wall andtheothersupported by a header.