Introduction

For some time efforts have beenmade to promote Advanced Framing,also known as Optimum ValueEngineering (OVE). OVE is a seriesof choices, not a method of wood-frame construction.The basic ideain OVE is to “engineer” eachelement used, rather than simplyfollow techniques used in the past.Advanced framing is the optimumuse of wood framing; both from acost and building scienceperspective.

Advanced framing is not just a cost savings approach to building.It should not be equated withinferior construction. It alsorepresents a "green" buildingtechnique because it reduces thequantity of materials used in abuilding without compromising the intended use of the building.

In practical terms advanced framingmeans using less wood to frame a house. It eliminates wood whereit is structurally unnecessary orwhere its use is likely to causeother problems such as drywallcracks. Besides using less lumber,

advanced framing will reduce callbacks by not having the extra wood in the wall to cause drywallproblems. Drywall problems areusually caused by the differentialshrinkage of two different pieces of lumber nailed together.

Advanced framing is not a newidea. It was developed in the 1960sand fully complies with the NationalBuilding Code. However, becauseadvanced framing is seldomconsidered, builders may haveto rethink some of their standard

framing details. It is important tonote that special wind, seismic orsnow load conditions may requireadditional analysis and material, butthis will be specific to a particularhouse design and location.

etter buildingsBC A S E S T U DY N U M B E R 4 6

Advanced Framing

Case Study

Figure 1: Case study house

Designing

for Advanced

Framing

Advanced framing spaces framingmaterials at their most costeffective spacing—all studs, joistsand roof members at 600 mm (24 inches) on centre consistentlythroughout the house structure.To have the greatest impact,consideration of advanced framingshould begin at the planning stage.By designing in 600 mm (24 inch)modules, or in even dimensions itsimplifies the framing layout anduses less material. In addition, moreinsulation can be added due to lesswood in the building enveloperesulting in a more efficient andcomfortable structure.

If all floor, wall and roof framing is coordinated at the same spacing,the respective members beardirectly over each other. Dead andlive loads are thus transferreddirectly through the lower membersto the foundation, resulting in amore efficient structure thateliminates the need for someframing members.

Advanced framing principles were applied to the design of a small house to be built in theVancouver area.The two-storeyhouse has a footprint of 69.67 m2

(750 square feet) and a total floorarea of 139.35 m2 (1,500 squarefeet). (Figure 1)

Wall Framing

Traditional framing practices usewall studs placed at 400 mm (16 inches) on centre even thoughwider spacing is allowable whenconsidered from a structural andcode standpoint. Double top platesand three- and four-stud corners are also common.

The advanced framingapproach is to layout allframing on a 600 mm (24 inches)basis except wherestructural requirementsmay require narrowerspacing.Advancedframing eliminatesunnecessary use ofwood such as lintels innon-loadbearing wallsand cripples and doublestuds around windowsand doors.Aligningloads from floor joiststo studs below allowsuse of a single topplate. (Figure 2) Fewerstuds result in fasterassembly and a betterinsulated wall becausethere is less thermalbridging and morespace for insulation inthe building envelopecavity. More insulation in the walls reduces heat loss and possibly the size of the heating system.

When the location of door andwindow openings in the exteriorwall is coordinated with themodular stud spacing, it caneliminate or reduce the use ofcripples and jack studs, regardless of whether the walls areloadbearing.Where it is possible to use window sizes that fitbetween the studs, no addedcripples or lintels are required.At larger openings, a single studplus jack stud are required.

In a typical house with standardframing at 400 mm (16 inches) on centre, the area of all plates,studs, lintels, jack studs and cripplestuds can be as much as 23 percent of the exterior wall area. Usingadvanced framing techniques, withstuds spaced at 600 mm on centre,

and with unnecessary jack studs,cripples, and redundant studsremoved, the wood parts of thewall can be reduced to about 15 per cent of the exterior wall area.

Today 38 x 140 (2 x 6) framing is the norm in most regions ofCanada.A 38 x 140 mm (2 x 6) wall at 600 mm (24 inches) uses no more lumber than a 38 x 89 at 400 mm (2 x 4 at 16 inches), but is structurally superior and allowsfor more insulation. A 400 mm (16 inch) on centre modulerequires one extra stud for each1,200 mm (4 feet) of wall lengththat also requires more fastenersand labour to install.

With proper planning a number of cripples and jack studs can beremoved, especially in non load-bearing exterior walls. In manysituations they generally serve no structural purpose but occupyspace that could be insulated.

Figure 2: Alignment of framingelements: roof trusses beardirectly on studs and floor joistsdirectly below. No lintel requiredfor openings within stud spacing.

Thus a 38 x 89 mm (2 x 4) bottomplate can be used under a 38 x 140mm (2 x 6) stud which would becantilevered out 50 mm (2 inches).Once this is done, 50 mm (2 inches)of insulated sheathing can be appliedto the outside, over the rim joist or the foundation.This makes theoutside wall flush and thermallyprotects the building envelope.(Figure 4)

Exterior Wall

Corners

A three-stud corner, and in somecases four studs are commonlyused in standard framing practicealthough it is not structurallynecessary.The load on a cornerstud is about one-half that of aregular stud, so two-stud cornersare more than adequate to carrystructural loads.The third or fourthstud typically serves as backing forthe interior wall finish material,usually 12.5 mm (1⁄2 inch) thickgypsum board.The corner can beformed from the end studs in eachof the two wall panels that meet inthe corner. Eliminating the extrastud(s) means more insulation canbe installed in the corner to reducethermal bridging.

but it is not a problem today withthe standard use of 12.5 mm (1⁄2 inch)gypsum board.

It is also worth noting that extraframing can cause drywall crackingor nail popping as a result ofdifferential shrinkage or movementof the individual pieces of wood.This is especially noticeable atcorners, where shrinkage andwarping of studs in oppositedirections can place stress on the drywall joints that are weaker.

Wall Plates

A single top plate can be usedwhere the joists or trusses aboveare aligned directly over the framingmembers. Metal connector platesmay be needed to tie the top platestogether.Where single top platesare used, the stud length and wallheight must be considered toobtain the most cost effective useof gypsum board finishing materialsand to avoid excessive trimming.

The bottom and top plate can bereduced in size.This will use lesslumber and improve the energyefficiency of the structure.Thisworks especially well with 38 x 140(2 x 6) wall construction, because for most applications 89 mm (31⁄2 inch) wide plates provideadequate structural support.

Jack studs are usually the easiest to eliminate because they generallydo not support significant loads,especially for small windows.Aswell, there is usually no need for as many cripples as are usually used.Most framers automatically place acripple at either end of the bottomwindowsill plate regardless thespacing of framing.When cripplesare needed, they only have to be of 38 x 89 mm (2 x 4) material.However, it may be necessary toconsult with a structural engineerfor specific design conditions.(Figure 3)

For the home in this case study,the location and size of door andwindow openings were coordinatedwith the stud location on at leastone side of the opening whereverpossible. Conventional framingpractice would have used 204 studsfor the exterior walls on both levelsfor this house.Advanced framingpractices will reduce this to 152 studswhich represents a 25 per centreduction, for a cost saving of$151.50 for the lumber alone.Thissaving does not even include laboursavings due to less materialhandling.

A concern sometimes made is that the wider spacing will createdrywall problems.This may havebeen a problem in the past when9.5 mm (3/8 inch) drywall was used,

Figure 3: Unnecessary jacks and crippleseliminated; fully insulated exterior corner; openingsaligned with stud spacing module.

Figure 4: 89 mm (31⁄2 inch) bottom plate in a 140 mm (6 inch) wall.

Even where 38 x 89 mm (2 x 4)framing must be used toaccommodate services or doortrim, the 600 mm (24 inch) spacingreduces the quantity of lumberused.

Openings in non-loadbearinginterior partitions such as passagedoors and closets have no particularstructural requirements.Thus, theopening may be single-framed withone stud at each side and a blockacross the head. No lintel or jackstuds are required, nor are cripplestuds required over the head. It isadvisable to install horizontalblocking using cut-offs (waste) on either side of the opening usingsingle studs to provide additionalstrength and rigidity.This will helpeliminate the twisting of the studthat may occur, and to provideextra strength that may be neededfor hardware. (Figure 6)

Eliminating

Partition Posts

Where interior partitions meet the exterior wall a “partition post”is typically built into the exteriorwall to provide backing for theattachment of partitions. Exceptwhere the post is part of anengineered design, for example to carry a point load, there is no structural requirement foranchorage of partitions to theexterior wall.The advancedframing approach is to use flathorizontal blocking, using cut-offs,spaced at 600 mm (24 inches),between the adjacent studs of theexterior walls, to which theinterior framing can be attached,and also as a backing for interiordrywall.This allows the stud cavityto be fully insulated (althoughblocking will affect insulationdepth), and leaves no uninsulatedspaces, as often happens in theseareas. (Figure 7)

Drywall clips can be used tosupport the gypsum board. (Figure 5)The gypsum board is attached to aone-corner stud, while the sheet on the adjacent wall is kept in placeby drywall clips that are attached to the same stud.This also reducesthe potential of call backs to repairdrywall because a floating joint hasbeen created.

In the case study house, which hasa simple rectangular plan with fourcorners, a total of eight studs areeliminated at the corners by using a two-stud corner framing detail.

The calculated overall R-value ofthe 38 x 140 (2 x 6) exterior wallfor this house framed usingadvanced framing (ignoringwindows and doors) is about RSI 3.03 (R-17.2) when glass fibreinsulation is used.The overall R-value of the same 38 x 140 (2 x 6)wall if framed with conventionalframing practices is only about RSI 2.81 (R-16.2) because whencompared to glass fibre insulation,wood is a poor insulator.The RSIvalue of wood is only about 0.21 (R 1.25 per inch).

Thus, in addition to the lowermaterial cost for the advancedframing because of reduced lumberusage, advanced framing canincorporate more insulation toprovide a better insulated buildingassembly.

Interior Wall

Framing

The primary function of non-loadbearing interior partitions is to divide interior space andprovide a desirable degree ofprivacy. Because structural loads are small, the size of the framingmembers may be smaller, such as 38 x 64 mm (2 x 3 inch) woodstuds, and if the 600 mm (24 inch)module is used, this will result insignificant reduction in lumber used.

Figure 5:Two-stud exterior corner with drywall clips

Figure 6: Opening in interior partition.Horizontal blocking provides backing to hardware.

Figure 7: Interior partition wall at exterior wall.Horizontal blocking supports interior partitionframing, insulation runs across behind blocking.

Standard carpentry practice is touse a uniform 38 x 235 mm (2 x 10)framing member for all lintels.Thuseach 1,200 mm (4 foot) window inthis case study design that avoids a lintel over the window representsa material saving of $6.27, plus lesslabour time for materials handling.

Conclusion

Conventional wood-frame designand construction practices have not changed greatly over the last 25 years.Traditional constructiongenerally uses much more materialand labour than may be requireddue to perceived increasedstructural rigidity, convenience or for assumed code compliance.Material and labour waste iscommon.The additional materialsand labour may serve no purposeand add appreciably to the cost of a project.

By careful review of the design andstructural requirements, this smallhouse can be framed with 52 fewerstuds, less plates, and 3 fewer piecesof 38 x 235 mm x 2,400 mm (2 x 10 x 8 feet), for a materialsavings of $232.35. This would alsomean labour savings as there is lessmaterials handling and assemblyinvolved. In addition, the improvedeffective insulating value will meanlower energy costs for the houseover its life.

Lintels

An analysis of the plans beforeconstruction begins may determinethat with some minor changes one could save on materials byeliminating materials and by placinglintels in alternate locations. Lintelscan be eliminated in gable end wallswhere there is no load or wheretrusses are parallel to the wall inwhich the lintel is located. Otherareas where lintels can be eliminatedare if windows are placed within a single stud space in the wall.

It is also possible to move the lintel up above the top plate in a two-story design when used inconjunction with the rim joist, thuseliminating one ply from the header.The applicability of this detail willrequire a review of the loading andspan of the lintel.

In this case study house, four windowsare located in non-loadbearing walls,so no lintels are required for them.Three windows that do requirelintels will be framed with a doubledrim joist over the window, avoidingthe use of a separate lintel, thusreducing the amount of lumberneeded.This approach also allowsmore insulation to be placed in thewall cavity, as there is less lumber,but does not result in a reduction of insulation space in the floor joistspace, as the full depth can still beinstalled in the joist space.

Floor Framing

Depending on the loads and spans,floor joists can also be spaced at600 mm (24 inches) on centre.This reduces the number of joists by about one third compared with 400 mm (16 inch) spacing.Increasing floor joist spacing mustbe carefully assessed in order toensure that adequate floor stiffnessis maintained. Floor sheathingthickness will also have to beupgraded to yield equivalentperformance.Typically, this meansusing a 19 mm (3/4 inch) thicksubflooring instead of 15.8 mm (5/8 inch) subflooring.

In the case study house the spansallow the floor joists to be spaced at 600 mm (24 inches) on centre, so14 joists could be saved. However,the cost savings of $150.00 arematched by the additional cost ofthe thicker plywood needed, so it was decided not to select thewider spacing as an option.Theeconomics have to be assessed for each situation.

Non-loadbearing partitions that run parallel with the floor joists do not require double floor joistsunder them.They can be supportedon 38 x 89 mm (2 x 4 in) blockingbetween adjacent joists.The blockingmust not be spaced more than 1.2 m (4 ft) apart.

Reducing Built-up

Posts

In a 38 x 140 mm (2 x 6) wall wherea built-up post is required to carry a built-up beam in the floor above,typically a 38 x 140 mm (2 x 6)built-up post is used. However, a 38 x 89 mm (2 x 4) built-up postmay be enough to carry the loads.Using 38 x 89 mm (2 x 4) framing inthis application would save materialand allow for insulation to be installedbehind the post, thus reducingthermal bridging in the wall.

Savings for case study

Element Material saving Cost savings

Studs 400 board feet $ 151.60

Lintels 26 board feet $ 6.27

Plates (single top plate) 156 board feet $ 55.33

Plates (89 mm (31⁄2 inch)sill plate) 48 board feet $ 19.15

Total $ 232.35