Light Frame Light Frame ConstructionConstruction

HistoryHistory Light wood frame construction invented in 1830 Light wood frame construction invented in 1830

in Chicago by George Washington Snowin Chicago by George Washington Snow He recognized that closely spaced vertical He recognized that closely spaced vertical

members used to fill space in walls of heavy members used to fill space in walls of heavy timber was strong enough to carry weightstimber was strong enough to carry weights

Small boards and framing members became Small boards and framing members became inexpensive due to new milling practicesinexpensive due to new milling practices

Machine made nails became cheap compared to Machine made nails became cheap compared to hand forge nailshand forge nails

Called balloon frame because it seem so thinCalled balloon frame because it seem so thin

Balloon FrameBalloon Frame

Joist – FloorsJoist – Floors Studs – WallsStuds – Walls Rafters – sloping Rafters – sloping

roofsroofs DisadvantagesDisadvantages

• Fire strips requiredFire strips required• Studs are to long to Studs are to long to

be erect efficientlybe erect efficiently

Platform FramePlatform Frame FloorFloor Wall – Load bearingWall – Load bearing FloorFloor Wall – Load bearingWall – Load bearing Attic/roofAttic/roof AdvantagesAdvantages

• Short studsShort studs• Automatic fire stopsAutomatic fire stops• Convenient working surfacesConvenient working surfaces

DisadvantagesDisadvantages• Each platform constitutes of a Each platform constitutes of a

thick layer of wood whose thick layer of wood whose grain runs horizontallygrain runs horizontally

• Leads to vertical shrinkage –Leads to vertical shrinkage –leads to distress in exterior or leads to distress in exterior or interior finish surfacesinterior finish surfaces

Platform Frame SheathingPlatform Frame Sheathing Is the key component for platform Is the key component for platform

framingframing• The end nails that connect the The end nails that connect the

plates to the studs have little plates to the studs have little holding power against uplift of the holding power against uplift of the roof by wind but the sheathing roof by wind but the sheathing connects the frame into a single connects the frame into a single strong unit from foundation to strong unit from foundation to roof.roof.

• The rectilinear geometry of the The rectilinear geometry of the parallel framing members has no parallel framing members has no useful resistance to wracking by useful resistance to wracking by lateral forces such as wind, but lateral forces such as wind, but rigid sheathing panels or diagonal rigid sheathing panels or diagonal sheathing boards brace the sheathing boards brace the building effectively against a building effectively against a surface to which shingles boards surface to which shingles boards and flooring are nailed for finished and flooring are nailed for finished surfaces.surfaces.

Foundation for light Frame Foundation for light Frame StructuresStructures

Foundations for light framing originally Foundations for light framing originally made of stone or brink – are now made in made of stone or brink – are now made in most cases of site cast concrete, most cases of site cast concrete, concrete block masonry or preservative concrete block masonry or preservative treated woodtreated wood

Concrete and masonry foundations are Concrete and masonry foundations are highly conductive of heat and usually highly conductive of heat and usually must be insulated to meet code must be insulated to meet code requirements concerning energy requirements concerning energy conservation.conservation.

Wood foundation is easily insulated in Wood foundation is easily insulated in the same manner as the frame of the the same manner as the frame of the building it supportsbuilding it supports

Further advantages claimed for wood Further advantages claimed for wood foundations are that they can be foundations are that they can be constructed in any weather by the same constructed in any weather by the same crew of carpenters that will frame the crew of carpenters that will frame the building and they allow for easy building and they allow for easy installation of electrical wiring plumbing installation of electrical wiring plumbing and interior finish materials in the and interior finish materials in the basement.basement.

Establishing the position, shape Establishing the position, shape and size of buildingand size of building

Details of FoundationsDetails of Foundations

Planning the framePlanning the frame Architectural floor Architectural floor

plans serve to indicate plans serve to indicate the locations and the locations and dimensions of all walls, dimensions of all walls, partitions and partitions and openingsopenings

Exterior elevations are Exterior elevations are drawings that show drawings that show the outside faces of the outside faces of the building with the building with vertical framing vertical framing dimensions indicated dimensions indicated as required.as required.

Sections are also Sections are also drawn that cut drawn that cut completely through completely through the building showing the building showing the the

Erecting the FrameErecting the Frame Notice the basic simplicity Notice the basic simplicity

of the building processof the building process• A platform is built walls A platform is built walls

are assembled horizontally are assembled horizontally on the platform and tilted on the platform and tilted up into place and another up into place and another platform or a roof is built platform or a roof is built on top of the wallson top of the walls

• Work is accomplished Work is accomplished without the use of ladders without the use of ladders or scaffolding and or scaffolding and temporary bracing is temporary bracing is needed only to support the needed only to support the walls until the next level of walls until the next level of framing is installed and framing is installed and sheathed.sheathed.

Attaching the frame to the Attaching the frame to the foundationfoundation

The sill preferably preservative treated or The sill preferably preservative treated or naturally decay resistant wood is bolted to naturally decay resistant wood is bolted to the foundation as a base for the wood the foundation as a base for the wood framing .framing .

A single sill is all that is required by most A single sill is all that is required by most codes but in better quality work the sill is codes but in better quality work the sill is often doubled for greater stiffnessoften doubled for greater stiffness

The top of the foundation is usually The top of the foundation is usually somewhat uneven, so at low spots the sill somewhat uneven, so at low spots the sill must be shimmed with wood shingle must be shimmed with wood shingle wedges to be able to transfer loads from wedges to be able to transfer loads from the frame to the foundationthe frame to the foundation

A compressible fibrous sill sealer should be A compressible fibrous sill sealer should be inserted between the sill and the inserted between the sill and the foundation to reduce air infiltration foundation to reduce air infiltration through the gap.through the gap.

The normal foundation bolts are sufficient The normal foundation bolts are sufficient to hold most buildings on their to hold most buildings on their foundations, but tall frames in areas foundations, but tall frames in areas subject to high winds or earthquakes may subject to high winds or earthquakes may require more elaborate attachments.require more elaborate attachments.

Floor Framing and BridgingFloor Framing and Bridging The standard joist spacing are 16 The standard joist spacing are 16

or 24 o.c., measuring from center or 24 o.c., measuring from center tot center of the joiststot center of the joists

Any of these spacing Any of these spacing automatically provides a joist at automatically provides a joist at every panel endevery panel end

Sub flooring should be glued to Sub flooring should be glued to the joists to prevent squeaking the joists to prevent squeaking and increase floor stiffnessand increase floor stiffness

Plywood and OSB panels must be Plywood and OSB panels must be laid with the grain of their face laid with the grain of their face layers perpendicular to the layers perpendicular to the direction of the joists because direction of the joists because these panels are considerably these panels are considerably stiffer in this orientationstiffer in this orientation

Sheathing and sub flooring panels Sheathing and sub flooring panels are normally manufactured 1/8”are normally manufactured 1/8”

Bridging which is cross bracing or Bridging which is cross bracing or solid blocking between joist at solid blocking between joist at midspan in a tradional feature of midspan in a tradional feature of floor framingfloor framing

Floor Framing and Bridging 2Floor Framing and Bridging 2 Its function is to hold the joists Its function is to hold the joists

straight and to help them share straight and to help them share concentrated loadsconcentrated loads

Although many building codes no Although many building codes no longer require bridging, it should be longer require bridging, it should be used on better quality buildings used on better quality buildings because it makes a noticeable because it makes a noticeable difference in the rigidity of a floor.difference in the rigidity of a floor.

Where needs of joists butt into Where needs of joists butt into supporting headers as around stair supporting headers as around stair openings and at changes of joist openings and at changes of joist direction for projecting bays end nails direction for projecting bays end nails and toe nails cannot carry the full and toe nails cannot carry the full weight of the joists and sheet metal weight of the joists and sheet metal joist hangers must be used.joist hangers must be used.

Manufactured I joists and floor trusses Manufactured I joists and floor trusses are increasingly used in place of sawn are increasingly used in place of sawn joist because they can span farther joist because they can span farther between supports and they tend to be between supports and they tend to be straighter.straighter.

Wall framing Sheathing and Wall framing Sheathing and BracingBracing

Some building codes require Some building codes require blocking to be installed at the blocking to be installed at the mid height of the studs in wall mid height of the studs in wall frames that are taller than 8 frames that are taller than 8 ft. The purpose of this ft. The purpose of this blocking is to stop off the blocking is to stop off the cavities between studs to cavities between studs to restrict the spread of fire.restrict the spread of fire.

Headers over window and Headers over window and door openings must be sized door openings must be sized in accordance with building in accordance with building code criteria. Typically, a code criteria. Typically, a header consists of two header consists of two nominal 2 inch members nominal 2 inch members standing on edge separated standing on edge separated by a plywood spacer that by a plywood spacer that serves to make the header as serves to make the header as thick as the depth of the wall thick as the depth of the wall stud.stud.

Roof FramingRoof Framing

Pitch is specified as a Pitch is specified as a ratio of rise to runratio of rise to run

Rise is the vertical Rise is the vertical dimension and run is dimension and run is the horizontalthe horizontal

In the united states In the united states pitch is usually given pitch is usually given on the architects on the architects drawings as inches of drawings as inches of rise per foot of runrise per foot of run

Prefabricated framing AssembliesPrefabricated framing Assemblies Roof trusses and floor trusses Roof trusses and floor trusses

find widespread use in find widespread use in platform frame buildings platform frame buildings because of their speed of because of their speed of erection, economy of material erection, economy of material usage and long span.usage and long span.

Most are light enough to be Most are light enough to be lifted and installed by two lifted and installed by two carpenterscarpenters

Manufactured wall panels Manufactured wall panels have been adopted more have been adopted more slowly than roof and floor slowly than roof and floor trusses, except by large trusses, except by large builders who mass market builders who mass market hundreds or thousands of hundreds or thousands of homes pre year.homes pre year.