Roof Planning

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BEFORE THE ARCHITECT DREAM HOME DESIGNING BACKGROUND UNIQUE HOME DESIGNING ARTICLES

ROOF PLANNING A RAFTER ROOF

By Before The Architect  Copyright 2003-2007 Before The Architect

 

Be prepared to be lucky and to be unlucky.  We sometimes refer to this precept as knowing which train to board.  In this metaphor, lucky trains don't stop at one's station often in a lifetime, unlucky ones do.  Dont stand there waiting; keep moving.  Think about this all the time.

Before The Architect

ROOF PLANNING A RAFTER ROOF 

INTRODUCTION

    This e-article is about designing custom dream home roof planning a rafter roof, including pictures and text 

RAFTER ROOF PLANNING PICTURES & TEXT

Comment:  Nothing confuses and confounds more than roof planning for a rafter.  In this custom dream home designer's opinion, if it's not drawn in 3-dimensions, then it may not be well understood.  For some roofs, 3-dimensionality isnt needed.  For others, its demanded.

Again in this dream home designer's opinion, Autocad doesn't make it easy on the dream home designer (as, for example, does Chief Architect):

bulletLines must meet exactly in lengths and vectors
 
bulletImporting stock plans drawings can diminish or outrightly destroy isometric viewing
 
bulletStandard views of objects can overwrite and otherwise bedevil perspective
 
bulletElevations can tease out tantrums of "what's that line?" and "is that in foreground or covered up?"
 
bulletHatches to get better sense of depth and slope are limited to 3- and 4-sided flat planes. 
 
bulletA roof plans for a rafter roof planning shall define 
bulletSlope
bulletType
bulletGable
bulletHip
bulletShed
bulletRound
bulletValley
bulletRegular (default)
bulletIrregular
bulletRidge
bulletGable
bulletHip
bulletRising
bulletCricket siting
bulletTop plate lines relative to rooflines
bulletCross-reference to identify attic ventilation requirements
bulletCross-reference to identify water runoff requirements
bulletDepth of overhangs
bulletRafter endcuts
bulletSquare cut
bulletLevel cut
bulletPlumb cut
bulletFlares
 
bulletHerewith, a Rafter Roof Planning sheet example, noting that no two are identical 

Rafter Roof Planning, Plan View 

KEY:

A = a 1-off study of section in elevation to clarify if not simplify the several relationships between house top plates and roof intersections, including statements of design objective and design guidance by way of commentary on how this section came to pass and why 

B = roof design and construction notes, including but not limited to: materials qualifications for lumber and sheathing; deflection performance limits; approval process; fastening generally; moisture barriers; bracing; fastening specific to roof trusses; raised heels; etc. 

C = specific guidance in re design and construction, including but not limited to: overhangs of eaves, rakes and gables - both main and dormer; rafter tail style; member spacing and in-line siting; sheathing thickness and quality; radiant barrier application.  Also: dimensions uninterruptedly between roof deck articulations at eaves, rakes, hips, and ridges; identification of elements including gable rake and gable ridge, eaveline, shed rake and shed ridge, raking cornice, regular and irregular valleys; slope rate and direction for each roof plane; roof finish clad; dormer framing method; primary and secondary ridges; rising ridges; intersecting ridges, roof-dependent top plates; etc. 

D = key 

E = notice of residential contractor's and supplier's responsibilities in regard to both design and construction 

Rafter Roof Planning Close-Up 

bulletLet's look more closely at roof planning by reviewing a segment, this being of a 3-car garage by a porte-cochere to the right and a large motor courtyard above, bounded by a natural stone wall.

Rafter Roof Planning Close-Up, Garage, Plan View, Scaled 

KEY:

A = guidelines between floor plans, in order to orient users in structural alignments 

B = identification of cantilever soffits and dimensional extents 

C = dimensions between roof deck - not top plate - articulations 

D = roof deck perimeter lines 

E = intersecting gable identifying gable ridge, eaves, rakes, and valleys, plus cantilevers by site and extent, slope, and flare roof folds and slope 

F = fully-walled trash enclosure as outbuilding requirement of local community code, whether roofed or not - this one's not roofed 

G = note specifying construction treatment of returns in-style and generally at variance to (unfortunately) common practice  

H = note indicating design latitude still in-process with owners regarding whether to open the two roof dormers to the interiors as clerestories 

I = roof flare fold line and slope note 

J = note of roof dormer dimensions in footprint, arch type (segmental), individuated finish clad type (standing seam copper, stating seam spreads), major and minor arch axes, objective for slope 

K = dimensions from roof deck termini to dormer centerlines 

L = garage vehicle overhead door outlines 

M = slope rate and direction with note that such is typical unless otherwise identified, e.g., as in dormer identification (above)

N = attic scuttle hole access dimensions and approximate site 

O = ridge lines 

P = outside edge of top plate line 

S = roof dormer overhang  

bulletNow, let's look at roof planning it is translated to the Motor Courtyard elevation . . . 

Rafter Roof Planning Highlighted in Elevation, Garage, Facing from Motor Courtyard, Scaled 

  

Roof Planning Highlighted in Elevation, Garage, Facing Obverse of Previous, Scaled  

 

bulletNote well that in these last two pics, the letter symbols are the same as in the roof planning; see how many correlate   

KEY:

B = roof cantilever and extent 

G = note specifying construction treatment of returns in-style and generally at variance to (unfortunately) common practice  

H = note indicating design latitude still in-process with owners regarding whether to open the two roof dormers to the interiors as clerestories 

I = roof flare fold line, slope 

J = roof dormer arch per roof planning metrics note 

K2 = cross-check on roof dormer placement by centerlining to Garage vehicle door parting walls 

M = roof slope 

O = ridge lines 

P = outside edge of top plate line 

R = roof rake and raking cornice trim notes 

S = roof dormer overhang per roof planning metric 

T = cross-reference to detail of return 

bulletRafter roof planning is based atop the top plates on which the roof rests whether sawn or trussed
bulletIn a single-story home, that'd be the wall's top plates
bulletIn a two-plus story house that'd usually be the uppermost floor's wall's top plates
bulletIn a story-and-a-half, that'd usually be the first floor's wall's top plates 
 
bulletRafter roof planning is essential to developing a
bulletWatershed Plan
bulletElevations (exterior)
bulletWhole-House Section(s)
bulletRoof Overlay 
 
bulletRafter roof planning shall include overlays, in order to give residential contractors and engineers a head start in reckoning load paths and bearings 

Rafter Roof Planning, Plan View, Overlays, Scaled 

bulletWhere rafter roof planning fails
bulletCommonly, Before The Architect discovers stock plans with a roof planning sheet, if at all, then often inaccurate
bulletDrawn and texted slopes can be in conflict
bulletOvershadowed roof profiles in elevation are not left behind, but brought forward
bulletRoof layouts, particularly in elevations, suffer from the same laxity of exactitude that many elevation occasion generally
bulletDimensions are forced
bulletDimensions are locked and then the underlying layout changes without commensurate change in dimension
bulletDifficult relationships, notably in this designer's experience in regard to rafter and truss rests, are
bulletUnnoted
bulletIncorrectly noted
bulletRoof planes that are never, ever going
bulletTo intersect fully
bulletTo intersect where they're supposed to
bulletTo intersect at all 

Comment:  An unpleasant consequence of poorly defined, complex roof structures arises when Before The Architect, in consort with clients, alters perimeter lines and a proportionally similar appearance of the roof in elevation is still desirable. 

bulletThe worst roof planning in a stock plans gave rise to this study, the point of which was to convey the intricacy and interrelationships of 4 different roof structure rests two at Front Of House, two at Back Of House that, in the original, were totally blown 

Primary and Secondary Roof, Section in Elevation, Scaled  

bulletIt might be instructive to review just how much prescript and prescript needed, in this dream home designer's opinion, to communicate design and construction targets to the guys who'd ultimately be designing and constructing 

Guideline Text Accompanying Immediately Previous Section in Elevation

DATA ARE APPROXIMATE AND SHALL BE CONFIRMED AS ACCURATE OR REVISED BY OTHERS, INCLUDING BUT NOT LIMITED TO GENERAL CONTRACTOR, FRAMING CREW, AND ROOF TRUSS ENGINEERS BEFORE EXCAVATION. 

OBJECTIVES:

1. DETERMINE KNEE WALL HEIGHTS TO ROOF SEAT, IN ORDER TO HIT PEAK TARGETS OF OLD HORIZONTAL METRICS AND NEW VERTICAL METRIC WHILE KEEPING KNEE WALLS BELOW PORCHES' OVERRUNS USING ORIGINAL SLOPES AND TOP PLATE HEIGHTS.

2. PROVIDE A BASIS OF SHARED UNDERSTANDING OF THE DESIGN ESSENTIALS TO PRIMARY AND ABUTTING SECONDARY ROOF STRUCTURES OF THEMSELVES AS REPRESENTED IN ELEVATIONS AND ROOF PLANS AND AS A BASE POINT FOR POSSIBLE REVISIONS DONE BY OTHERS, E.G., ALTERED HEEL HEIGHT FROM 7 1/2LI AS-DRAWN. 

COMMENT:  THIS DESIGNER WENT TO THESE ANALYTICAL LENGTHS EVENTUALLY - AMONG OTHERS PRECEDENT - IN ATTEMPTING TO REDESIGN THE ORIGINAL FOH APPEARANCE SUBSEQUENT, NOTABLY, TO REDESIGNED EXTENSIONS OF THE GARAGE WING OUTWARDS, FIRMLY HOLDING TO AN 18LI OUTSET OF ROOF PRM TO PLATE PRM AND A 7 1/2LI HEEL, RELIANCE ON A CANTILEVER ROOF STRUCTURE FOR ALL MAJOR PLANES AT THE PERIMETER, AND A REVIEW OF ORIGINAL ROOF PLANNING MATERIAL WHICH WAS, IN THIS DESIGNER'S OPINION, UNHELPFUL OVERALL.  IN OTHER WORDS, THE HOME GOT WIDER, MAKING THE SECONDARY CROSSING RIDGE, AND, DERIVATIVELY, THE PRIMARY RIDGE HIGHER.  REGULARIZING SOFFIT STRUCTURE AND HEELS, TAKEN TOGETHER, FURTHER RAISED THE ENTIRETY OF THE ROOF NOT QUITE 6LI.

            THE KEYS TO UNDERSTANDING THE TWO MAJOR PIECES OF THIS ROOF SYSTEM ARE THAT - A) IT RESTS AT FOH AND BOH ON PLATES EACH OF TWO DIFFERENT HEIGHTS, AT FOH IN-LINE AND AT BOH OFFSET; B) THE PRIMARY ROOF MUST PEAK AT WHATEVER THE RIDGE HEIGHT IS OF THE CROSSING SLOPE.

            THE ORIGINAL'S SLOPES ARE MAINTAINED WITH THE SEMI-EXCEPTION OF THE 12:12 HIP NOW AT BOH WHICH WAS 10:12 IN THE ORIGINAL WHEN IT WASN'T 12:12 - BOTH REFERENCED.  THE ORIGIN OF THE GARAGE-SIDE LEG OF THE FOH'S LARGER DORMER REMAINS UNCLEAR. 

bulletWhere a roof planning succeeds
bulletWhen its construct agrees with
bulletWatershed Plans
bulletElevations (exterior)
bulletWhole-House Section(s)
bulletRoof Overlays
bulletFloor Plans perimeter rests
bullet3-dimension version of the roof overall 

Rafter Roof Planning Vector to Elevation, Front Of House and Floor Plan, L1, the Last Two (Vectored) in Plan View, Scaled 

  

bulletSuch agreement arises conclusively by straight-line vectors to
bulletEaves
bulletValleys
bulletPeak
bulletRidges 

bulletAn example of roof planning a rafter roof is in the immediate pic Roof Plans Vector to Elevation, Front Of House and Floor Plan, L1, relating

bulletThree sheets
bulletElevation, Front Of House (top)
bulletFloor Plan, L1 Text Version (middle)
bulletRoof Plans (bottom)
 
bulletTwo ways
bulletTop plate articulations, red
bulletRoof ridges and peaks, green 

Comment:  Please note that all three sheets are not to be published in the same scale; the Elevation will go 1/4 linear inch:1 linear foot, while the other two will be plotted at 3/16 linear inch:1 linear foot.  They're all three drawn in 1/4 linear inch:1 linear foot, but framed differently, in order to plot similarly on ARCH D (36 linear inch x 24 linear inch) in landscape.  

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