roof construction

Level 1 Diploma in Carpentry and Joinery

1

Construction of Roofs

6.1 – 6.5

Unit 101/501: Principles of building construction, information and communication


2

Objectives

To be able to:

6.1 Identify types of roofs

6.2 Identify components of roofs

6.3 State paint systems for timber

6.5 State the importance of thermal insulation in a roof


3

Lean-to Roof


4

Mono Pitch


5

(Double) Pitched Roof


6

Pitched Roof, Gable End

CROSSGABLE

RIDGE

VALLEY

EAVES

GABLEEND


7

Pitched Roof, Hipped End


8

Flat Roof


9

Flat Roof Fall

A flat roof is normally used on garages or small extensions. It is much less commonly used as the main building’s roof.

The direction of the slope of a roof is called the fall.

Flat roofs are not actually flat: a flat roof is any roof which has a slope of up to 10 degrees : a fall ratio of 1:6.

The amount of fall should be enough to clear away any water and direct it to the guttering.

If the fall is not enough, the water will form pools on top of the roof.


10

Sloping Roof Joists are used where there is no level ceiling required below:

Tapered Firring Pieces are attached to the roof joists, producing a level ceiling:

Deepened joists uses parallel firring pieces, at diminishing sections, nailed at right angles to the fall of the roof:

Obtaining the Fall on a flat roof


11

Components of a flat roof


12

A pitched roof can be a single roof or a double roof.

A double roof with a larger span requires support for the rafters, which are called purlins.

Single and Double Roofs

Single roof Double roof


13

Components of Roofs

Most roofs are constructed in one of two ways:

Modern (prefabricated) roof trusses Traditional cut roof


14

King Post Truss

Fan Truss Attic (room in the roof) Truss

W (fink) Truss

Common Truss Profiles


15

Roof Components: Traditional Cut Roof

Common Rafter Ridge(board)

Collar Tie

Purlin

StrutStrut Ceiling Joist

Wall (top) Plate

Strutting Beam

Apex (the highest point)


16

Roof Components: Under the Eaves

• Eaves: the overhanging lower edge of a roof

• Soffit: the underside of an overhanging roof eave

• Fascia: runs along the lower edge of the roof


17

Paint Systems for timbers

It is important to use only paint systems which meet with the given specification and current legislation so as to comply with COSHH and the HASAWA.

The most common paint system for timber is primer-undercoat-gloss:

• Primer adheres to the timber surface (without it, subsequent coats would flake straight off).

• Undercoat is the coating which follows the primer in order to build the thickness of the paint film: to give opacity, to fill very minor depressions and gaps, to provide a suitable ground in

readiness for the finishing coat.

• Gloss the finishing coat(s), providing a durable surface that can be wiped clean and (depending on type) resistance to weathering.


18

The importance of Thermal Insulation in a roof

• Energy is expensive.

• When thermal insulation is used in a building, less power is required to keep the building warm in Winter and cool in Summer.

• The better the insulation, the cheaper it will be to inhabit the building.

• Around one quarter of building heat loss is through the roof space.

• Thermal insulation in a roof will make a dramatic difference to the cost of inhabiting the building.

roof construction

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