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TitleTHE OPEN TIMBER CONSTRUCTION SYSTEM Architectural Design
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LanguageEnglish
File Size3.5 MB
Total Pages116
Document Text Contents
Page 1

THE OPEN TIMBER CONSTRUCTION SYSTEM

Architectural Design

Page 2

THE OPEN TIMBER CONSTRUCTION SYSTEM
Architectural Design

Page 58

57THE OPEN TIMBER CONSTRUCTION SYSTEM Architectural Design

Fire Safety

Regulations

The performance properties of building components is de-
scribed using the following symbols:
R = load-bearing capacity
E = integrity
I = insulation capacity

By combining the letters, the varying performance require-
ments set out for different building components can be dis-
closed (R, REI, EI). The required performance properties are
given specifi c performance periods, which may be any of the
following: 15, 30, 45, 60, 120, 180 or 240 minutes.

In case of fi re load-bearing and/or bracing building compo-
nents must sustain a certain load capasity, specifi c to the given
fi re resistance time of any individual building.

Compartmented areas within a building must prevent fi re
from spreading from one compartment to another for a specifi c
required period.

Material classes are symbolised by using the following: A, B,
C, D, E and F. Even though an attempt is currently being made
to unify regulations, there are still many variations between
different countries. Therefore, during the design process, at
least the following design aspects must be re-referred back to
appropriate local regulations:

Fire Category, Safety Classes or similar
- the correct fi re category of the building, according to its use

and size.
- fi re category affects the structural fi re resistance require-

ments and also all of the following, as listed below.

Fire Resistance Requirement
- in low rise buildings, i.e. for buildings of a maximum of two

storeys, the requirement concerning fi re resistance is usually
EI 30

- in taller buildings, of more than two storeys, the requirement
is usually REI 60

The maximum number of storeys
- this varies according to different countries. In some countries

a building is regulated by its height, in others by its number
of fl oors.

Possible limitations to the overall fl oor areas
- they may be based on the use of the building and on the

number of fl oors.

Compartment requirements
- in apartment blocks, individual apartments form compart-

ments
- unless regulations state otherwise, in REI 60 category

buildings the roof space must be compartmentalised us-
ing category EI 30 structures in line with compartments on
fl oors below. In EI 30 category buildings, category EI 15 is
adequate for roof spaces.

INSULATION AND SHEATHING ALTERNATIVES

Page 59

58 THE OPEN TIMBER CONSTRUCTION SYSTEM Architectural Design

Classifi cation requirements for fi nishing
materials
- usually they are determined by the building’s use and number

of fl oors
- if the external cladding is made of timber or other infl am-

mable material, in buildings that are more than two storeys
high, the breather membrane should consist of materials
that comply with Euroclasses A1 or A2.

Sprinklers
- sprinklers may alter maximum permitted fl oor areas and the

choice of materials.

Typical example structures that comply with the different
regulations are presented and illustrated at the end of
this guide. Due to the variations in calculation principles,
related to various regulatory classifi cations and categories
between different countries, the given ratings are only
indicative.

Restricting fi re from spreading along the surface
of an external wall and within ventilation cavity
Fire can be prevented from spreading along the surface of an
external wall and within a ventilation cavity by vertically com-
partmentalising the ventilation cavity at 120 cm intervals and by
limiting the cavity to extend to no more than one storey at a time.
In the area of limitation the cavity may be no more than 20% of
the free cavity. Consequently, if the cavity is compartmentalised,
the usual requirement, which states that the continuous surface
of the external cladding at each fl oor must be broken by using
fi re stops (e.g. 200 mm projections) at regular intervals, does
not apply. Local authorities must always be consulted where
the choice of design solutions concern fi re regulations.

Horizontal compartmentalising means that the ventilation
cavity is divided into vertical sections by breaking the width
of the cavity with a barrier, a thick batten or similar. This pre-
vents the fi re from spreading horizontally within the ventilation
cavity.

Limiting the ventilation cavity at each fl oor means that the
depth of the cavity is reduced, but airfl ow is not completely ob-
structed. By reducing the gap, the otherwise resultant chimney
effect within the cavity is obviated and the vertical spread of
fi re through the cavity delayed.

INSULATION AND SHEATHING ALTERNATIVES

Page 115

114 THE OPEN TIMBER CONSTRUCTION SYSTEM Architectural Design

NOTES

Page 116

Esimerkkisivu rakennetyypeistä

This guide introduces and describes
the open timber construction system.
In addition it also lists those building
regulations that affect the design and
construction of timber buildings and
presents some model structures that
comply with these regulations.

The guide is intended primarily for
the use of architects and students of
architecture or building construction.
Its aim is to demonstrate the parame-
ters and potential that the open timber
construction system provides for the
design of buildings.

The guide deals mainly with the
design of residential buildings. Howe-
ver, whenever appropriate, it can also
used as reference in the design of other
building types.

The guide is divided into the follo-
wing seven chapters:
1 THE SYSTEM
2 STRUCTURAL FRAME AND

ARCHITECTURAL DESIGN
3 INSULATION AND SHEATHING

ALTERNATIVES
4 SERVICES (HEATING,

PLUMBING, VETILATION AND
ELECTRICAL INSTALLATIONS)

5 ARCHITECTURAL AND STRUC-
TURAL REPRESENTATION

6 MODEL EXAMPLE
STRUCTURES

7 JUNCTION DETAILS

ISSN: 0789-578X
ISBN: 952-15-0184-7

THE OPEN TIMBER CONSTRUCTION SYSTEM
Architectural Design

86 THE OPEN TIMBER CONSTRUCTION SYSTEM Architectural Design

Timber roof YP1 (REI 60)

1. Roof and underlay
2. Roof truss
3. 50 mm thermal insulation, with breather membrane surface,

Euroclasses A1 or A2
4. 300 mm thermal insulation, Euroclasses A1 or A2, and 48

mm x 220 mm load-bearing ceiling joists, dimension and
spacing to be calculated for each individual project

5. Vapour barrier
6. Perpendicular battens (space for sprinkler pipes)
7. Double building board, class according local requirements.

The structure meets with thermal insulation requirement
U < 0.16 W/m2K
This solution is particularly suitable for situations where load-
bearing partitions are parallel to roof trusses.

Timber roof YP2 (REI 60)

1. Roof and underlay
2. Roof rafter, upper chord of roof truss
3. 50 mm thermal insulation, with breather membrane surface,

infl ammable or almost infl ammable
4. 300 mm thermal insulation, Euroclasses A1 or A2
5. Ceiling joist, lower chord of roof truss, with adequate provi-

sion for charring in case of fi re
6. Vapour barrier
7. Perpendicular battens (space for sprinkler pipes)
8. Single or double building board, class according local re-

quirements.

The structure meets with thermal insulation requirement
U < 0.16 W/m2K
In the solution, the lower chord of the roof truss performs as
load-bearing structure in a fi re situation.

MODEL EXAMPLE STRUCTURES

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