Building science wood

1. Dr f Dejahang (BSc CEng, BSc (Hons) Construction Mgmt, MSc, MCIOB,
PhD)
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LESSONS
Dr f Dejahang BSc CEng, BS (Hons) Construction Mgmt, MSc, PhD

4. WOOD
 The Mechanical properties and availability of
wood have made it a natural material for:
 building structures
 Furniture
 Tools
 Vehicles
 decorative objects
 Etc

5.  Worldwide it is used more than metal or
plastic.
 Wood is a natural product and when used
responsibly is a sustainable resource which
need not result in damage to the
environment.
 Forests can be protected by recycling and
reusing the wood, using less wood and by
supporting sustainable forest management

6.  The strength of wood is highly dependent
on the loading direction.
 Wood is strongest in tension along the
fibres and is weakest in the radial and
tangential direction.
 When loaded in its strongest direction
(longitudinal along the grain - wood can
have a strength to weight ratio advantage
relative to steel of 2:1.

7.  When wood is loaded in other directions (radial
and tangential to the grain this advantage
disappears.
Wood Types
 It is customary to describe wood using the
following terms.
 there is some degree of overlapping in practice.
 Carpentry- applying to structural work in buildings
and ships

8.  Timbering - applying to temporary
work such as formwork for concrete,
gantries and shoring
 Joinery -wooden structures inside
buildings, such as doors and window
frames
 Cabinetwork - cabinetry - making
furniture

9. Hardwoods
 Hardwood trees are generally broadleaved
trees.
 These tree species are deciduous, retaining
their leaves only one growing season.
 The designation Hardwood trees does not
necessarily relate to the hardness of the wood.
 Hardwood trees are also called broad leaf trees
or deciduous trees.

10. Typical hardwood trees include:
 Ash
 Elms
 Oak
 Maple
 Walnut
 Hickory
 mahogany, and walnut.

11. Woods grown in tropical
climates are generally
hardwoods.
Hardwood have shorter fibres’
compared to softwood.
Some hardwoods are
evergreen.

12. Softwoods
 Softwoods are one of the botanical groups
of trees that have persistent needle-like or
scale-like leaves;
 softwoods are evergreen and have longer-
length fibres’ than hardwoods.
Softwood trees include pines, spruces,
firs, cedars.

13.  The yew is one of the few types of
softwood that is native to the UK.
 There are a number of softwoods
(yew) that are harder and tougher
than many hardwoods
Larches, including tamarack, are
exceptions, being deciduous
"softwoods".

14. Use of timber in
construction
 Today, when architects and engineers
design landmark buildings like bridges or
government offices, schools or Factories,
they look to timber to express a
contemporary beauty which is nonetheless
rooted in nature and a respect for the
environment.

15.  The flexibility of lightweight modular timber
construction is particularly suited to multi-purpose
halls because of its ready adaptability.
 Wood is a high-performance material
 low in weight
 high in density, with excellent load-bearing and
thermal properties
 and the availability of a wide range of timbers,
each with its own characteristics, means wood
can be suitable for most special requirements.

16. One specific advantage of wood
is its ability to reduce energy
use.
Timber construction has a
higher heat insulation value
than conventional construction
methods, even with lower wall
thicknesses.

17.  An external wall constructed using
timber may have only half the
thickness of a brick or concrete wall
 yet provide double the thermal
insulation value
 while at the same time avoiding the
thermal bridging common with other
construction methods.

18. Flexibility
 The flexibility of timber construction methods
makes it easier to vary a building’s orientation
on site, its floor plan, the number of rooms, the
interior design and the overall appearance
 while timber’s thermal efficiency means walls
can be slimmer
 releasing up to 10% more space than other
building methods.

19. Fire prevention
 Unlike many other materials, timber behaves
predictably in fire
 forming a charred surface which provides
protection for the inner structure
 timber elements can remain intact and fully load-
bearing during a fire.
 The fire-retardant detailing of modern timber
construction prevents cavity fires and the spread
of combustion gases

20. Sound insulation
 Modern timber buildings readily
comply with sound insulation
standards through using a layered
structure of different materials.
 Even more demanding standards can
be met using a number of different
design solutions.

21. Durability
 With good design and correct detailing,
structural wood needs no chemical
treatment to achieve a long life.
 Wood is resistant to heat, frost, corrosion
and pollution;
 the only factor that needs to be controlled
is moisture

22.  Wood is a unique and renewable material
 As trees grow they naturally absorb CO2
from the atmosphere
 Wood is the building material of the
future
 The materials used in a typical 2-
bedroomed semi-detached house in
England emit about 14 tonnes of CO 2 in
their extraction and manufacture.

23.  By using timber frame, you can save
up to 9 tonnes per house;
 by increasing the amount of wood
products such as:
 wood windows,
 doors
 Flooring
 They saves still more CO 2
 Recycling and re-use of wood

24. Reconstituted wood-based products

25.  Similarities and differences between steel and
timber as structural materials.