Floor boarding and calculations 4

City & Guilds Construction
© 2013 City and Guilds of London Institute. All rights reserved. 1 of 11
PowerPointpresentation
Floor boarding and calculations
Unit 202: Principles of building construction,
information and communication

Aims and objectives
Aim:
• Introduce learners to floor boarding and calculations.
Objectives:
• Identify components of a timber floor.
• Describe each component of a suspended timber floor.
• Calculate the linear quantity of floor boarding to cover an irregular
shaped area.
• Calculate additional quantities of wastage using percentages.

Flooring
Much of the terminology used for timber floors and for timber flat roofs
is the same, and many of the principles used in their construction are
also the same. Therefore by learning about either one, you can find out
much about the other.
A floor is defined as a level surface area within a construction suitable
for, and capable of supporting, the load it is designed to carry.
The design will depend on the type of building – eg a house for living
purposes, a factory for industrial use, a warehouse for storage use, or a
shop. The floors may be constructed from timber, concrete or other
materials, but only timber floors are dealt with in this section.

Terminology
Wall plate: Bedded on top of the support walls, and to which the joist
ends are fixed. Cross-section size usually 100mm x 50mm, but may
differ according to specification.
Wall bearer: As wall plates, but fixed to a wall face by bolts or other
means. Cross-section size as specified to the suit span of the joist.
DPC: Damp Proof Course – a brickwork material through which
moisture cannot pass.
Air brick: Honeycombed brick through which air can pass.
Joist hanger: A metal frame (or shoe) fixed into a wall (or to a
supporting joist), for supporting the end of a joist. Size to suit joist
section size.

Terminology
Strap anchor: A metal bar fixed to a joist and to a supporting wall to
prevent lateral floor/wall movement.
Bridging joist: Spanning the shortest distance from support wall to
support wall, and the support for the floor board. Cross-section size
determined by span and loading.
Trimming joist: Fixed in the same direction as a bridging joist, but at
one or both ends of an opening supporting the trimmer joist, and the
edges of the decking. Cross-section as the bridging joist but thicker, or
double joists may be used.
Trimmed joist: Fixed in the same direction as the bridging joist, but
cut (trimmed) shorter to allow for an opening to be formed in the floor.
Cross-section size the same as bridging joist.

Terminology
Trimmer joist: Fixed (usually at right-angles to the bridging joists) at
the side of an opening to support the ends of the trimmed joists, and
the edge of the decking. Cross-section as the bridging joist but thicker,
or double joists may be used.
Struts: Fixed in rows between joists and at right-angles to bridging
joists, to restrict buckling of the joists. The position and number of rows
will depend on the joist span.
Noggings: Fixed between joists to support joints in decking material
(eg floorboard trap, roof decking joints).
Decking: Sheet materials or boarding used for covering a floor or roof
surface area.

Suspended timber flooring

Calculating for sheet flooring
Flooring is calculated in m2.
• To calculate the area, the formula is length x width.
• Sheet flooring is approximately 900mm wide x 1800mm long =
approximately 1.62m2.
For example:
• If you have a room 4.3m x 6.4m, the area = 27.53m2.
• Now divide the room floor area by the sheet flooring area.
• 27.53m2 / 1.62m2 = 16.9 = 17 sheets of flooring.

Calculating for floor boards
The formula for floor boards is similar to that for sheet flooring.
Floor board widths vary depending on the supplier, but are generally
150mm wide x 5m long, which is the size we will use.
Flooring is laid across the joists (the length of the room).
If you have a room 4.3m (L) x 6.4 (W) the area = 27.53m2.
= 4.3m / 150mm = 28.6
= 28.6 x 6.4 = 183.5m
= 183.5m / 5m = 36.693 lengths of floor board
= 37 lengths of floor boards at 5m long.

Calculating for wastage
Wastage is generally calculated at 15%. This ensures that there is sufficient
flooring, as in some circumstances flooring has to be cut and wastage is
inevitable. We will calculate for the previous two flooring calculations.
Sheet flooring:
27.53m2 / 1.62m2 = 16.9 = 17 sheets of flooring
17 x 15% = 2.55 = 3 sheets
17 + 3 = 20 sheets
Floor boards:
183.5m / 5m = 36.693 = 37 lengths of floor board
37 x 15% = 5.55 = 6 lengths
37 + 6 = 43 lengths

Any questions?

Student to work on
Please go and work on activities:
11,12,13,14,14,16
And worksheet:
4

Floor boarding and calculations 4

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