Solid Timber Roof Decking

   


Portsmouth Grammer School showing construction

Solid timber roof decking is supplied in four depths with ex. 38mm and 50mm
deep boards having a single T. G. and rebated section and ex. 63mm and
75mm a double T. G. and rebated section. This provides for the appropriate
depth to be chosen from the table below to span up to 6.3m between beam
centres. With the boards stitched nailed to each other and nail fixed to the
laminated timber beams the finished deck is therefore a very strong membrane
which can be used to provide a useful shear diaphragm.

The decking is produced from SS grade North European Whitewood and is
finger jointed to lengths that ensure that butt joints occur over beams. In most
cases it is pressure impregnated with a solvent or water-borne preservative.


The natural appearance of solid timber decking exposed as a finished ceiling
used together with glulam is warm and very pleasing. Timber decking also has
the advantages of being easy to fix to, of having good insulation properties and
of providing and economic alternative to traditional constructions.
   
   
   
   



Dimensions of Solid Timber Decking

DEPTH
BREADTH
NOMINAL
ACTUAL
NOMINAL
COVER
38
50
63
75
34
45
58
70
150
150
150
150
135
135
135
135




Span Tabels for Solid SS Grade Timber Decking

Total
Distributed
Load
SINGLE SPAN
DOUBLE SPAN
ALTERNATE SINGLE
& DOUBLE SPAN
Spans in metres for
nominal depth
Spans in metres for
nominal depth
Spans in metres for
nominal depth
kN/m2
38 mm
50 mm
63 mm
75 mm
38 mm
50 mm
63 mm
75 mm
38 mm
50 mm
63 mm
75 mm
1.00
1.25
1.50
1.75
2.00
2.25
2.50
2.75
3.00
2.2
2.1
1.9
1.8
1.7
1.6
1.6
1.5
1.5
3.0
2.7
2.6
2.5
2.3
2.2
2.2
2.1
2.1
3.8
3.5
3.3
3.2
3.0
2.9
2.8
2.7
2.6
4.7
4.3
4.0
3.8
3.6
3.5
3.4
3.3
3.2
3.0
2.8
2.6
2.5
2.4
2.3
2.2
2.1
2.1
3.9
3.7
3.4
3.3
3.1
3.0
2.9
2.8
2.7
5.2
4.8
4.5
4.3
4.0
3.9
3.7
3.6
3.5
6.3
5.8
5.4
5.2
4.9
4.8
4.6
4.5
4.3
2.5
2.3
2.2
2.1
1.9
1.8
1.8
1.7
1.7
3.3
3.1
2.9
2.7
2.6
2.5
2.5
2.4
2.3
4.3
3.9
3.7
3.5
3.4
3.2
3.1
3.0
3.0
5.2
4.9
4.6
4.3
4.2
3.9
3.8
3.7
3.6






Decking Profiles.
The design of the decking is limited to a
deflection of span/240 using the permitted
grade value of elasticity of 10500 N/mm2 and
considering a bending stress of 7.5 N/mm2
(BS 5268 recommends deflection limited to
span/333 but this is to limit the cracking of plaster ceilings - which would not be used with decking).