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Timber trimmers

Sizes and details for trimming around openings

1. Permissible clear spans of trimmer beams supporting trimmed floor joists and non-load-bearing lightweight partitions (SC3 grade timber)

1 metre
loaded length
x clear span
in metres
2 metres
loaded length
x clear span
in metres
3 metres
loaded length
x clear span
in metres
4 metres
loaded length
x clear span
in metres
5 metres
loaded length
x clear span
in metres
6 metres
loaded length
x clear span
in metres
Size in mm
for 2 trimmer beams
2.36 1.91 1.58 1.35 1.15 0.87 38 x 147
2.75 2.22 1.85 1.59 1.41 1.11 38 x 170
3.16 2.56 2.14 1.85 1.64 1.37 38 x 195
3.58 2.90 2.42 2.11 1.88 1.63 38 x 220
2.55 2.14 1.78 1.54 1.36 1.23 47 x 147
2.96 2.50 2.09 1.81 1.61 1.45 47 x 170
3.41 2.88 2.41 2.10 1.87 1.69 47 x 195
3.85 3.25 2.73 2.38 2.13 1.93 47 x 220
2.83 2.39 2.11 1.83 1.63 1.48 63 x 147
3.28 2.78 2.46 2.14 1.91 1.73 63 x 170
3.76 3.20 2.83 2.47 2.21 2.01 63 x 195
4.25 3.63 3.20 2.80 2.51 2.29 63 x 220
3.00 2.54 2.26 2.03 1.81 1.64 75 x 147
3.47 2.96 2.64 2.36 2.11 1.92 75 x 170
3.99 3.41 3.04 2.73 2.44 2.23 75 x 195
4.50 3.85 3.45 3.08 2.77 2.53 75 x 220

Figure 1

Double trimmer beam bolted together

Detail

Proprietary joist hanger to suit joist width and loading

Proprietary joist hanger to suit joist width and loading.

Notes:

  1. Bolt trimmer using 51mm diameter double sided round tooth plate connectors and M12, grade 4.6 bolts at 600mm centres
  2. Maximum partition load 0.8kn/m (for example: timber stud partition clad with 9.5mm or 12.5mm plasterboard)
  3. Notches are not permitted in the trimmer beam.

2. Permissible clear spans for trimmer joists supporting trimmer beam and non load-bearing lightweight partitions (SC3 grade timber)

See figure 2 for positions A, B, C and S

Trimmer size (mm) For ratios of A/B up to 0.25
Dimension C (m)
1.0
Clear Span (m) S
For ratios of A/B up to 0.25
Dimension C (m)
2.0
Clear Span (m) S
For ratios of A/B up to 0.25
Dimension C (m)
3.0
Clear Span (m) S
For ratios of A/B between 0.26 and 0.49
Dimension C (m)
1.0
Clear Span (m) S
For ratios of A/B between 0.26 and 0.49
Dimension C (m)
2.0
Clear Span (m) S
For ratios of A/B between 0.26 and 0.49
Dimension C (m)
3.0
Clear Span (m) S
For ratios of A/B between 0.5 and 0.74
Dimension C (m)
1.0
Clear Span (m) S
For ratios of A/B between 0.5 and 0.74
Dimension C (m)
2.0
Clear Span (m) S
For ratios of A/B between 0.5 and 0.74
Dimension C (m)
3.0
Clear Span (m) S
2 Number x 38 x 147 3.02 2.77 2.56 2.55 2.19 1.87 2.45 2.10 1.83
2 Number x 38 x 170 3.51 3.23 3.01 2.97 2.55 2.19 2.84 2.44 2.13
2 Number x 38 x 195 4.03 3.73 3.49 3.42 2.95 2.55 3.26 2.81 2.46
2 Number x 38 x 220 4.55 4.23 3.97 3.87 3.34 2.90 3.69 3.17 2.79
2 Number x 47 x 147 3.25 2.98 2.77 2.75 2.44 2.12 2.64 2.36 2.06
2 Number x 47 x 170 3.76 3.48 3.25 3.20 2.85 2.48 3.06 2.74 2.40
2 Number x 47 x 195 4.32 4.01 3.76 3.68 3.30 2.87 3.51 3.14 2.77
2 Number x 47 x 220 4.87 4.54 4.27 4.16 3.74 3.26 3.96 3.54 3.13
2 Number x 63 x 147 3.58 3.30 3.08 3.05 2.72 2.48 2.91 2.66 2.43
2 Number x 63 x 170 4.14 3.84 3.60 3.53 3.17 2.90 3.37 3.09 2.82
2 Number x 63 x 195 4.73 4.42 4.16 4.06 3.66 3.36 3.87 3.55 3.24
2 Number x 63 x 220 5.43 5.00 4.72 4.58 4.14 3.82 4.36 4.02 3.65
2 Number x 75 x 147 3.78 3.50 3.28 3.23 2.89 2.65 3.09 2.82 2.62
2 Number x 75 x 170 4.37 4.07 3.82 3.74 3.37 3.09 3.57 3.28 3.05
2 Number x 75 x 195 5.00 4.68 4.41 4.30 3.88 3.58 4.10 3.77 3.52
2 Number x 75 x 220 5.62 5.28 4.99 4.84 4.39 4.06 4.62 4.26 3.98

Figure 2

Trimmed joists

Detail

Proprietary joist hanger to suit joist width and loading

Detail of propriety joist hanger to suit joist width and loading.

Notes

  1. Bolt trimmer using 51mm diameter double sided round toothed plate connectors and M12 grade 4.6 bolts at 600mm centres
  2. Maximum partition load 0.8kn/m (for example: timber stud partition clad with 9.5mm or 12.5mm plasterboard)
  3. Notches are not permitted in the trimmer beam