C16 Span Tables - Timber Knowledge Sheet - Domestic Joists

Oct 13, 2026

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C16 Span Tables provide guidance for sizing C16 strength class solid softwood timber members for common domestic applications, including maximum clear spans and joist spacing under specified imposed and dead loads. The tables set limits for ceiling joists and flat roof joists, emphasizing kiln-dried softwood stamped to meet Eurocode 5. Naturally durable or pressure-treated timber is specified when needed for service class and lifespan. Calculations do not apply to hardwoods or engineered timber products; Eurocode 5 span tables must be consulted.

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C16 Span Tables

Purpose and scope

C16 Span Table - Domestic Ceiling Joists

C16 Span Table - Domestic Flat Roof Joists

Design D.100.01-01 | Date Published
1 July 2023 | | --- | | Document Type
Timber Knowledge Sheet | | Category Design | | Audience Architect | Designer | Engineer | Specifier | | Theme
Span Tables | | Author
Bartosz Belch for TDUK | KNOWLEDGE LIBRARY C16 Span Tables Span tables determine the size of a timber member of a particular strength class needed for a given span, plus the maximum spacing between each timber member or section. | | KNOWLEDGE LIBRARY / C16 SPAN TABLES | | | | | | | --- | --- | --- | --- | --- | --- | --- | | | Date Published Document Type Category Audience Architect | Theme Author | | | | | | | | 1 July 2023 | Timber Knowledge Sheet | Design | Designer | Engineer | Specifier Span Tables | Bartosz Belch for TDUK | | C16 Span Tables The following span tables indicate the required size of C16 strength class timber members for common uses. The following tables are solely for guidance on the loadbearing capacity of solid softwood timber members to give adequate support to floors, ceilings, and roofs in domestic dwellings. Use kiln-dried softwood in the appropriate strength class, grade stamped to comply with Eurocode 5. Naturally durable or pressure treated timber should be specified where necessary to meet the requirements of the application service class and desired service life. The calculations cannot be adapted for hardwoods or engineered timber products. Always consult Eurocode 5 Span Tables when calculating spans. In preparing these tables, Timber Development UK has assumed the complete design and build will be delivered by competent people and that thorough engineering calculations will be undertaken to verify the guidance provided in the span tables for each specific circumstance. [www.timberdevelopment.uk](www.timberdevelopment.uk) 2 | | KNOWLEDGE LIBRARY / C16 SPAN TABLES | | | | | | | --- | --- | --- | --- | --- | --- | --- | | | Date Published Document Type Category Audience Architect | Theme Author | | | | | | | | 1 July 2023 | Timber Knowledge Sheet | Design | Designer | Engineer | Specifier Span Tables | Bartosz Belch for TDUK | | C16 Span Table-Domestic Ceiling Joists Imposed load not exceeding qk = 0.25 kN/m2 and Qk = 0.9 kN. | C16 | Dead load Gk per square metre excluding weight of joist | | | | | | | --- | --- | --- | --- | --- | --- | --- | | | Gk not more than 0.25 kN/m2 | | | Gk not more than 0.5 kN/m2 | | | | | Centre-to-centre spacing of joists | | | | | | | Joist size
(breadth x depth) | 400 mm | 450 mm | 600 mm | 400 mm | 450 mm | 600 mm | | | Maximum clear span in metres | | | | | | | | | | | | | | | 38 x 89 mm | 1.50 | 1.49 | 1.44 | 1.43 | 1.41 | 1.35 | | 38 x 140 mm | 2.74 | 2.70 | 2.58 | 2.55 | 2.50 | 2.37 | | 38 x 184 mm | 3.86 | 3.78 | 3.59 | 3.55 | 3.47 | 3.27 | | 38 x 235 mm | 5.16 | 5.06 | 4.78 | 4.72 | 4.60 | 4.31 | | | | | | | | | | 45 x 95 mm | 1.78 | 1.76 | 1.69 | 1.68 | 1.65 | 1.58 | | 45 x 120 mm | 2.42 | 2.38 | 2.29 | 2.26 | 2.22 | 2.11 | | 45 x 145 mm | 3.08 | 3.03 | 2.89 | 2.86 | 2.80 | 2.65 | | 45 x 170 mm | 3.75 | 3.68 | 3.50 | 3.46 | 3.38 | 3.19 | | 45 x 195 mm | 4.42 | 4.33 | 4.11 | 4.06 | 3.97 | 3.73 | | 45 x 220 mm | 5.09 | 4.99 | 4.72 | 4.67 | 4.55 | 4.27 | | | | | | | | | | 72 x 120 mm | 2.95 | 2.90 | 2.77 | 2.75 | 2.69 | 2.55 | | 72 x 145 mm | 3.72 | 3.65 | 3.48 | 3.44 | 3.37 | 3.18 | | 72 x 170 mm | 4.49 | 4.40 | 4.18 | 4.14 | 4.04 | 3.80 | | 72 x 195 mm | 5.26 | 5.15 | 4.88 | 4.83 | 4.71 | 4.43 | | 72 x 220 mm | 6.02 | 5.90 | 5.58 | 5.51 | 5.38 | 5.05 | | | | | | | | | | 89 x 184 mm | 5.30 | 5.20 | 4.93 | 4.87 | 4.76 | 4.48 | | 89 x 235 mm | 6.93 | 6.79 | 6.43 | 6.35 | 6.20 | 5.82 | | | | | | | | | The above table provides a general summary of common permissible clear spans of simply supported domestic ceiling joists of solid timber for specified loadings, sizes and spacings. The table is solely for guidance on the loadbearing capac

FAQs

What do the C16 span tables determine for timber members?

They determine the required size of a C16 strength class timber member for a given span and the maximum spacing between members or sections.

Which timber materials do these tables apply to?

They apply to solid softwood timber members in the stated strength class. They cannot be adapted for hardwoods or engineered timber products.

What design standard should be consulted when calculating spans?

Always consult Eurocode 5 Span Tables when calculating spans.

Oct 13, 2026

Upload by ahduag