{"id":1306,"date":"2017-09-08T10:08:42","date_gmt":"2017-09-08T10:08:42","guid":{"rendered":"http:\/\/blogs.napier.ac.uk\/cwst\/?p=1306"},"modified":"2019-11-17T23:03:28","modified_gmt":"2019-11-17T23:03:28","slug":"c-d-stand","status":"publish","type":"post","link":"https:\/\/blogs.napier.ac.uk\/cwst\/c-d-stand\/","title":{"rendered":"C and D &#8211; what do they stand for?"},"content":{"rendered":"<p>The European Standard EN 338 contains a list of strength classes for structural timber. \u00a0There is a set primarily for softwoods which begin with the letter C (e.g. C16 and C24) and a set for hardwoods which begin with the letter D (e.g.D24 and D30).<\/p>\n<p>It is sometimes said (e.g.\u00a0<a href=\"http:\/\/www.cti-timber.org\/sites\/default\/files\/STA_Timber_as_structural_material.pdf\" target=\"_blank\" rel=\"noopener noreferrer\">1<\/a>, <a href=\"http:\/\/webarchive.nationalarchives.gov.uk\/20120919151528\/http:\/\/www.communities.gov.uk\/documents\/planningandbuilding\/pdf\/Structuraleurocodebd2405.pdf\" target=\"_blank\" rel=\"noopener noreferrer\">2<\/a>, <a href=\"https:\/\/books.google.co.uk\/books?id=jJZSS8MS1zMC\" target=\"_blank\" rel=\"noopener noreferrer\">3<\/a>) that the C stands for Coniferous and D stands for Deciduous.\u00a0 Indeed the 1995 version of EN 338:1995 even uses those words in the table header. This doesn&#8217;t really make sense.<\/p>\n<p>Firstly &#8211; the 2016 revision of EN 338 allows hardwoods to be assigned to C grades&#8230;so they are no longer exclusively for softwood. \u00a0But there is a more fundamental issue&#8230;<\/p>\n<p>Softwoods are conifers. \u00a0Conifers are gymnosperms &#8211; cone bearing seed plants.<\/p>\n<p>Hardwoods (or broadleaves) are angiosperms &#8211; flowering plants. \u00a0More particularly, they are dicotyledons (they have two seed leaves) putting them in a different category from bamboo (which is a monocotyledon, one seed leaf)<\/p>\n<p>Whereas&#8230;<\/p>\n<p>Deciduous means that the tree loses its foliage for part of the year &#8211; as opposed to evergreen, where the foliage is kept all year.<\/p>\n<p>Hardwood is not synonymous with deciduous. \u00a0\u00a0Many tropical timbers are evergreen &#8211; so it would certainly not make sense to think that the D in D70 Greenheart stands for deciduous!<\/p>\n<p>And while we are on the topic &#8211; conifer is not synonymous with evergreen either! \u00a0The most familiar deciduous conifers are larches &#8211; but there are a few others too (list below).<\/p>\n<p>So what do C and D stand for? \u00a0Well &#8211; they don&#8217;t need to stand for anything. \u00a0But if they had to &#8211; Conifer and Dicot would make slightly more sense.<\/p>\n<p>Deciduous\u00a0conifers:<\/p>\n<p>Larches, which include<br \/>\n<em>Larix decidua<\/em> (European larch) [LADC]<br \/>\n<em>Larix kaempferi<\/em> (Japanese larch) [LAKM]<br \/>\n<em>Larix x eurolepis\u00a0<\/em>(Dunkeld larch) [LAER]<br \/>\n<em>Larix occidentalis<\/em> (Western larch) [LAOC]<br \/>\n<em>Larix gmelinii<\/em> (&#8220;Siberian&#8221; \/ Dahurian larch) [LAGM]<\/p>\n<p><em>Pseudolarix amabilis<\/em> (Golden Larch)<\/p>\n<p><em> Taxodium distichum<\/em> (Southern \/ Bald cypress) [TADS]<br \/>\n<em>Taxodium ascendens<\/em> (Pond cypress)<\/p>\n<p><em>Glyptostrobus pensilis<\/em> (Chinese Swamp Cypress)<\/p>\n<p><em>Metasequoia glyptostroboides<\/em> (Dawn Redwood)<\/p>\n<p>[XXXX] is the EN 13556 species code<\/p>\n","protected":false},"excerpt":{"rendered":"<div class=\"mh-excerpt\"><p>The European Standard EN 338 contains a list of strength classes for structural timber. \u00a0There is a set primarily for softwoods which begin with the <a class=\"mh-excerpt-more\" href=\"https:\/\/blogs.napier.ac.uk\/cwst\/c-d-stand\/\" title=\"C and D &#8211; what do they stand for?\">[&#8230;]<\/a><\/p>\n<\/div>","protected":false},"author":57,"featured_media":21,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_crdt_document":"","jetpack_post_was_ever_published":false,"footnotes":""},"categories":[5,37],"tags":[68,75,81],"class_list":["post-1306","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-standards","category-thoughts","tag-en338","tag-hardwoods","tag-softwoods"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.3 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>C and D - what do they stand for? 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