How to Build with CLT

Cross lam­i­nated tim­ber is an in­no­va­tive build ma­te­rial that can produce air­tight, well-in­su­lated homes that can be erected and made weath­er­tight in days. So why, asks Al­lan Cor­field, aren’t more UK self-builders us­ing it?

Homebuilding & Renovating - - Project Advice -

Cross lam­i­nated tim­ber, com­monly known as CLT or cross­lam, is a pre­ci­sion en­gi­neered build­ing ma­te­rial that, de­spite a raft of prac­ti­cal and eco­log­i­cal ben­e­fits, is yet to be widely adopted by the UK self-build mar­ket. Growth has, how­ever, been strong in the com­mer­cial sec­tor, and it is likely that you have seen a build­ing that fea­tures CLT: many mod­ern schools, su­per­mar­kets, gal­leries and res­i­den­tial blocks use CLT for the su­per­struc­ture. De­vel­op­ers here recog­nise CLT’S weight-to-strength ra­tio, low car­bon foot­print, speed and ease of con­struc­tion — all fea­tures that should ap­peal to the self-builder, yet take up in the res­i­den­tial mar­ket has been com­pa­ra­bly slow. How­ever, there have been a num­ber of award-win­ning self-builds in the UK fea­tur­ing CLT — in­clud­ing Adam Knibb Ar­chi­tects’ Hur­dle House, which won Best Con­tem­po­rary Ren­o­va­tion/ Ex­ten­sion in The Daily Tele­graph Home­build­ing & Ren­o­vat­ing Awards 2017, and the RIBA Award-win­ning Strange House ( be­low).

What is CLT?

The idea of stack­ing tim­ber planks (known as lamel­las) to­gether to cre­ate a con­struc­tion sys­tem can be traced back to Ger­man en­gi­neer Julius Nat­terer. He de­vel­oped a sys­tem known as Brettstapel, which orig­i­nally used nails to se­cure the wood in place (and now uses wooden dow­els). This is still widely used in Aus­tria and Ger­many and can be seen as a pre­cur­sor to CLT, which de­vel­oped out of aca­demic and in­dus­trial ef­forts in the 1990s. It dif­fers from Brettstapel in that it uses high grade tim­ber stacked in a cross pat­tern to pro­vide struc­tural strength across two axis, rather than stack­ing in a sin­gle di­rec­tion. CLT is formed of kiln-dried spruce or pine boards which are laid on top of each other at 90° (three, five, seven or nine layers de­pend­ing on struc­tural re­quire­ments), coated with a layer of polyurethane ad­he­sive and sub­jected to im­mense hy­draulic pres­sure to cre­ate large, stiff, di­men­sion­ally sta­ble pan­els.

A So­lu­tion for a Tight Site This award-win­ning 75m2 self-build, de­signed by the ar­chi­tect/owner Hugh Strange of Strange Ar­chi­tects for a tight Lon­don plot, was built us­ing CLT. The pan­els, from Eur­ban, have been ex­posed in­ter­nally and given a white­wash fin­ish.

Al­lan runs Al­lan Cor­field Ar­chi­tects, which he set up in 2009. He is an expert in de­sign­ing high-per­form­ing, en­ergy-ef­fi­cient homes. Al­lan Cor­field

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