Some suppliers who offer 7mm and 9mm capping fascia boards suggest they can be used for fully replacing the fascia, however at C & A we advise that these thin fascia’s should exclusively be used for capping over existing wooden fascia. Due to the thinness, capping fascia boards may bow and bend if fixed directly to the roof rafters, so we always advise using 16mm or 18mm fascia boards in this circumstance, i.e. for new-builds or for full replacements.