Do I need to use treated wood to raise boards?

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I’m adding 90mm of timber across existing 170mm joists to raise loft boards so I can get 260mm of insulation under them


Do I need to use treated timber for this job or is untreated OK?

 

[Deleted member 174758]

Untreated is OK. Treated is normally used where it can be directly exposed to weather (e.g. fences), where it is going into a known damp environment (e.g. ceiling support joistsfor a lathe ceiling in a sauna) or where the timbere ds are going into masonry pockets in the external walls of buildings with solid (non-cavity) walls. And other such situations