Best bathroom materials for unheated cottages
Assuming that you’ll be conscientious about draining the water system and putting an eco-friendly plumbing antifreeze in traps and toilet bowls while closing up, fibreglass and acrylic materials can be used in an unheated cottage.
There are reasons for choosing one material over another. Acrylic shower stalls and tubs are the most durable and the easiest to maintain, because they’re actually a combination of materials. A sheet of acrylic is shaped on a form and becomes the smooth, hard surface you see and feel, while the backside is reinforced and typically finished with sprayed-on fibreglass for added stability.
Less-expensive fibreglass showers and tubs are made the same way as fibreglass boat hulls: A gelcoat is sprayed into a mould, followed by the fibreglass and resins that create the rigid structure. There’s no reason these should crack if they’re correctly supported when they’re installed, but the gelcoat is a lot more fragile than the acrylic surface and will accumulate scratches in the same way your boat does.
As for toilets, if you’re installing a conventional flush toilet, the options are simple: vitreous china or lower-quality clay. Again, freezing and thawing is not the issue; durability and ease of maintenance are, and china tops clay in both.
Whether bathroom fittings will withstand winter temperatures or not really depends on the stability of the building they’re in. A proper, frost-proof cottage foundation is essential.