I have a King Sized Iron bed, which consists of two metal L-shaped rails running down the sides, each roughly 1 inch wide, which came with several wooden slats to rest between them.

The mattress I bought was a pocket-sprung mattress (to avoid back problems from an old, spring one). This means direct pressure on the mattress passes through to the slat(s) directly below (rather than spreading out my weight across the slats). So if myself and my partner lean too heavily on the same slat(s) they bend too much and “pop” through the frame. This happens far too easily and too often, just turning onto my side must be done with care !

This has been getting worse over time. Could this be because I need to buy new slats ? Or can I get more solid slats ? I have been to a lumber merchant to ask about “a more sturdy, denser” type of wood, but they looked at me as if I was mad ! Basically I need wood slat that can support two people across the 6 foot width of my bed.
Please help me get more sleep !