How to build mezzanine floor for kids bedroom?

[Mich5012]

I am wanting to install a mezzanine floor in my kid's bedroom to free up some space below. She will have her bed on the mezzanine level and below will be a study/leisure area. The mezzanine size will be 2580mm x 1980mm - just enough room for a queen bed. As room ceiling height is a consideration and I want to maximise headroom on the mezzanine level, I am wanting to create the support grid with beams/joists at the minimum thickness, still allowing for safety etc. From my research I think the beams need to be 140mmx45mm, but not sure if I could use 90mmx45 instead. Any advice on either timber or steel options that minimise the thickness of the mezzanine floor. Much appreciated.

[EricL]

Hello @Mich5012

Welcome to the Bunnings Workshop community. It's fabulous to have you join us, and thank you for sharing your question about building a mezzanine floor for your kid's bedroom.

I'm afraid the 90x45 will not be strong enough to carry the extra weight placed on top. If you look at typical flooring frame plans, they often use large timber pieces like the 140x45 so that they can carry the weight placed on them and they don't need as much post support underneath. But because you are building a complex weight-bearing timber structure that needs to be very safe, I recommend engaging the services of a registered builder for this particular project. 

Another option is to create a bunk bed-type system where the study table is underneath the bed. It can still be a large bed at the top so that you can have a large study table at the bottom. If built properly it can even be used by adults.

Let me call on our experienced members @TedBear, @tom_builds, @diy_hausdesigns and @Adam_W for their recommendations.

If you have any other questions we can help with, please let us know.

Eric