Garden room floor

Morning,

Sorry if this has been posted before but I cant seem to find my exact potential problem. I am in the process of building a garden room and I'm little confused/worried about the floor I have an old concrete base in the garden already which is in great condition, dead level and sits around 30mm/50mm above a surrounding patio. Its roughly 150mm thick but has no DPM. My plan is to lay a DPM sheet over the base area of the building. Put the C24 timber floor joists on top of this then wrap the DPM 200mm or so up to the OSB3 walls which will then be cladded. The base will be slightly bigger than the building on 2 sides all water from the roof will be ran away in guttering ect so will just be a small amount on water hitting the base.

Is this a good solution or am i likely to have issues with damp rot ect? don't really want to raise it use bearers ect as I need to try and keep the height down as much as possible

any help/advice would be greatly appreciated.

I'm no expert, but was considering a similar thing to you a few weeks ago. Slight difference is that my shed is going to be on 40mm plastic bearers as the floor joists. My floor is going to be P5 chipboard, so I was worried about moisture somehow rising up to the bottom of the chipboard.

I posted a similar proposal of using DPM to protect the underside of my floor on this forum here, along with my concerns about dpm actually trapping condensation and moisture in. Someone agreed, so I changed my plan. Instead I'm going to paint bitumen paint on the bottom of my boards. Haven't done it yet, so can't say if it was a good idea. Food for thought perhaps?

BTW, I got my plastic 'joists' from a company called filcris - maybe that's also something to consider?

Thanks for the reply. Looked into a bit more am also going to use bitumen paint and make sure it's got some air flow

Thanks for the thoughts and suggestions

Jonnymm said:

Thanks for the reply. Looked into a bit more am also going to use bitumen paint and make sure it's got some air flow

Thanks for the thoughts and suggestions

Click to expand...

DPM has the risk of condensation.

When I did my garden room I used 10mm plastic spacers - just enough to keep the timber off the damp concrete.