Insulated timber playhouse floor question

[angelboy]

I'm building the kids a playhouse and I want to make it as useable as possible all year round so it's going to be insulated and eventually have power running to it.

The structure is 3.6m x 2.4m so about the size of a decent shed and I'm going to bed nine concrete blocks into the ground and build two brick courses on top to keep the deck off the ground. I'm using 150x47mm joists with an 18mm T&G MR chipboard floor, insulation between the joists and then the plan was to clad the underside with 11mm OSB.

Does that sound OK?

I've only ever built off concrete before not a floating deck so any advice would be appreciated.

 

[RobinBHM]

I would suggest pinning tile batten 38 x 19 to the joists for the insulation to sit on. Make the insulation flush to the top and tape each joint -if using celetex. If using loft insulation I think people often use netting to support the insulation.

I think leaving the joists open to the underside allows air flow around them and will minimise the risk of rotting. I might be wrong though!

 

[angelboy]

I would suggest pinning tile batten 38 x 19 to the joists for the insulation to sit on. Make the insulation flush to the top and tape each joint -if using celetex. If using loft insulation I think people often use netting to support the insulation.

I think leaving the joists open to the underside allows air flow around them and will minimise the risk of rotting. I might be wrong though!

Yes it's plain old loft insulation. I bought 50 rolls when they were doing them at £1 per roll - They're £20/30 a roll now!

I did see someone using netting but also a recent WIP where breather membrane was used, mainly to keep rodents out. I just assumed that some solid OSB sheets would last longer than the membrane and be more protective than getting chewed through by rodents.

 

[angelboy]

Any other advice?

 

[the_g_ster]

I think this is a question on how long you want it to last.

The optimal solution would be as suggested, celotex down, and joists exposed for airflow, no risk of nesting options for bugs/mice/wasps etc in the floor.

The alternative as you suggest, is to clad the floor, to essentially make a DIY SIPP.

The risk of cladding the bottom is that condensate in the enclosed space, and in turn the rot that could start to happen.

If it isn't tanalised, I would treat with wood preserver, and then maybe get a small amount of rodent mesh in each end of the panels somehow to get cross flow of air.

In reality, a bit of wood treatment and making sure there are no holes for bugs and mice, and I am sure you will find the kids will be onto PS4's and Facebook quicker than the floor will give you an issue.

 

[angelboy]

I saw a detail of a garden room sip flooring panel here - http://www.bridgegardenrooms.co.uk/gard ... ifications which is pretty close to what I was going to build. However, it says there's a water proof membrane (so a DPM) between the concrete piles and the underneath of the flooring but the diagram shows it resting on the ground rather then being fixed to the underside of the OSB. What's the point of that if theres a gap (in my case 150mm underneath) for airflow?

 

[angelboy]

How about this - pretty good diagrams really for different construction method - https://www.gardenofficeguide.co.uk/gar ... structure/

The floor seems to have the OSB underneath but in-between the joist holding the insulation which has another OSB deck then the actual floor finishing. There's no airflow within the 'panel' but there's airflow underneath the panel, wheres the wall and roof claddings are different.