Risk of moisture under the house?

[Minde Passby]

Hello!
I am in the process of building a small house (180x180) for my ducks. I have laid a foundation of Leca blocks with about 30-50 cm to the ground (there's a steep slope, clay/soil so I dug out for the blocks, see image). Inside the foundation, I have filled it up with old crushed bricks and plan to toss in some buckets of gravel as well. Bitumen felt is secured on the inner side of the floor joists and slopes out over the walls, so I'm not worried about moisture from the walls.

Now to my question:
The subfloor will consist of whatever wood I have on hand, untreated, do I risk getting moisture in the floor from the ground since I don't have any geotextile down to the soil? Should I put something in to secure the wood before laying the subfloor?

Grateful for encouragement/help.

This is how I have planned the foundation from top to bottom:

• Chipboard
• Building foil
• Insulation
• Vapor barrier
• Subfloor
• Chicken wire (tensioned as extra protection from foxes/rats)
• Air gap of about 15-30cm
• Clay tiles, crushed, gravel
• Clay/soil

 

[Oldboy]

Should the house be heated, and if so, to what temperature?
Isn't building foil and vapor barrier the same thing?
There should not be double vapor barriers.

Should any mat or similar be laid on the chipboard flooring?

There is always moisture in a crawl space, and it is a risk construction, but it doesn't feel super critical in a small duck house? Considering that many old trossbotten have lasted up to 100 years before the trossbotten boards have given up, this construction's trossbotten should be able to last at least 50 years? With not too flimsy trossbotten boards.

Landscape fabric does not prevent moisture. Unless you mean building plastic above ground? In any case, it is more temperature variations and condensation that create problems. However, your foundation is small, so with good ventilation, it should relatively quickly come into balance between outside and inside.

 

[Minde Passby]

Should the house be heated, and if so, to what temperature?
Isn't building foil and vapor barrier the same thing?
There shouldn't be double vapor barriers.

Should any carpet or similar be laid on the floorboards?

There is always moisture in a crawl space, and it is a risk construction, but it doesn't feel super critical in a small duck house? Given that many old subfloors have survived for up to 100 years before the subfloor boards gave up, this construction's subfloor should be able to withstand at least 50 years, provided the subfloor boards aren't too weak.

Ground fabric does not prevent moisture. Unless you mean building plastic above the ground? In any case, it is more the temperature variations and the resulting condensation that create problems. However, your foundation is small, so with good ventilation, it should relatively quickly reach a balance between outside and inside.

Thanks for the thoughts, I meant windproof paper, not vapor barrier.
I did as I planned, and it seems to be really good! The project is also a bit of a learning experience for me, because as you said, there shouldn't be any critical weight there. The house won't be heated, other than frost protection in the winter. Really thick walls, floors, and ceiling though

 

[Oldboy]

What may become a problem is likely the chipboard flooring. Chipboards and moisture are not a good combination. But it depends on how damp/wet it gets on the floor from the ducks.

In any case, it's just a matter of checking up on it a few times a year. If the chipboard, or anything else, turns out to have a problem, then you just deal with it at that time. That's when you appreciate simple constructions, sturdy constructions, and solid timber, and other robust natural materials. You don't have to tear everything down and build anew; usually, you can patch and repair, and improve any weak points.