sweating concrete slab in outhouse

[jazzbhatia]

Hi all

Been to see an outhouse that was built 6 years ago. The floor is of concrete construction (makeup is unknown at this stage) which for some reason has 2x4 timbers followed by flooring boards and finished with carpet

The timber floor was completely replaced 3 years ago due to excessive timber rot and again same thing

There does doe appear to be any water leak but the entire concrete slab is wet to touch

I believe this is due to the slab sweating but am puzzled why someone would have placed a timber floor on top of the concrete slab

Before digging trial holes to determine the slab makeup have you guys experienced this.

 

[John D v2.0]

Yes, our garage floor is dry until you cover it, then it's wet.
Basically lack of damp proof membrane or incomplete DPM means water needs to evaporate quicker than it soaks in.
Also timber should not be installed in an unvented unheated void even with adequate damp proofing.
Basically either need to strip out the timber and revert neba toa floor that won't be damaged by water ingress, or rip out and install a DPM then timber back on top with adequate ventilation.

 

[^woody^]

Either a layer of Rightguard or polythene on the concrete will deal with the sweating.

 

[jazzbhatia]

Yes, our garage floor is dry until you cover it, then it's wet.
Basically lack of damp proof membrane or incomplete DPM means water needs to evaporate quicker than it soaks in.
Also timber should not be installed in an unvented unheated void even with adequate damp proofing.
Basically either need to strip out the timber and revert neba toa floor that won't be damaged by water ingress, or rip out and install a DPM then timber back on top with adequate ventilation.

Hi thanks for your reply. The timber floor will indeed need to be removed, I really can’t see its purpose as the concrete floor appears to be in decent condition

 

[jazzbhatia]

Yes, our garage floor is dry until you cover it, then it's wet.
Basically lack of damp proof membrane or incomplete DPM means water needs to evaporate quicker than it soaks in.
Also timber should not be installed in an unvented unheated void even with adequate damp proofing.
Basically either need to strip out the timber and revert neba toa floor that won't be damaged by water ingress, or rip out and install a DPM then timber back on top with adequate ventilation.

Either a layer of Rightguard or polythene on the concrete will deal with the sweating.

Rightguard?

 

[IWalkLikeHimaMartian]

Condensation.
http://www.concreteconstruction.net/how-to/sweating-slab-syndrome-1_o

With an uncovered concrete floor the condensation is allowed to evaporate.
When the concrete is covered, including by dirt etc, the evaporation rate is significantly reduced and sweating becomes obvious.