Log cabin, condensation

[PerryBach]

Hi, I've recently constructed a log cabin on an existing wooden deck; external 5" log lap, internal pallet wood cladding, rockwool 50ml insulation, roof fiber glass profile sheets, two large double glaze windows and door. Following completion of external cladding condensation droplets started forming on the roof sheets to the degree that when you closed the door heavily you had a shower if you were inside. can anyone offer a solution to rectify.

 

[JohnD]

how is it ventilated?

How far do the eaves of the roof extend beyond the walls?

How do you isolate the deck from the floor and interior of the cabin?

How much insulation is of the walls, and how much of the ceiling?

What vapour barrier do you have between the ceiling and the roof?

Some photos may help.

 

[PerryBach]

John

The profile sheets sit on top of the ceiling joists; air circulates between the profile and the joist

The eaves extend beyond the walls approximately 12"

The deck sits on 8 x 2 joists on a slopping bank ranging from 10" to 18", the deck is the floor of the cabin.

The walls are constructed by 4 x 2 uprights and noggins with 50mm insulation, there's no insulation on the roof.

There's no vapour barrier.

 

[^woody^]

I can't see a resolution unless the room is suitably heated. Ventilation alone won't cut it

 

[scbk]

Is that a gas heater?
You do know that they put out a lot of moisture? First thing to do is ditch that, then insulate the roof.

 

[PerryBach]

scbk, hi yes
it's only a temporary measures the plan is to install a room heater wood burner

 

[PerryBach]

My thoughts are to experiment with fixing polycarbonate sheets to the underside of the profile sheet on a third of the area and see what happens, any opinions?

 

[mikeey84]

That polycarbonate is still going to get cold, so water vapour will condense on it, and you will get indoor rain.

As said, heating that doesn't kick out a load of moisture, and roof insulation will be the best solution

 

[JohnD]

the deck is the floor of the cabin.

no insulation on the roof.

There's no vapour barrier.

Fix those three things and remove the gas heater.

 

[JohnD]

I can't see a resolution unless the room is suitably heated. Ventilation alone won't cut it

My shed has ventilation but no heating

And no condensation.

 

[^woody^]

My shed has ventilation but no heating

And no condensation.

As does mine. Mine does not have a mass of plastic sheets for a roof though, does yours?

 

[JohnD]

Yes, twinwall polycarbonate.

 

[^woody^]

A Christmas miracle to defy all known science. Are you following the star again this season?

You could probably share with us how to stop the condensation forming on the outside of our car windows when its parked on the drive too, on these cold days and nights. Ventilation alone sees adequate.

 

[PerryBach]

JohnD
Am I right in thinking, could I fit a vapour barrier direct on top of the decking boards and then glue 1/4 ply or similar, directly on top of the vapour barrier, could that prevent the moisture coming up from the ground below if it was sealed correctly?

As far as the ceiling sheets go they are going to have to be replaced with either a cold or warm roof construction?

The gas fire is just a temporary measure and will be removed later on.

 

[JohnD]

I'd probably space the floor off the decking and have a ventilated void, and an insulated floor.

If the decking boards are fitted fairly loosely they can probably ventilate through the gaps.

I think the decking boards are likely to be wet if they are exposed to rain outside the footprint of the building, so they need ventilation rather than a tight cover so the damp can escape.