Damp items in loft

patchyX2

I bought an inflatable paddleboard this summer and have stored it in the loft over the winter.

I went up there this morning and noticed some damp patches under the boards. The boards are stored in a bag along with paddles, some wetsuits, towels and lifejackets.

I took the bags out and looked inside and there's appears to be a bit of condensation on the plastic items (the board, fin, paddle, etc), so I'm assuming this is what's causing the damp patches under the bags.

What's weird is that there's no other signs of condensation in the loft. There's certainly no visible condensation on the roof, nor on any other items in the loft (including things like buckets, plastic trays/boxes, tins of paint, tools, cardboard boxes, etc). It doesn't smell damp either.

There's plenty of insulation, and reasonable ventilation.

Just a bit confused as to why only one item gets damp?!! Any ideas?

Brie

sounds like something didn't get dried enough prior to storage.

twopenny

Quite possible they looked dry at storage but damp in the seams or some such.
I've stored my stuff in loft or garage but always dry through on a hot day before packing.

Also check the edges of the loft are clear of insulation allowing it to be ventilated.

Mistral001

twopenny said:

Quite possible they looked dry at storage but damp in the seams or some such.
I've stored my stuff in loft or garage but always dry through on a hot day before packing.

Also check the edges of the loft are clear of insulation allowing it to be ventilated.

Agree with this.  You can check that insulation is not covering the vents, by switching off of all lights in the roof space or any hand torches you have and look in the direction of the eaves. If you cannot see some patches of daylight there, then the vents probably are blocked. 

mexican_dave

I guess your paddle board is made of a kind of plastic. If your loft items are like mine, other items in the loft are in cardboard boxes which are permeable to water vapour and let the water vapour through and out into the open loft, where it diffuses out of the roof space. Small plastic items may be too small to hold-on to the water vapour, not enough area, so don't seem damp. Reckon what is happening is warm air in the house is passing through the ceiling carrying moisture (water vapour). Now plasterboard & the like are permeable to water vapour, so the water vapour passes into the loft. Then it enters the bag containing your board where because of lack of draughts (it's in a bag) it hangs about. When enough water vapour has accumulated the water condenses (cold loft) on the underside of your board. Hey presto, my board is wet! Simple solution if you have room in the loft stand the board on edge so water vapour can pass around it. Let us know how that goes.

Del_III

The boards must be at or below the dew point. The cold air is dry at this time of year, even when it's raining. It shouldn't really happen in a well ventilated loft. Does your bathroom extraction fan pipe run through the loft? Sometimes these pipes detach and moist air blows straight into the loft.

You should take some readings to see how damp it is up there. Put the results into this calculator and it will give you the absolute humidity of your loft, as well as the dew point. https://man-maths.co.uk/calculators/damp-and-humidity-calculator

ashe

Chuck a few lap vents in as well if you don't have any. Extra ventilation will help if it is condensation, but does sound like its something not dried properly.

mexican_dave

Del_III said:

The boards must be at or below the dew point. The cold air is dry at this time of year, even when it's raining. It shouldn't really happen in a well ventilated loft.

Del_lll says the air is dry this time of year but overlooks the fact that moisture passes out of your house through the porous ceiling where we agree it hits the cold surfboard. Where as I suggest it condenses. Suspect you can do Del_lll's calculations and be none this wiser, but good luck all the same.