Unimportant (but interesting) question

[frahkn]

As above - this is of no importance but a bit strange.

 

The ceiling/deck head in my boat is 3 inch boards which run longitudinally. These are on transverse supports at 14 inch centres and each board is painted white in an eggshell type finish.

 

Recently I can see darker bands where the supports are. These cannot be removed by cleaning but presumably will have to be painted over.

 

My question is what explanation can you propose as to why the discolouration should be where (and only where) the underlying supports are?

 

Edited June 15, 2019 by frahkn

[mrsmelly]

Damp coming through from the battens? If the battens have absorbed moisture over time.

[Guest]

14 minutes ago, mrsmelly said:

Damp coming through from the battens? If the battens have absorbed moisture over time.

That was my first thoughts. Our boat tends to do similar on the lining nearest to the fire, mainly in winter. Something is sweating somewhere. 

[BilgePump]

^^ wot @mrsmelly said

 

could simply be condensation and not an actual leak causing moisture. Timber lives, it will swell, contract and eventually deteriorate. The battens are touching the hull and will be the first bits to suffer from any moisture. Do make sure though that the water isn't coming in from any roof vents etc first. Boats and headlinings are always fun! 

[Slim]

Damp!

The deckhead of my boat ois lined with oak faced ply. Over the years the ply has stained in three 10 x 40 mm patches. Obviously the oak reacting to moisture. No great shakes in the order of things. Unfortunatly it's immediatly above my bunk and I wake up to it every morning. ?

Quote

 

 

[zenataomm]

16 minutes ago, Slim said:

 Unfortunatly it's immediatly above my bunk and I wake up to it every morning. ?

 

The time to worry is when you don't

[Iain_S]

Condensation.

The insulation is thinner where the supports are, or possibly the wooden support is the only insulation at that point. (Deckhead screwed to batten, which is attached to steelwork) 

[nbfiresprite]

Paint discoloration from heat transfer from the roof due to thermal bridging.

[David Mack]

Yep. Condensation on the relatively cold sections of the boarding over the battens. You are probably getting a small amount of mould growing in these colder areas, hence the darker bands.

[Sea Dog]

Gnomes (with little step ladders) sneak in at night and quietly run their little fingers along the lines of the battens. No-one knows why they do it, but their mucky little hands mean they eventually darken the wood and visible lines appear where the battens are.  The only way to prevent it is to keep moving the battens so that the deck head darkens evenly.

[Jim Riley]

stainblock of some sort, followed by a repaint. that'll sort it.

[frahkn]

4 hours ago, Sea Dog said:

Gnomes (with little step ladders) sneak in at night and quietly run their little fingers along the lines of the battens. No-one knows why they do it, but their mucky little hands mean they eventually darken the wood and visible lines appear where the battens are.  The only way to prevent it is to keep moving the battens so that the deck head darkens evenly.

You might have something there! That would explain the occasional mark on the floor in the morning - step ladder feet - now I'm going to have to apologise to the dog.