Wainscotting and rising damp

[Rising Damp]

I have installed laboriously wainscotting in the ground floor of my old cottage - and put 15 mm polystyrene insulation behind it. I haven't vented it - and reading the forum see that I should have! the horizontal battens are continuous so there must be very little air movement anywhere! Now there seems to be moisture on the walls rising about 15 cms above the level of the wainscotting above the level, Any thoughts of a cure - apart from ripping it all off ( noooo!) and starting all over again.

 

[a twig]

Sorry, im not too clear in the construction. Is there an air gap between the polystyrene and the wall?

If there is an air gap you may be able to get away with cutting vent holes at regular intervals by using an oscillating multi tool and covering them with a nice brass grille or similar. If the insulation has fully filled the area between the timber and the wall then I’m afraid it’s an “all off” job

 

[Rising Damp]

Thanks for that. Yes - the wall is rough old masonry and the battens 1" by 2" so there should be an air gap. I will put in vents - you suggest regular intervals - how long would they be? 3 feet perhaps? I suppose it would have been better without any insulation at all? I didn't remove the old plaster either - just fixed the battens to it. Difficult to know what to do really. The house has always been plagued by damp - I inherited it from my mother who had tried many different measures to avoid the constant problem of repainting etc. The air in Cornwall s so humid anyway - especially after the last month's constant rain. But thanks again.

 

[a twig]

3ft intervals worked for my place - your mileage may vary! Ideally yes would have removed old plaster etc but then you are back into “all off” territory again!

There’s a thread here that might be worth a read and provide some inspiration:

Wainscotting to manage damp?

Our home is a generic North London 2 bed Victorian end terrace with little in the way of original features. We have quite bad damp at the base of the party wall which I think is due to a combination of the ground being clay, a concrete floor in the kitchen pushing damp up the walls, and modern...

www.periodproperty.co.uk

 

[Rising Damp]

Many thanks again. Will try vents and see if it improves. Not sure I can face taking it all off! Where did you get your vents btw?

 

[a twig]

I used these as budget was tight at the time and I needed 4 or 5:

https://www.ironmongerydirect.co.uk/product/hooded-louvre-vent-242-x-89mm-3973mm%C2%B2-free-air-flow-polished-brass-537678

There are much nicer available elsewhere if you have the cash / inclination - like the brass option on these:

Slotted Kenrick Air Vent · 9 x 3 Inch ·

A Black Aluminium 9 x 6" Air Vent, reproduced from a Kenrick original with a powder-coated finish in black or white. These air vent covers are a real credit and asset to any room. Original Kenrick Design British Made Quality Solid Cast Aluminium Tough Powder Coated Finish Complete with fixing...

www.yesterhome.com

 

[Rising Damp]

Thanks again for this. Somehow the cheaper option is more appealing! Interestingly I’ve noticed that the areas where the plaster had been removed before I covered them with panelling are not suffering from damp. I imagine plaster would wick up the moisture. One last question. Best remove the polystyrene then if I redo some sections of the wainscoting? Is it worth treating the back of the boards with some sort of preservative?

 

[a twig]

If there is still a decent air gap with the polystyrene in place (ideally 50mm but at least 25mm) then you could get away with leaving it I reckon. If it was me I would probably get rid but then I’m a lot less worried about insulating than a lot of people!

Depends on the wood you’ve used really, if you have used marine ply for the wainscotting then you’ll be fine, if it’s something like MDF then I would definitely slap some preservative, varnish or paint on the back to try and seal it.

Again this is all based on what I did in my place so you may need to tweak / adjust your approach to suit your situation

 

[Rising Damp]

Thanks once more. I'm using 8 mm beaded pine panels. Looks very pretty! Think Ill try to cut a thin slit at the top of the panelling and put a couple of vents above each of the horizontal battens - and just wait and see!

 

[a twig]

Looks great - will be really nice when all dry and finished! for you