Period Damproofing

[Flyfisher]

One of our rooms has suffered from decades (at least) of high external ground levels, which I'm finally getting around to fixing. The wall in question is part of the C17 addition to the house but I suspect the external ground level was raised when a path around the house was added at some time without bothering to do any digging. Whatever the actual history the consequences are clear.

This is the context:



The wall in question is west facing. The ground level was not quite as high as it first appears because there was a small retaining wall holding back the lawn from the path, but you can just about see the line on the wall where the ground level was before - about one foot above the internal floor level. I've now dug this down to about three inches below internal floor level.

After clearing all the undergrowth that was obscuring the wall, I noticed these peculiar features:



They are present along the entire length of the wall and were above the raised external ground level. Here's a close up view:



It looks like a round hole about two inches in diameter covered with chicken wire, presumably to prevent vermin entering the wall.

I'm guessing that the raised ground level caused the base of the wall to be damp (actually I know that for a fact, having removed the rotten skirting board!) and that these 'features' were subsequently added to the wall in an attempt to improve ventilation within the wall and, hopefully, help to dry it out - though I can't see how they could possibly have done anything about the damp in the lower part of the wall given the raised ground level.

I've never seen such features before (though that's not saying much!) and am wondering if such things were commonplace, or even if they were the period equivalent of damproofing snake oil? Any ideas?

 

[stephenh]

FF - try this for size ?

http://www.heritage-house.org/holland-damp-proofing-system-another-expensive-fraud.html

good luck with the damp
stephenh

 

[MatthewC]

That's an interesting link, Stephen, very helpful.

FF - you guessed "damproofing snake oil" and you were right! What a con.

 

[Flyfisher]

Yes, thanks Stephen - interesting article. I vaguely remember reading something somewhere about terracotta pipes inserted into walls to control damp but I thought it was a modern thing and didn't realise the idea went back so far. It seems obvious now that such things could never work if surrounded by cement mortar but I wonder if the basic idea would work better if the pipes were bedding within lime mortar? It would at least increase the surface area available for evaporating moisture, though I suppose a simple lime-only wall would have more than enough as it is and such tube would only increase the total area by a very small percentage. Incidentally, the wall itself is basically a rubble wall built with a very weak lime mortar (which has crumbled and flowed away in places), so I'm pretty sure the damp issues are not the result of widespread 'cement abuse' but simply a consequence of the external ground level being about 12 inches above the internal floor!

Oh well, yet another reminder that scams are not a modern invention. I shall leave them in place, though I'm putting more faith into the lowered external ground level helping to reduce, and hopefully cure, the damp problem.

 

[JohnArmer]

I have these in my house. On the outside they're covered with little triangular brass vents, which make them look rather masonic I think.

We've just had the front of the house repointed in lime and we've kept them. I don't think they're doing much harm even if they're not doing much.

 

[Roger H]

That's some damn fine ribbon pointin' !

(Pleased to see you have had it removed....)

 

[JohnArmer]

All gone now, Roger

Pics to follow when the Hessian comes off.