Query Re: Vent holes? in wall

[asimon]

Dear Forum,

I have a period property dated around 1872, I having some work done to the exterior, but wanted some clarification with regards to vent holes along the bottom of the house, please see drop box link to view images.
The first 2 pictures, are full pictures of the rear of the property, the next 2 images show the hols on the rear extension of the property, the following 2 images off rear of the property, I do have a crawl space which covers all of this section of the house, you may also be able to see underneath these holes some drills holes , I presume this may have been for some DPC treatment which I have records saying this was done in 1990, the next image is of the side of the house and the final 2 are the front of the house.

Some of the holes that were exposed, i insert a broom end, into, to see if went right through, however the ones i tries did not.

https://www.dropbox.com/sh/4rh828fvdqudtqc/AABGYxeGqiamXBaNnSfDef1Ia

I'd be grateful for any useful information / advice with regards to these holes, should they stay or be covered up,

Thanks in advance

 

[Keith Bowman]

Those look like the ceramic (blind) tubes marketed as a cure for damp some years ago. Presumably they were no more successful than a coating of snake oil

 

[plasticpigeon]

The render seems to be dropping off quite easily, it seems to have been put onto a painted wall. perhaps you will get lucky and it will come off without much damage. However it looks like it will take a lot of work to get the walls looking good again. Those holes are strange. Sounds like Keith knows what he's on about. I wouldn't worry about replacing them with bricks of that is what you were thinking.

 

[asimon]

Thanks for the feed back so far, my builders were concerned as to whether they could render over them or whether they need to stay, but seems though they serve no current purpose, more comments welcomed

 

[Flyfisher]

Does the house show any signs of damp at the moment?

Dear Forum,
Some of the holes that were exposed, i insert a broom end, into, to see if went right through, however the ones i tries did not.

It looks as if some of the tubes are inserted below the internal floor (I'm assuming a suspended floor?) and some are inserted above it. Which ones did you insert the broom handle into?

If the walls are solid and the tubes are closed then, as Keith points out, it's difficult to see what good they could be doing, especially the higher level ones, which suggests they could be safely rendered over.

However, it's good practice for the underside of a suspended floor to be properly ventilated so I'd be thinking about sorting out a more effective solution. As it sounds like you're planning to have the wall re-rendered, perhaps some suitable airbricks could be installed? If they are set to protrude slightly then they'll end up being flush with the new render and should be quite neat.

 

[88v8]

Yes, useless damp 'treatment' tubes. Nor use nor ornament.

In pics 7 & 9 there are grilles that presumably ventilate the crawl space. It will be as well to ensure that there are vents in all four walls, and that there is decent airflow through them. You might also consider whether more, perhaps smaller, vents would be useful in corners, where there can be a dead zone with no airflow.

Cast-iron vents tend to have a better open area, the terracotta ones are pretty useless.
These are amazingly cheap.
http://www.ebay.co.uk/itm/Quality-Cast-Iron-air-Brick-Vent-Air-brick-Cast-Air-vent-NEW-Victorian-Pattern-/131226179563?pt=UK_Antiques_Architecural_RL&hash=item1e8db097eb
Paint before installation and after.

Ivor

 

[steveb]

Looks remarkably like this:

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

 

[Keithj]

Those things had been fitted into the walls of our place, too. We also had those daft little sausages of plasticky stuff that are injected into holes drilled into the walls and supposed to permeate through the structure to stop the damp. They ended up as plastic plugs in the holes - same shape and size and with no permeating whatever.

We looked at them in disbelief when the rotten sole plates (and the concrete smothering them) were removed. They're in the same league as "rising damp" and "tanking". I remember school physics lessons many decades ago and measuring capillary effect and osmosis. We managed almost an inch with the first, and a little further with the second (but not in lime plaster!)

 

[Keith Bowman]

...... I remember school physics lessons many decades ago and measuring capillary effect and osmosis. We managed almost an inch with the first, and a little further with the second (but not in lime plaster!)

I'm not going anywhere near the rising damp question (!) - but surely you ought to be able to get more than one inch of capillary effect or oil lamps would stop working long before they ran out of oil. Or do oil lamps and candles work by some other effect entirely?

 

[kreyszig]

Capillary action depends (amongst other things) on the radius of the pore space the fluid is travelling through, and is inversely proportional at that. I.e larger pores, less capillary pressure. The pore space between wick fibres will differ to that in bricks. The fluid properties of oil vs water are also important of course, as well as the effect burning the oil may have to draw fluid up the wick (although this must be similar to evaporation, I would guess)

 

[Keithj]

Yes, oil or paraffin will "wick" further than water. We only played with water at school, so I can't comment on oil. What water won't do is wick several feet up a lime plaster wall (for example).

I hope!

 

[MatthewC]

The fluid properties of oil vs water are also important of course

The surface tension - it must be lower for oil-based solvents than for water, and that makes it easier to get into the smaller gaps. I think then the surface tension reacts against the sides of each gap and pulls the fluid up - if the gap is too large then it doesn't go up, as kreyszig said. Then the density of the fluid must contribute to the dynamics as well (think mercury!)

 

[kreyszig]

(Deleted)

 

[Matt Green]

The idea is that water moves into the ceramic tubes and drains or evaporates out of the opening. The novelty of the theory is far outweighed by the vandalism of the practise.

 

[Penners]

I've never heard anyone sing the praises of that damp-eradication solution. However, I'm also not aware of any credible testing procedure that has proved or disproved their efficacy (although this may exist). So I think a brief pause for reflection is in order.

If the house is not damp, then this may or may not be attributable to those ceramic doobrie-ferkins. So if they're not actually doing any harm, it might be advisable to leave them in place and not to render over or block them.

If that idea appals you, aesthetically speaking, then it's up to you whether you take the chance or not.