Rising damp abroad

[elgee]

Hi there. I have a problem that is pretty common for houses built in the Mediterranean, Aegean region.

Most of the older houses ie. 5 years old or more, buil to earthquake standards, with reinforced concrete sub-structures and ceramic brick/block built walls, lacked a proper dpc. My house is built straight onto a rock-cut terrace and sits on a solid concrete floor. Consequently, there is a problem with rising damp up to about 1 meter from outside ground level.

The problem is made worse because: 1) unwashed sand was used in the mortar, so salt blows the finishing plaster skim off the walls, 2) the bottom meter of the outside has a very attractive natural stone cladding which I am hoping to retain.

Do you think the dpc creams would work, or have you any other suggestions?

I was planning to do the work in the early Autumn when the walls are dry (the problem arises in the winter months January onwards). Is this a good time to do the work, or is it best done when the walls are damp?

Any suggestions would be most welcome.

Thanks

[ultimatehandyman]

I think that an electro osmosis damp proof course may be better than the cream especially as the property does not have a cavity.

[elgee]

Thanks for the quick response. I looked at the link you kindly provided and it looks very interesting.

The problem is that we are only in the house for holidays (until my wife retires), so for most of the time the electricity supply is off. When I was looking for workable solutions to the problem I was attracted by the injected cream idea because it is something I could do myself.

There are firms in Turkey who do this kind of thing, but they have had quite a lot of bad press. I don't know whether this is because the product/s don't work, or because they have not been installed correctly.

If the creams work I was going to go out to do the work, depending on when would be best, either now when the walls are dry, or later, January onwards, during the rainy season if that would be best.

The two questions I need answers to are:

1) Do the creams work (or any other injectable system, for that matter)?

2) When is the best time to apply them - a couple of months before the rains come, or during the rains?

If you could answer these I would be most grateful.

Regards,
Les Greenwood

[DAZDEL]

are the internal walls just plastered, (ie) sprayed plaster. Or are they sand and cement, then skimmed.

[elgee]

Hello Dazdel.

Thanks for the response. They are sand and cement then skimmed. The salt crystals have caused the plaster skim to come away from the rendering in places, the rendering seems pretty much intact, but is probably part of the problem because it sits on a concrete floor with no membrane.

I was hoping to find a product that would allow me to inject a dpc into one of the lower mortar layers, as well as to saturate the lower levels of the sand cement rendering where it meets the comcrete floor (another place that water can penetrate from).

I'm not sure whether the new generation of cremes are best used on an already wet wall, or on a dry one? I did read somewhere that the older cremes (as opposed to high pressure liquids) did not cure, so that when it rained, even months later, they would still react with the water and spread. They were saying that the 2nd generation cremes were good for already damp walls.

I can either go before the rains, while it is still good weather, which will make the job easier, or, I can go in the winter when the walls are wet and do the job then.

Can you recommend a product &/or technique for at least cutting back the amount of damage to the skim layer?

Thanks,

[DAZDEL]

Hi elgee
Do you have the same problem with the internal walls as well, Also is there a like a tide mark, which defines the height of of the damp.

[elgee]

There is no problem with the internal walls, I think they sit on quite a thick concrete pad whereas the outside walls are probably layed straight onto the underlying stone.

The earthquake proof build consists of reinforced uprights at each corner - presumably anchored into the rock terracing underneath - and the gaps between filled with a single brick - typical ceramic type, but because the walls are designed to be light and collapsible in the event of an earthquake, they are not layed in the same way as the British standard.

It seems that they can be put together with a minimum amount of mortar on the horizontal layers and just enough vertically to hold them together. This probably doesn't help when it comes to using dpc creams, but it is the only thing I can think of to use. It would help, I think, to saturate the bottom of the concrete facing on the walls as well.

What do you think?

[DAZDEL]

http://www.cercol.com/uk/index.php?pagi ... ucts%20for%

Hi elgee, sounds like you have secondary efflorescence. The link above is the plaster i use here in lanzarote, as the houses here have no dpc, and are built the same way as yours. secondary efflorescence will destroy the gypsum skim coat you have, and the paint. The stone work on the outside walls is stopping the wall from breathing, so the salts will find a easier route, the inside wall. As you want to keep the stone work outside, its important that the inside can breath, (ie) let the salts pass through. Using this product and a quality mineral paint, or lime paint will let the salts pass through causing no damage. This is a breathing problem not a sealing problem. If you were to seal the wall the salts will just go higher, i've seen 10 metres before where someone had used fibre glass and resin to seal a wall. Even sand and cement that keeps getting scraped and painted, using the wrong paint, the salt will eat the surface away. Hope this gives you some idea of what you are up against. For more info, let me know

[elgee]

Thanks Dazdel. That's very useful info. I'll get back to you in a couple of days - my son is getting married tomorrow, so I'm going to be a bit tied up.

Thganks again,

Les