NATURAL CEMENT or plastic membrane

[binsy0]

We are renovating a Purbeck stone cottage that has extensive damp problems. It has penetrating and rising damp. The outside of the building has been re-pointed about 20 years ago with concrete pointing hence trapping water into the building. Also the interior floor is below the outside ground level by about 6 inches hence some rising damp. The house also has no central heating and has been empty for 12 months.

We plan to rake out the concrete pointing and use lime mortar and also lay a concrete ground gutter to remove most of the rain that runs down the facing wall. Our problem lies inside. We have been advised by different people to do different things.

1: to use an egg box construction plastic membrane, the likes of delta membrane or basement systems and then plaster over the top of this.
or
2: use NATURAL CEMENT directly onto the stone on the inside as a tanking method and then plaster over the top of this

We haven't used NATURAL CEMENT before. We want to do the job properly as we don't want to be repairing damp spots every few years.

Does anybody have experience with NATURAL CEMENT ?

 

[biffvernon]

What's Natural Cement?

 

[Nemesis]

Try a google... I think it's adspeak... hydraulic lime I think.

Quote:

Prompt natural cement is an incredibly fast setting cement (controllable from just ninety seconds!), that can set underwater and can even be used for stopping leaks! Regular customers for this remarkable material refer to it as an essential tool.

 

[binsy0]

Natural cement

It has been recommended by our architect, it is apparantly as quoted
" natural cement is an incredibly fast setting cement (controllable from just ninety seconds!). An added bonus is it\\\'s exceptional shelf life. Regular customers for this remarkable material refer to it as an essential tool.
Natural Cement is a very simple material with some complex characteristics, manufactured from Argillaceous Limestone (Limestone containing some clays) it is simply mined, fired and milled. Nothing is added to it, nothing is taken away. Having been in use for over a hundred and fifty years it has been tested and proven well beyond the abilities of Ordinary Portland Cement.

 Extremely fast set, which is controllable
 Waterproof and sets under water
 Approved for use with drinking water
 Can be mixed with sea water
 Low shrinkage
 Fully controllable setting time, from 90 seconds to 90 minutes
 Beige colour develops on exposure to sunlight
 Completely natural
 Resistant to chemical, acids and alkalis
 No additions whatsoever

I believe this stuff is only mined in a few places around the world, The south of France being one of them. You can then apply a breathable plaster over the top.

Just wondered if anybody has tried it? looks like it will be cheaper and more in keeping to use than plastic membrane

 

[Nemesis]

It's actually hydraulic lime. How breathable it is and how useful in this situation I wouldn't care to say. Not much point in putting lime plaster over something not terribly breathable. It may be more eco friendly than ordinary cement but if it's very strong hydraulic stuff it may simply act in the same way. It also could be hard to remove if it all goes wrong - reversibility is a useful asset when dealing with historic buildings.

I'd be wary of using it here without a great deal of thought and research.

 

[binsy0]

Thanks,
You see this seems to be the problem. Not many people know much about it and I currently have little knowledge of the product. And it only appears to be sold by a limited number of outlets. I would love to find somebody who has used it with good or bad effect.

 

[Nemesis]

Can I suggest you give SPAB (free helpline... ) a ring and see how they feel about its use for this?

I'm sure others will chip in here too and SPAB may take a little while to ask others but it's pretty expert advice.

I urge caution frankly. Hydraulic isn't rare or unusual stuff, but in this application unless it's very hydraulic I can't see it being useful, and being very hydraulic ... ditto!

http://www.spab.org.uk

 

[Manny]

Can't you reduce the level of the ground outside?

 

[Nemesis]

That is of course the problem - penetrating damp - along with the lack of heating which can't be helping.

 

[Penners]

use NATURAL CEMENT directly onto the stone on the inside as a tanking method

Whether Natural Cement (two words that I've never seen in the same sentence before) is a lime product (as Nemesis suggests) or a cement product, I certainly wouldn't use it for tanking. I find it hard to believe that lime or cement (without various specialist additives) will create an entirely impervious coating on your wall - which is what I infer from the word "tanking".

The "sets under water" claim seems to be making a virtue out of the obvious - won't lime and cement mortars both do that anyway?

 

[Nemesis]

Hydraulic lime sets under water, this stuff is natural hydraulic lime.

 

[Penners]

That's what I thought. Cement does too.

 

[binsy0]

I'm getting more and more confused. I have gone back to 2 suppliers of Natural cement (NATCEM 35) today and they both confirm that is would be ideal for tanking as it totally stops water and is more flexible than concrete. Both these companies are big suppliers of lime mortor and believe that the 2 products lime mortor pointing on the outside and natural cement on the inside will work with eachother.

I will speak to SPAB tomorrow to see if it throws any light on the subject. The thing is, if it was just the suppliers telling me it was good I would dismiss it. The problem is my architect has recommended it as a solution and up to then I had never heard of it.

 

[Gervase]

Natcem 35 is rather more than hydraulic lime - it's a modern take on traditional Roman cement, made by the high temperature kilning of silicaceous limestone.
As such its behaviour is very similar to OPC, but with an even faster set. It is completely waterproof, and thus can be used for tanking.
It is bloody expensive, at more than £1 a kilo. If you were building a large underground cistern or an aqueduct, it would be the dog's danglers.
But, with a floor differential of just six inches, why in the name of Smeaton's underpants is your architect suggesting tanking witht he stuff in your cottage? A French drain or culvert along the external wall will solve the problem without even the need for a concrete gutter. Repinting with lime and attention to the guttering and rainwater system should take care of the rest of the penetrating damp.
I would strongly suggest you make contact with a RICS surveyor with experience in traditional buildings, rather than rely on the advice you have been given, which would be more suitable for a cellar in sodden ground than a stone cottage.

 

[Nemesis]

Well that's about what I thought but didn't say it as eloquently. Seems totally OTT. I have a nasty feeling though that it will keep on rearing its head for this sort of application...

PS did Smeaton have underpants or smalls? Or did he go commando...

 

[binsy0]

OK thanks, it seems to make more sense. I guess the architect has suggested it as the house is on top of a hill looking out at the Atlantic Ocean and every inch of the south and south west walls on the inside is not just damp but dripping wet. All the main beam ends have rotted from years of damp. All the plaster has gone hydroscopic and the electtric sockets constantly fuse because water drips out of them.
I just want to stop the water once and for all.

 

[Nemesis]

Struth! I thought Northumberland was wet...

I think it sounds attractive at first but I also think that a variety of solutions. rather than this quite aggessive one, may be the answer.

Architects though aren't in general totally in tune with the stuff experts in damp are... and by that I don't mean a man with a van and a meter.

 

[binsy0]

Thanks for the advice. it sounds like I have some homework to do