damp proofing

[RIK]

I've been offered damp-proofing of exterior walls by silicon injection. Has anyone experience of the effectiveness or otherwise of this treatment?

RIK

[cooperlola]

In the UK, yes.  It was useless.  My experience only, you understand!

[Nearly Retired (I am now)]

A corner of my house in England was damp-proofed this way by the previous owner and it has been fine for 20 years now. The theory is that the bricks absorb the silicon in all the little pores and so water cannot get through. A fine theory, seems to work in bricks but I'd have grave doubts about using it in stone, lime mortar and rubble filled walls - of which I've got lot in France. In the unlikely event that the method really completely prevents moisture ingress in this situation then the pointing dries out and the walls fall down. Take care. 

[Nick Trollope]

[quote user="RIK"]

I've been offered damp-proofing of exterior walls by silicon injection. Has anyone experience of the effectiveness or otherwise of this treatment?

RIK

[/quote]

It works on absorbant UK bricks, but not on granite! I have seen plenty of Brits ripped off by a local Estate Agent getting work for his family.

 

[cooperlola]

I'll clarify that the place referred to in my above post was 1879 brick built (14" walls and quarry tiled floor straight onto the earth).  The survey showed damp walls in the kitchen and hall (where the tiles were) when we bought it.  We had the silicon injections done and the walls were still damp (although it varied, according to weather and season) afterwards.  There is of course a chance that the installation was poor!

[Deimos]

My understanding is that some walls require a degree of damp to stay up. Dry them out and they will fall down.

I have also notices that the French seem far less concerned about a bit of "damp" whereas Brits are paranoid about anybody mentioning it. Of course not talking about "mould on the walls" type damp. I suspect that a lot of modern treatments can cause as many problems as the solve. Most builders tell me that old houses should be allowed to "breath" and then there is no big issue.

Also, I have come across the same types of companies in France as in the UK - the "specialist" people who will treat for non-existent problem for a vastly inflated price. I had some wood treatment people round who showed me all sorts of pictures of nasty bugs eating timber - to which I commented that it was a great relief that I did not have any such things in my roof. They spent about 2 hours trying to convince me, gave a a ludicrous quote then tried calling their boss for a "better deal "as they were "in the area". Eventually I told them there was no way on earth I was making any decision there and then so they immediately left.  Of course I have no idea about the people quoting OP.

Ian

[cooperlola]

Deimos's post reflects the views here.  Most of the traditional farm houses and buildings like ours were built to allow the walls to breathe and as a consequence do alter in humidity according to season, as they should and were designed to.  A local builder who had a look at our house was more concerned that the previous occupants had used incorrect materials to render a couple of the walls - this appears to be much the greatest cause of real damp problems (the mouldy walls Deimos mentions) than anything else.  Could that be the op's problem? It rather depends on the construction/materials used in his/her own property, doesn't it?

[BIG MAC]

Silicone injection will work reasonably well with brickwork, that's it.

If you require a dry stone wall you would be better with a vertical dpm and drylining.

[oliveau]

[quote user="RIK"]

I've been offered damp-proofing of exterior walls by silicon injection. Has anyone experience of the effectiveness or otherwise of this treatment?

RIK

[/quote]

We had a problem with water penetrating the concrete block walls at the base of the sou-sol, which was cured by excavating down and applying a coat of black bitumen to the blockwork.

It really rather depends on the materials, and the initial cause of the damp. If you have an old house, it probably has not got a dpc. I suggest professional advice from a 'maitre d'oeuvre'.

Peter

[Gyn_Paul]

[quote user="Deimos"]

My understanding is that some walls require a degree of damp to stay up. Dry them out and they will fall down.

I have also notices that the French seem

far less concerned about a bit of "damp" whereas Brits are paranoid

about anybody mentioning it. Of course not talking about "mould on the

walls" type damp. I suspect that a lot of modern treatments can cause

as many problems as the solve. Most builders tell me that old houses

should be allowed to "breath" and then there is no big issue.

Also, I have come across the same types

of companies in France as in the UK - the "specialist" people who will

treat for non-existent problem for a vastly inflated price. I had some

wood treatment people round who showed me all sorts of pictures of

nasty bugs eating timber - to which I commented that it was a great

relief that I did not have any such things in my roof. They spent about

2 hours trying to convince me, gave a a ludicrous quote then tried

calling their boss for a "better deal "as they were "in the area".

Eventually I told them there was no way on earth I was making any

decision there and then so they immediately left.  Of course I

have no idea about the people quoting OP.

Ian

[/quote]

The other cracking wheeze is the lads who come round trying to sell you

a treatment to remove the (perfectly harmless) litchen growing on the

roof tiles. Pressure washing followed by a perfectly useless silicone

spray. After 15 minutes of hard sell I finally winkled a price out of

him (just out of interest): 4000 Euros for a single-storey building

covering 90sqm !

For someone who claimed not to speak any English, he seemed to

understand "You must be joking!" well enough. Possibly it was the

laughter as I shut the door on him which gave him a clue.

[Nick Price]

The use of incorrect materials is indeed one of the primary causes of damp in walls - or so says my brother who is one of the very few specialist building surveyors qualified to work on major UK National Trust properties. Over the years that I have owned my French house I have had many worthwhile discussions with him concerning appropriate building techniques for my 1849 Charentais Logis (Large [lime]Stone House). I'll summarise a few related to this topic here.

1. Use traditional materials. Lime and local sand. Do not use cement:

Lots of people have commented in this forum on this before but something that I have leaned from my brother is that a "creppie" i.e. a lime/sand based wall render is actually a sacrificial material. Its job is to extract water from the wall by evaporation rather than to prevent it entering in the first place by being impermiable as a cement render would be. The continuous process of water evaporation causes the creppie to fail regularly - every 50-80 years - during the lifetime of a house. Why is there water in the wall in the first place? Many reasons, but principal would be lack of DPC. Why not use cement? Because, being impermiable, it doesn't let the water that is already in the wall evaporate out. There are other reasons such as material elasticity which I won't detail here except to say that old buildings move slightly so use an elastic material - lime.

2. If the wall was creppied or butter jointed (more lime morter than stone left showing), do not replace with small joints between the stones. Renew the jointing/creppie as it was done originally. The original creppie/jointing method was a functional decision not an aethetic one.

3. Do not allow water to accumulate at the exterior base of a wall. Don't plant shrubs next to the wall and do encourage rain water to flow away from the wall base.

4. Repair guttering and/or make sure that roof overhangs do not allow water to drip down the walls

5. Install exterior drainage to take water away from the house.

6. Keep the house warm in winter. Yes, it costs money, but that is the price you pay for owning an old house.

In summary, and to agree with cooperlola's previous post, allow the wall to breathe to extract the water that is already in the wall rather than covering the wall to prevent water from penetrating or by trying to prevent water from rising via synthetic methods. And yes, you may have to live with a slightly damp wall from time to time. 

Two points of clarification:  (i) The points above refer to traditional stone houses built prior to 1900'ish and the introduction of 'modern' building methods and materials.  (ii) I am by no means an expert, but these few rules have helped me turn a fairly damp house into a reasonably dry one over the last four years.

Nick

[cooperlola]

Thank you Nick, very clear and concise.  I wonder what our O/P did in the end.  No response from him I see.

[billyo]

A bit off the topic, but going on ourageous quotes from people who are "in the area", just had a bloke round to quote for air conditioning, he explained everything, took and hour, then spent half an hour on the financing, as in paying it off in installments so the cost in minimal (for the next 15 years) and then set off about the taxrebate situation and how it will only cost half of the actual price. At thispoint i was bored but enjoying the french practice, he then finally got down to giving me a price, by asking me how much I would like to pay for the conroft and tranquility of air con, so finally the price for one unit with two outlets and one oil filled bathroom radiator, 15000 euros. Once I managed to get my chin off the table and stop laughing he spent another half an hour persauding me, using the likes of dropping the price ten percent if he could put an advertising panel up and bring people round to show them the instillation (max 5 people per week in the small print) and leting me speak to a company "director" to show how much of a god deal it was threats of the house falling down due to damp etc. Anyway couldnt get rid of him, tried persauasion that I didnt want it, tried snarling and a bit of aggresion, no good, it finally took my french girlfriend coming home and telling him to stick his quote where the sun dont shine. Despite all that, two follow up calls and an attempt to visit.

Ps just realised I posted this in the wrong place, oops!