Rising damp

[Knot Competent]

Our 130-year-old cottage has external walls of lumps of granite bedded in mortar, and is rendered externally and plastered internally. There isn't a damp-proof course. We have, of course, got rising damp, which shows as an irregular line on the plaster about three feet above the ground floor level. The plaster below the line is friable, and in poor condition.

My wife wants me to redecorate, so we brought in an expert, who told us the answer was to strip the walls inside and out to a height of three feet, drill loads of holes, inject silicone, and then replaster/render. The estimated cost, coupled with the mental picture of the turmoil involved, brought beads of sweat to my brow and a cry of anguish from my wallet. A near neighbour with a similar problem went through this course of action, with a less-than-perfect result, and his advice was to put up with the damp and save myself thousands. It seems that silicone injection works well on brick construction, but bounces off granite.

Anyone here had experience of this, or can anyone offer advice? Would the use of a dehumidifier solve the problem, or make the situation markedly better?

Regards, John

 

[Noel]

John, I seem to recall that there is (or was) a non invasive system to combat raising damp comprising of a low level current running through a wire around the bottom of the walls of the property. No idea if it was effective. Maybe worth checking out.

Noel, who thought the title of the post may have been about Roper...

 

[johnelliott]

Get a dehumidifier at once. B&Q, Wicks etc. Get a big one if possible. Also, purchase from a garden centre a hygrometer. Hang it on the affected wall, and observe the improvement the dehumidifier will bring about
John

 

[Midnight]

John...

when your house was built, DPC's were a twinkle in someone's eye.. The key to your walls is in the render and plaster; both have to be traditional lime base, as opposed to cement render. Lime mortar never really sets like cement, which is how it maintains its strength (don't ask, I don't understand it either.. just roll with it.. it's simpler). Provided the walls can breathe properly, any moisture drawn up from the ground should be dissipated evenly throughout the walls, the lime base allowing the free exchange of moisture to the air through both the inner and outer face of the wall.
If the render is cement based, it'll be acting as a moisture barrier, not so much keeping the moisture out, as preventing it from escaping. Likewise with any internal plaster that isn't based on a traditional lime mix.
Antiquated they may be, but the old construction methods worked, and will continue to work provided they're maintained with the proper materials. You need to talk to someone more familiar with traditional building methods to remedy your prob...

 

[Scott]

Midnight, you got there just before me!

Let it breathe John, let it breathe man! 8)

I have 150 year old farmhouse with 3 foot thick rubble walls and exactly the same problem. Some dope has plastered the interior walls with modern plaster and, as you say, it's friable and basically falling off. The ground at the back is higher than at the front which doesn't help but you can actually notice the difference in dampness with the amount of rain there has been.

I'm in the process of helping the remaining plaster to fall off and it will be lime-based stuff that goes back on.

 

[Anonymous]

John,

There appears to be a lot of useful information on this site.

http://www.mikewye.co.uk/mikeprices.htm

Howard

 

[tim]

Mike and Scott are on the ball.

Our house has 3 ft thick rubble filled stone walls. Surveyor advised us when before we bought that we had rising damp. Got here stripped anaglypta !!!!! off the walls and had the nuclear proof render shot blasted off the walls outside. NO damp now. Wish we'dknown to do that before we had most of the rooms re plastered. The guy who saved us most money - the plasterer - who refused to only replace the rotten old damp p[laster - told us to wait everything else will be fine. If I saw the surveyor again, I'd kick his a***.

We do also have a thig called Newtonite lath on some wall on the groundfloor which is a vertical dpc to about 3ft - basically to beat any capillary action. But the key is breathability, air movement and as JohnE says a dehumidifier can work wonders as well.

T

 

[frank]

john what you can do to help is dig a drainage ditch around the outside walls just a garden spade width place some roofing slates against the wall and back fill the the hole with gravel this will help the rain water to drain off and keep the base of the wall from getting soaked which will cause your rising damp ,and it wont cost a lot just a bit of graft

hope this helps frank

 

[Knot Competent]

Thanks, guys. This thread has opened up some interesting avenues to explore, but feel free to give a further opinion on any aspect of this. I'm glad that there are others of you living in places of character, rather than breeze block modern shoe boxes.

I'm getting a dehumidifier as soon as possible, and have also been advised to consult the Conservation Officer at the Town Hall (if there is one - the officer, that is!) as he/she should have local knowledge without a commercial bias.

But the strong feeling is the need to replace modern plaster with lime-based plaster, to let the moisture evaporate inside and out. But I am hoping this is only necessary over the lowest three or four feet on the ground floor -- otherwise the cost will be astronomic!

Regards, John

 

[Adam]

john what you can do to help is dig a drainage ditch around the outside walls just a garden spade width place some roofing slates against the wall and back fill the the hole with gravel this will help the rain water to drain off and keep the base of the wall from getting soaked which will cause your rising damp ,and it wont cost a lot just a bit of graft

hope this helps frank

I've seen this advice quoted before, on rec-UK_DIY - it might be worth either searching the archives on google for rec.ukd-i-y (I can't ever rememebr the spelling), as their seem to be several pretty knowledgeable people on their who have made some very comprehensive replies about this subject. I believe that in each case, the drainage ditch around the wall is key to moving moisture away from the outside.

I'll see if I can dig something out on a search... (hang on)....

http://groups.google.co.uk/groups?q=dam ... uk&rnum=10

http://groups.google.co.uk/groups?q=dam ... .gl&rnum=4

http://groups.google.co.uk/groups?q=dam ... net&rnum=5

http://groups.google.co.uk/groups?q=dam ... .uk&rnum=8

http://groups.google.co.uk/groups?q=dam ... uk&rnum=14

Might be of interest anyway.

Also its' worth searching other news groups.

Adam

 

[Knot Competent]

Thanks for all your trouble, Adam. Some interesting stuff there. It seems a gravel-filled trench along the wall is a necessary way to go.

And why am I up at this time of night? Woke up just now in a cold sweat over my current project, an alligator enclosure for a client which needs to be delivered and assembled by the end of next week. SOOOOO many things that could go wrong! And guess what, I've never made anything quite like it before, and in my imagination it keeps blowing up in my face.

I'm sure that in the cold light of day it'll take shape smoothly.

Back to bed, I think.

Regards, John

 

[frank]

john this takes me back about 30 yrs when i first done this for a customer what we used was a waterproofer called madusa (hope thats the right spelling ) you mixed it in with your sand and cement to fix the slates to the base of the wall ,it being a water proofer we had fun trying to wet the mixtur e .( god am i showing my age )

 

[Terry Smart]

Hi guys,

Totally irreverant post to a very interesting thread, just read it all and once again marvel at the amount of knowledge out there just waiting to be tapped...

Just wanted to say...

Wasn't it Rigsby, Noel?

They don't write 'em like that anymore!

Sorry to interupt an interesting topic!

 

[Noel]

"Wasn't it Rigsby, Noel?" Indeed it was Terry. Useless memory.
So who was Roper then?

Noel

 

[Terry Smart]

That'd be George and Mildred Roper, the couple from who had their own series as an offshoot from when they were landlord and lady for a flat in a series called... Man About The House which also spawned another spin-off called Robins Nest.

Wow, I'm starting to wonder if I spent all my early life watching TV... replaced that with a computer monitor now!

 

[Noel]

Thanks Terry, sure we all watched them, but it's the total recall, especially names, that I'm not so sure about......

Noel

 

[Knot Competent]

Wait until you're not sure of your OWN name, Noel!

 

[mudman]

John,

I'd take whatever some dampproofing expert tells you with a pinch of salt. Had to ask them to do surveys before now and comparing notes with others, they all just come along with a damp meter, push it into the walls in a few places and suck in sharply before giving you the hack off to three feet spiel.

We've only ever had old houses and have had damp problems but in all cases ours have been due to condensation from ventilation routes being closed down. Just had a doozy though that turned out to be due to the tank in the loft overflowing and the overflow pipe not being all the way through the wall and running down the cavity wall.


I didn't know about the lime based plaster, I shall file that away for future reference.
Another thing I've read about is people having problems with old houses that have been rendered when they were originally un-rendered or having the rendering removed when it shouldn't be. Sometimes worth checking out what similar houses in your area look like.

 

[RogerS]

I'm not convinced on the dehumidifier route. i thought that they were used to dry something out AFTER the cause of dampness/moisture had been removed/fixed. In the case of an old building with no DPC then there always will be damp rising and I would have thought that the dehumidifier will act like a sponge and just carry on drawing damp and drawing..and drawing. In fact, makes things worse? Just IMHO.

 

[Knot Competent]

I'll let you know, as I'm getting a dehumidifier next week. Can't see that it can make the situation worse, and may improve it considerably. I need to get to a position where I can redecorate the room - it looks terrible at the moment, and I need to take some action short of a total replaster job.

Regards, John