External Render and or Limewash to conquer water ingress

[Mickey]

Hi All,

Hoping for some advice, we are about seek CO advise to finally sort out the continued water ingress through the rubble filled walls - as far as I can see it we have 3 options for external works 1. slate hanging....I'd be very surprised (but delighted!) if our CO would support this, 2. lime render followed by limewash 3. just limewash.

Has anyone any experience of the efficacy of render and limewash or just limewash for preventing water ingress. I am not sure of the weather proof properties of limewash for wind blown water penetration I'm presuming that adding linseed oil to the limewash would make it more waterproff but still breathable but could result in bad mould growth which wouldn't be great on the front of the building. Any advice gratefully received. The walls are made of inferior stone and despite having redone lime pointing outside and lime rendering inside it's still letting in water!

many thanks
Mickey

 

[88v8]

Sorry to read about this.

The search 'water penetration historic building Scotland' throws up a lot of hits, and page-foot links.
I chose Scotland because the Scots tend to be wet.

Perhaps you could pick a damp day, settle down with a good glass or bottle of malt, and do some reading. Although I guess you have already done so.
Render, weatherboarding, pentice boards, tile hanging, water repellants, limewash.
I think limewash alone would be pretty useless, as it rapidly saturates.

I have not read deeply on the topic, but water repellants seem to be of variable and dubious value
http://www2.rgu.ac.uk/schools/mcrg/miconsol.htm

and I can understand that your CO may have problems with the more effective solutions of hanging or boarding, in view of the appearance change.

I think I would go for Keim Granital
http://www.keimpaints.co.uk/fileadmin/uk/pdf/Lime_Render___Why_Buildings_Need_to_Breathe.pdf
initially applied to the stone for which I would not seek CO's permission, but if that fails, applied to a lime render, which changes the appearance so now we are back to the CO.
The CO should be sympathetic to your cause, as damp is bad for the building and the occupants.

I wonder how long the water has been coming into your house? Perhaps previous occupants tried and failed to combat the problem?

Ivor

 

[DavidB]

Mickey

My understanding is that lime mortar, render and limewash all allow moisture to penetrate and soak into the wall. The wall then releases this moisture and dries out. This process results in weathering and hence why lime rendered surfaces need to be maintained i.e. re-pointing, new layers of limewash applied and indeed re-plastered. How much the water soaks into the wall i.e. the depth and then the speed at which it then dries out depend on a number of factors including the surface finish (closed or open style of floating the lime render), weather factors such as driven rain etc. This soaking and drying out is part of the design feature of the older house.

I think you should expect some soaking and absorption of water. In my house, previous owners have tried to make the house 'water-tight' and coat the lime in non-porous materials such as cement and plastic masonry paint. This has caused a secondary problem that the building was not designed to deal with. The non-porous materials are not as flexible as the lime plaster and the wooden frame flexes due to changes in temperature. This movement has resulted in some small cracks. These cracks can then allow water to run into the fabric of the building. The water doesn't evaporate as efficiently and the moisture gets trapped and causes rot to wooden frames and/or blown plaster.

You describe your problem as 'water ingress' - if it's coming in through cracks in the pointing/render - then those problems should be addressed i.e. re-pointing, re-plastering and limewash. If it's soaking in - then you may not need worry too much and instead try to encourage the drying out phase of the process that the house was designed to exploit. Examples of how you might encourage drying out include:
1. Check external floor levels (have pavers being laid on top of outside floor covering - raising the floor and reducing evaporation at ground level).
2. Are external floor surfaces causing rain water to bounce back up and splash the wall instead of soaking away in the ground (i.e. have pavers been laid too close to the house)
3. Remove plants and shrubs that are close to the wall surface i.e. allow air to circulate
4. Check wall finishes are appropriate and remove if they are not

You may also find other factors that contribute to the water ingress that need to be stamped on before they cause damage i.e. any leaking drainpipes, guttering etc. These need to be repaired asap - bacause if they are allowed to continue to work inefficiently they concentrate leaking water in one particular area and overload the wall with water.

I find YouTube a good source of advice on these topics and someone like Peter Ward has many videos and if you search his channel you may find a house like yours.

 

[Mickey]

Many thanks both for your helpful replies, mineral paint might be the way to go but I am not totally convinced that any single layers of paint is going to hold back rain (especially since they claim it is breathable which I remain sceptical re how can it allow water to bead whilst still being breathable?!) which hits the building at 50+mph during some of the storms we get. To put this into context the wall is/was rubble filled construction but decades of weather have in all probability washed out some of the in fill causing voids and loss of substance to the wall and hindering it's ability to deal with the amount of rain we get here. CO has been a very sympathetic has gone away to deliberate on course of action so we'll just have to wait and see. There are no ground levels which are higher than the internal floors, floors are board with 3 foot voids underneath and plenty of air vents all round and rain water goods all ok, wish it was that simple

Thanks again

 

[Me!]

especially since they claim it is breathable which I remain sceptical re how can it allow water to bead whilst still being breathable?!

Generally this is done at a molecular level. Water vapour has molecules that are basically free to move around individually, whereas water liquid has molecules that are attracted to each other with sufficient force to stop them drifting apart. So if the paint has holes in it that just are big enough to let individual water molecules through then it is breathable, and if those holes are not big enough to let several molecules through at the same time when they are all holding on to each other in a liquid form, then it is waterproof.

If you try a Goretex coat, that works the same way. Rain drops run off the outer surface (even in a 50mph storm), but you don't get hot and sweaty inside as moisture from your skin can still evaporate and go out through the breathable membrane.

 

[Tony.]

Mickey,

Can you advise on where the water ingress appears on the inside?

What is the relationship between this water ingress and say all the exterior rainwater goods, chimney etc.
Just in case this is the source rather than through poorly maintained walls