Water ingress

[jack]

My parents own a cottage, that they bought in 1979. Stone built and they added an L shape to it to increase its size. Originally the cottage was rendered, in their infinite wisdom the render was removed.
This cottage is built with very hard Limestone and lime mortar repointed with OPC mix.

Since then the western wall which is all original has been a problem.
The wind is westerly and so the rain and weather acts on that wall the most.

This wall has a window which I replaced 6 months ago and I forgot to use a waterproofing agent in the mortar mix, so black patches have appeared at the bottom of the window at each ends of the cill on the inside.

Additionally the plaster has developed black or dark patches at various points on the inside of the wall and the plaster was coming away.
The plaster was removed by my nephew using my SDS drill on hammer only with a chisel and most of it has been removed.

There is a cement layer under the plaster which is I assume inner render so offer protection.

They have a plasterer who wiil replaster the inside of this wall.

So my question is will a good waterproofing agent keep the moisture out or not?
And are there any other protection measures that will work?
The tiles on the edge of that part of the roof are the ones with a short amount of tile going over the side of the wall

 

[kebab king]

You really need to find the source of water ingress, sounds like its round the window.Untill then any re plastering is a waste of time really.

 

[Chris W]

agreed... no mention of silicon being used, chances are its getting through the cill...
is it a timber or upvc window? was the cill separate? did you endeavour to introduce any dpc down the jambs when you installed the window?

Additionally the plaster has developed black or dark patches at various points on the inside of the wall and the plaster was coming away. - penetrating damp, and/or condensation


There is a cement layer under the plaster which is I assume inner render so offer protection. seeing as you dont know how hard this is, it might be best to have this off too

They have a plasterer who wiil replaster the inside of this wall. see above

So my question is will a good waterproofing agent keep the moisture out or not? yes, if used in accordance with the instructions AND as part of a waterproofing system where required

And are there any other protection measures that will work? yes, how much have you got to spend? damp diagnosis and solution specification can be a bit hit and miss, there are lots of different treatments for different problems/substrates... it may turn out it just needs to breathe properly...

The tiles on the edge of that part of the roof are the ones with a short amount of tile going over the side of the wall guessing this is a gable end then? further investigation of the verge wouldnt be a bad idea and try the hosepipe test... just hold a runing hosepipe against the wall testing a couple of square metres at a time whilst someone 'spots' the interior looking for ingress

 

[Capital spread]

If the wall is of solid construction built using lime mortar you should not be using sand & cement, any opc pointing should be removed and the wall re rendered using a lime mortar mix The rendering will provide a seal around the window, After the rain the wall will breathe and any moisture will evaporate into the atmosphere.

Due to the walls orientation it will always be a little cold. Any cement on the inside should be removed and a lime mortar render with a lime plaster finish and lime wash applied.
With a cement render /gypsum finish any moisture caused by day to day living will condense on the wall and sit there causing mould.
With the lime mortar finish the wall can breathe and the moisture evaporate.
Has the new window got vents?

If you are still a bit unsure phone your local building control and ask them if you should be using opc on a property built using lime mortar.

Regards
John

 

[jack]

Thank you for your detailed posts.
Whilst the original construction was lime mortar the builder who extended it re-pointed the outside with OPC mix, so it is a mixture.
I agree it should be re-rendered on the outside which would prevent any water ingress but that is not going to happen currently.

The new window is hardwood and I did not use DPC on the jambs and the cill was integral.

The original floor had flagstones which were lifted and then excavated for 6" to give extra height then a concrete floor base was laid and then wood block floor so it is a real mix which is probably the problem.

I am not convinced that re-plastering even with a waterproof inhibitor is going to make any difference.
The inside of the wall has an OPC cement underlayer or inner render and that was applied by the builders 30 years ago.

Stop and think is the best.

As you say half and half lime and OPC bastardises the whole thing, on the one hand it can't breath properly and on the other it is not sealed.

 

[PhilPlaster]

match = insurance = better house

 

[lucius]

Capitol i right the opc pointing if not now will cause you problems sometime or other also removing a flag floor and replacing with concrete with DPM can force any damp if present up the wall