Grade II Listed cottage with leaky wall

[greyknight]

Hi folks

 

First post so thanks for letting me in.

 

I recently moved in to a 17th century grade II listed timber frame cottage and over the past couple of months I've been having problems with one of the gable end walls leaking quite badly when it rains.

 

The wall is south west facing so takes the battering of the elements most of the time. The timbers are also exposed both outside and inside. The previous owners have had some work done and a number of rotten timbers have been replaced and the infill panels towards the top of the frame have been replaced with lightweight materials to prevent further stress on the frame, all good.  However, the lower infill panels are brick and it seems to be these that are leaking badly around the edges when it rains, water seeps in under the timbers and runs down the interior wall causing staining and large damp patches.  It dries out again when the rain stops, but I can't carry on with ugly interior walls covered in streaks and mould.

 

I've read and watched a lot of materials on how to look after old houses like this and because it's a listed building I know I have to use traditional materials to do any repairs.  My main question is how should i go about waterproofing around the edges of these leaking infill panels?  I've already ground out some of the old mortar around the edges of a couple of the panels and hammered in some shipbuilders oakum (tar soaked fibre) which is a well documented method, but I'm not fully convinced about the results.

 

What I'd really like to find is a person who has experience of timber frame houses to advise me, I don't seem to be able to find a local specialist and I don't trust just any old builder to understand the importance of using the correct materials and methods. 

 

So, the main question, how do you get a good watertight seal between timber and brick without using cement mortar?

 

thanks

 

Graham

[Cpd]

1 hour ago, greyknight said:

What I'd really like to find is a person who has experience of timber frame houses to advise me, I don't seem to be able to find a local specialist and I don't trust just any old builder to understand the importance of using the correct materials and methods. 

Absolutely no idea what what the solution to your problem is but if nobody can help you here then try the green building forum https://www.greenbuildingforum.co.uk/

[Big Jimbo]

I like the idea of your tar soaked rope. On a logical basis, the bricks won't move, but seasonally, the timber will, so you will always get cracks between the two.

[Temp]

I think tar and rope is used for boats. Sounded good to me as well but unfortunately this place says tar can trap water causing the wood to rot.

 

https://www.heritage-house.org/stuff-about-old-buildings/timber-framed-buildings/oak-frame-construction-and-repair.html

 

They suggest..

 

We have 'Maintenance Packs' available to purchase - these consist of small bales of oakum caulking, specially manufactured and imported from Sweden where it is made for use on wooden sailing ships.  This is twisted into narrow ropes to fit the size of any gaps in the frame, and then hammered into place.  Lime mortar or putty is then applied over the surface of the finished caulking to protect it.  Oakum is flexible, waterproof, and most importantly, breathable.  It will not trap water against the frame.  A caulking iron is an optional extra - they are a beautiful tool, a work of art in themselves, and are made to tighten the oakum in narrow gaps, leaving a slight ridge on the surface which sticks to the lime putty covering it.

 

 

Edited February 21, 2020 by Temp

[Mr Punter]

If it is just that wall, would it be out of the question to clad it?  Could use oak, clay tiles or natural slate?

[Jeremy Harris]

I wonder if the original lime mortar may have been replaced with cement-based mortar during some of the earlier repairs?  Lime mortar has a degree of flexibility that cement-based mortar doesn't, so might be more able to tolerate a bit of movement.

[jfb]

I would mix up a dryish hydraulic lime/sand mortar and point that in having taken out any  existing loose mortar. Finish with limewash to match existing. As Jeremy asks - do you know if the existing brick infill panels have the original lime mortar? And is the paint a limewash or a more modern paint that might not be breathable?

[greyknight]

3 hours ago, Temp said:

I think tar and rope is used for boats. Sounded good to me as well but unfortunately this place says tar can trap water causing the wood to rot.

 

https://www.heritage-house.org/stuff-about-old-buildings/timber-framed-buildings/oak-frame-construction-and-repair.html

 

They suggest..

 

 

 

 

 

Thanks, yes that oakum stuff is exactly what I'm using.  It's soaked in stockholme tar but is fully breathable.

 

I don't know whether the mortar that's in there is lime or not to be honest, but the stuff I'm putting in definitely is, though I'm using non-hydraulic lime as that's what you are supposed to use for old properties.  I'm not convinced that pointing alone will stop the leaks though because lime mortar is permeable so water just soaks through it like a sponge.

 

Yes I'm going to lime wash it afterwards, but this is all a summer job really as you aren't supposed to use lime mortar in cold temperatures.

[mm289]

Couple of thoughts...

 

Just on terminology, you are probably well up to speed on this but just incase?. Two limes to be used on older buildings are Natural Hydraulic Lime (NHL) and non-hydraulic lime (unhelpfully can also abbreviate to nhl) but is ususally only supplied as Lime Putty. The lime NOT to use is hydrated lime sold at builders merchants and often added as a plasticiser to cement.

 

Lime putty has a softer set than NHL and is more suited to timber frame that reuqire a lot of moevement. The problem with putty is it has a loooong set time as it goes off by reacting/reaquiring CO2 from the air. In a wet environment and this time of year it won't go off for ages if at all so probs won't make any impact on your damp issues. NHL on the other hand will go off in wet conditions.

 

I have used lime (NHL in my case) to fill around gaps on window frames and it copes reasonably well from a porousity pov. It doesn't allow water to stream through, it may look a little damp if you have clay paint on it but this dries out quickly.

 

I can see the logic for the oakum, if you were ramming that into gaps I would be inclined to point over the top with lime and would expect this to stop most of the water ingress, certainly to the degree where you didn't have visible wetness on the inside of the wall.

 

I would also be looking closely at your timbers, how wet are they, is there any treatment on the outside, it looks like there has been but this has worn away. Maybe check them with a damp meter compared to the wall to check they are not allowing the water to come through?

 

Final thought, you will be surprised how long it takes a wall to dry out. Even if you did all the remedial work I reckon it would take 6 months through summer before your wall dried out properly, so in reality anything you do know is prepping for next winter?

 

Oh, and assuming you have done all the other stuff, checked for leaking gutters, made sure soil height isn't to high against wall, gradient of outside allows water to run away from wall not into etc etc.

 

HTH

 

Paul.

[greyknight]

1 hour ago, mm289 said:

Couple of thoughts...

 

Just on terminology, you are probably well up to speed on this but just incase?. Two limes to be used on older buildings are Natural Hydraulic Lime (NHL) and non-hydraulic lime (unhelpfully can also abbreviate to nhl) but is ususally only supplied as Lime Putty. The lime NOT to use is hydrated lime sold at builders merchants and often added as a plasticiser to cement.

 

Lime putty has a softer set than NHL and is more suited to timber frame that reuqire a lot of moevement. The problem with putty is it has a loooong set time as it goes off by reacting/reaquiring CO2 from the air. In a wet environment and this time of year it won't go off for ages if at all so probs won't make any impact on your damp issues. NHL on the other hand will go off in wet conditions.

 

I have used lime (NHL in my case) to fill around gaps on window frames and it copes reasonably well from a porousity pov. It doesn't allow water to stream through, it may look a little damp if you have clay paint on it but this dries out quickly.

 

I can see the logic for the oakum, if you were ramming that into gaps I would be inclined to point over the top with lime and would expect this to stop most of the water ingress, certainly to the degree where you didn't have visible wetness on the inside of the wall.

 

I would also be looking closely at your timbers, how wet are they, is there any treatment on the outside, it looks like there has been but this has worn away. Maybe check them with a damp meter compared to the wall to check they are not allowing the water to come through?

 

Final thought, you will be surprised how long it takes a wall to dry out. Even if you did all the remedial work I reckon it would take 6 months through summer before your wall dried out properly, so in reality anything you do know is prepping for next winter?

 

Oh, and assuming you have done all the other stuff, checked for leaking gutters, made sure soil height isn't to high against wall, gradient of outside allows water to run away from wall not into etc etc.

 

HTH

 

Paul.

 

Hi Paul, thanks for taking the time to write that, I broadly agree with all your comments.

 

So I have a tub of NHL putty which I mix with sand to make mortar, 1 part putty to 2 parts sand.  I'm not very good at pointing yet so need to practice that.  The issue I've had is that the small amount of pointing I've already done has cracked when drying so I probably need to pull it out and do it again, but try to keep it damp as it dries.

 

I think being only 1 brick thick the walls will dry fairly quickly and the timbers seem okay to me.  I'm wary about using a damp meter because research has shown they are next to useless and shouldn't be relied upon.

 

There is no issue with outside ground levels, mainly from the point of view that the house is built on a dwarf wall so the lowest timbers are 18" above the floor.

 

When you say you have used lime around your windows, do you mean raw lime putty, or mixed with sand to make mortar?  How wide a gap do you think you can fill just with the putty on its own?

 

There's definitely no problem with rising damp, it's literally just rainwater ingress from top down that's the issue here.

 

Thanks

 

Graham

Edited February 22, 2020 by greyknight

[mm289]

My gaps were smallish probs no more than 1/2" - and yes it was lime mortar

 

1:2 is quite a stroing lime mix, more often see people using 1:3 in my experience. Also what sort of sand are you using? Needs to be sharp not builders and a little course as this give the mortar some strength. WOuld be surprised if your mortar was drying out too quickly in this weather ? - unless you are meaning historically

 

Definately wouldn't use putty on its own as without sand there is no binder so the putty will just crack.

 

Cheers,

 

Paul.

Edited February 22, 2020 by mm289