Water ingress windmill restoration

[Teresa wells]

We have had extensive brick and mortar repair work with timber lintels replaced to our grade 2 listed windmill. We are still getting water ingress around the tops of the windows between lintel and brick. Can anyone suggest what has happened . It has been
Painted with Keim royale breathable paint .

 

[Cubist]

The most logical cause, assuming new timber lintels were installed, is that these have 'shrunk' since they were installed and a fissure has opened between the top face of the lintel and the brickwork. The fix is straight forward enough - depending on height and access.

 

[Teresa wells]

Thanks any suggestions of how to fix this bearing in mind lime plaster has been applied to inside. We can’t see any visible shrinkage . They were also cut back to the face of the brick .

 

[Cubist]

This problem is best treated from outside the building as the remedy is to apply suitable caulking materials to close the gap between the upper face of the lintel and the brickwork, thus blocking further rainwater ingress. I would stress that this needs to be done properly to ensure a lasting solution. Have you the necessary equipment to reach and work on all the affected windows yourself or would you need to employ a contractor?

 

[Cubist]

A rapid after-thought. You say that the lintels were cut flush to the brickwork, was this done for the internal faces only? If the lintels protrude beyond the brickwork on the exterior then this will form a shelf upon which rainwater running off the face of the brickwork above can collect and then be driven over the top surface of the lintel by high winds. If this is the case, and once a fibre caulk has been inserted into the crevice, a sloping fillet of mortar or similar may also be needed to encourage more efficient run-off.

 

[Teresa wells]

Lintels are cut flush thanks for asking. Can I ask what is your experience - we have been let down on this project. We can reach the lintels with a cherry picker and would prefer to try and fix ourselves. The architect thought it was water in the brick absorbed by the vast amount of lime plaster applied internally. However plasterer doesn’t think so. It’s such a worry as no one can give a straight answer. It didn’t leak before new lintels were fitted and it was in a bad state .

 

[malcolm]

Can you post a photo of the lintel from the outside? Also is the water ingress in the form of damp or is it liquid dripping in?

We had a waterfall from a lintel in the farmhouse. I think it was because a gap had opened up after the wood had shrunk. Wood does shrink a lot over the first couple of years then becomes more dimensionally stable.

 

[Teresa wells]

It’s water dripping in - especially when it’s raining hard .

 

[Teresa wells]

We can’t see any gaps that’s the wipers thing

 

[Teresa wells]

Weird

 

[malcolm]

We couldn't see the gaps in ours either. A flatmate found where the water was getting in using a hose pipe. Starting low and slowly working upwards with someone inside watching for leaks.

 

[Cubist]

Hi Teresa,
Yours is the safest assumption and I think you're right that rainwater is being driven in over the top of the lintels. This is a common problem with timber frame properties such as ours, and others that use timber lintels exposed to the external environment. The fundamental issue is that heavy timbers such as these are constantly moving and, depending on their unique internal grain structures, that movement can be disproportionate to the original cut dimensions and and have little or no uniformity. As a consequence its is vital that flexible materials are used as an interface between the timbers and any surrounding brickwork/other materials including wood.

I'm guessing but I suspect that whoever installed your lintels may have simply pushed in a fillet of mortar between the top face of the lintel and the brickwork above. This frankly is a near fatal mistake as that ribbon of mortar will be repeatedly compressed and de-compressed by the pressures exerted by the wood as it expands and contracts and will fail its purpose almost immediately.

In terms of how to fix the problem;

Fortunately it seems we may be heading into some drier weather and you have access to suitable access equipment. for each of the lintels I would suggest that you : -

1. Remove the ribbon of mortar (whatever) above and on the sides of the each lintel to a depth of 15-25mm removing any loose material.
2. Assuming the resulting gap between the top edge the lintel and the brickwork is as narrow as it should be then twined caulking cotton should be pressed firmly into the cavity and packed idown to about 5-10mm below the surface level of the lintel/brickwork.
   1. Caulking cotton is sold on-line by marine chandlers in rope form and costs about a £10 for all you're likely to need. This can be twisted and pulled to make the rope thinner to fit tighter spaces or braided to make it thicker to fit snugly into wider gaps.
   2. Ideally you will want the final fit into the cavity to be sufficient to resist gently efforts to pull it back out.
3. Given your situation I would then advise that you use plumbers putty, unlike glazers putty this does not set and will therefore not break up and fall out, to fill the crevice above and on the sides of the lintel and if need be create a sloping fillet from the brickwork to the leading edge of the lintel face rather like that used for windows.

This should be more than enough to prevent future water ingress from this source and the materials should not cost more than £20-30.

Ordinarily I would not suggest plumbers putty but this will retain its flexibility and adhesion to all the surrounding surface and will, after a few months, gather sufficient surface tension to allow it to be painted should you want to.

Please do not be tempted to use a silicon type sealant, all such ultimately fail and can permit/promote incredible damage to the timber.

Hope this helps and happy to offer more if I can.

Good luck,
Cubist

 

[Teresa wells]

Thank you and fingers crossed for fine weather . Will let you know the result .

 

[Cubist]

Thank you and fingers crossed for fine weather . Will let you know the result .

Please do.

Sounds like you have a fascinating project there and I'm sorry to hear that your builders have/may have let you down. There are many members here who have relevant and hard won experience that may be of help and are happy to share. On a personal note the First Lady and I ran away from a windmill during the early days of the hunt that culminated here but that was an almost total re-build project for which we just did not have the time - but we hummed and harred over that decision for quite a while afterwards, and there are still moments of regret.

 

[Cubist]

One thing I forgot to mention. Theres a possibility that having shrunk the recent wet weather may cause the lintels to expand again and it may appear that the problem has sorted itself out. Don't be conned by this, a permanent remedy is essential to prevent future damage indoors and to protect the timber itself from rot and beetle infestation due to accumulations of water sitting on its upper surface beneath the brickwork

 

[Teresa wells]

Hi Cubist

Just to let you know we are still having water ingress problems especially in driving rain. All windows have now been caulked and had linseed putty on them. We had the conservation officer round and he suggested that it was water in the brick after many years of being exposed to the elements and that was seeping downards especially during driving rain. I have also just looked at SPAB and they suggest that because the mill is a cone and the walls slope inward that there will always be leaks. Not what I wanted to learn. Funny though how it just leaks above and around the windows and no where else. MMMM! suggestions?

 

[noj]

We've got a little, lead topped, angled strip of wood above our exposed windows which works.

Easy to achieve with weatherboard, but maybe just a suitably angled bit of flashing would function at the top of your lintels?



This one has survived a while, it's still hung on pintles and the casement stays hang down outside.

 

[jamest]

If you've caulked as Cubist suggested and that hasn't solved the problem, then it's possible your CO is correct, in which case you have a really tricky one on your hands. If there is water percolating down inside the wall, then it will meet the lintels and leak out, likely inside as you've found. So what you've got sounds to me like what you might expect given the scenario suggested by the CO. Cracks in the mortar anywhere in the wall above a lintel could contribute and if a wooden lintel has shrunk a bit, that could produce tiny mortar cracks further up the wall, not only in the mortar fillet along the lintel itself. Couple all that with an inward sloping wall and the effects you report would seem almost inevitable. Under no circumstances should you use a waterproof seal on the inside to prevent water ingress - that will simply trap the moisture in the wall and it will rot the lintel and leech out somewhere else. There are lots of converted windmills around, with porous brick walls - how was the problem solved in those cases? Hopefully not by using waterproof sealants on the inside! You can't really waterproof the outside either and lime rendering is likely not an option . . . there are these breathable siloxane based coatings like Silic8 Silguard which is sold by Lime Green, never tried it though and don't know if it would offer a solution, maybe someone else on here knows

 

[Teresa wells]

Thanks - for all your comments - I think a cherry picker in order and a closer inspection higher up.