Water ingress problem

[Keithj]

We had rain worthy of old Noah this weekend. The wind was from the south west, and strong. Water was coming into the dining room and making healthy sized puddles on the floor.

We've paid lots of cash to a specialist builder to fix the problems with the house, so we're not best pleased that it's leaking. He's coming back tomorrow, and we will discuss with him the problem and solutions. But before going into the haggle, I'd appreciate the views of the assembled wise folks here.

The south gable wall is a bit of a "kludge" because the floor joists/beams were slightly too short to rest properly on the end beam. The previous beam was rotten, and the joists held up only "by art". The water ingress problem was serious.

This is the arrangement now:

The oak beam is new, as is most of the wall structure. There is an additional beam "inboard" of it to support the bedroom floor/dining room ceiling. Below that are the window frames. Above is lath and lime/chalk render on the outside, and plasterboard/skim on the inside. The gap is insulated with wool.

The lime render on the outside stops about half an inch inboard of the oak beam, so there is a small shelf on which water can collect.

I think water is collecting on this shelf, driven towards the wall by the wind, and then percolating under the render. There is a paper-thin gap where the render has dried/carbonated and the green oak has shrunk slightly.

When the rain was heavy, we had a stream (not drips) of water running from the beam, down the window frame, and onto the floor. I can't think of any other plausible reason for this.

My non-expert solution would be to get the lime renderers back to add a fillet to the render, taking it outboard of the oak beam, like this:

My theory is that the fillet will stop water collecting on the shelf and being driven into the house.
Is that a valid theory and the right solution to the problem?

Next question: there are similar "shelves" elsewhere around the house where lime render meets sole plates etc. Should they all have such fillets?

 

[Pford75]

I suspect that our solution is not authentic or perhaps even ideal, but it functions well enough. We have a similar (but not identical) situation where a second story was built many moons ago on top of a single story, except in our case it is a brick wall on top of a clay lump wall. The upper wall has lead flashing chased into a mortar joint and this then overlaps the lower 'proud' wall preventing water from collecting.

 

[MatthewC]

Would the gable once have had thicker render (or the laths further out from the wall) so that the external surface was flush with the oak? Or if not, assuming your new oak beam is exactly the same size as it used to be, then it would have also previously suffered the same water ingress which would probably be why the previous beam rotted.

Logically, your proposal of a mortar fillet looks like a good idea as a ledge like that cannot be right. Another possibility would be to cut a bevel on the upper exterior corner of the oak, so that water runs down the outside of the oak, but that might not be a traditional solution and could look worse, I suppose.

 

[MdB]

As I was reading and viewed your first picture, my thought was a lime fillet as you suggested in your second picture. My one worry would be getting a good joint with the current lime finish as you would want to avoid getting a crack between the old and new which would collect water.

 

[Keithj]

The builder is coming this afternoon to take a look for himself. Talking to the plasterer (who does lime work also) his view was that the lime should be hacked out back to the scratch coat, up as high as the fillet goes. That, he thinks, will provide a strong enough bond.

The alternative is to cut in a lead cap, but that's a lot of lead, a lot of cutting, and probably far more work than a lime fillet. It would still need lime mortar to fix it in place.

I've looked (now ) at the render that wasn't disturbed during the repairs, and realise that a) it's much closer to the outer edge of the plates and studs, and b) has a fillet such as I described above. There are lots of questions in my mind around "why did you do it like that?"

The learning curve with this house is amazing!

 

[middi]

This is a typical example where traditional buildings in it's pure form are not really suitable for our contemporary expectations of modern living. Unfortunately the builder did not allow for the fact that the particular Oak beam would continue to shrink for the next 5 or 10 years therefore creating a gaping clearance between the oak face and the abutting fabric. As the oak face is protruding beyond the elevation this would duplicate a problem wich would manifested itself in the years to come.
Two or three centuries ago this kind of approach to building was quite normal, the owners or keepers were expected to infill the gaps and maintain a " reasonable" wetherproof seal and quite acceptable to have ongoing maintenance. The only mistake your builder has done was that he/she did not allow for the fact that this kind of construction and maintenance burden is not acceptable to modern day " man".
I would have incorporated a breatheable membrane under the laths and dressed a small strip of ( isolated) lead under the membrane and lipped just over the oak ledge. This woukld have taken care of the shrinkage problem of the oak therefore eliminating any possibility of leaks.

Middi