Sole plate concerns

[tobydog]

As you can see from the photo, I've had to carry out some repairs to the corner of our lounge. This part of the wall was always cold and felt damp. It's had a history of 'damp proofing' by the previous owners but I let the warranty expire when I moved in because I didn't want them making an even bigger mess than they already have. Coincidentally, the outside is where an old TV aerial entered the house. Held in place with badly fitting silicone sealant, it never keep the elements out. I have since re-routed the cable through the loft, and closed off and repaired the hole outside properly. Stripping the inner wall of acrylic based paints has now allowed the wall to dry out somewhat. It is gypsum covered limelite in that corner but there has actually been a significant improvement. I opened up the inside as you can see to inspect the damage. I had to remove a small degree of very rotten and loose framing but have since packed it out successfully with a semi dry NHL3.5 / sand mix. Quite pleased with the result and it's probably now stronger than it was.

To see how far the problem had spread, I took the sole plate in the corner back to solid timber by removing an inch or so of the top of the concrete plinth. As expected, I was able to dig out some very loss and rotten (albeit fairly dry) sole plate down to the original slate course. This has now dried out fully and I plan to pack it out again with a semi dry NHL/sand mix.

Given how rotten the bottom of the sole plate is, I know that the concrete plinth in certainly structural. I would like to pack out the entire length as far as possible, doing it in safe stages, however, is this actually quite foolhardy? Should I just pack out the part you can see and leave the rest well alone? I did a similar thing at the other end for about 2ft and that was successful. Interestingly, the sole plate is in two parts and doesn't meet or line up in the middle!

Thanks

 

[Kearn]

Not necessarily scientific or the most help, but when I stripped the exterior of our timber cottage - two bay, 7 posts, 3 load bearing - our sole plate was long gone, replaced with brick and we have various Georgian through later era infill brick panels on the ground floor, which had presumbaly become structural given all 7 posts were effectively floating, some by inches others almost a foot!! We have scarfed in oak to extend the posts, but replacing the sole plate would cause more disruption than it would 'fix'. Whether the post repairs were 'necessary' I couldn't say. Visually it was essential though!

I'm amazed at how little structural integrity is left in our frame, mostly thanks to the Georgians. But that was 300 years ago....

 

[steveb]

we had a skin of structural cement render holding the whole place up - sole plate long gone, most main timbers finished a foot or sometimes 2 short of the ground, those that didn't had the consistency of that stuff that florists use to put flowers in and you could remove with a toothbrush...

 

[tobydog]

You guys are actually making my sole plate sound in pretty good nick. Despite its looks, there is some pretty good structural integrity behind the rot.

Our studs are an interesting mix. Some are solid and sound. A couple have had their feet fixed years ago by bolting on lower sections. Some are at alarming angles and some are old elm that has the same consistency as steveb's flower oasis. One of them just looks like a fallen tree branch! Despite being cement rendered on the outside, the wattle and daub in-fills are long gone and replaced by lovely loft insulation. The internal gypsum panels look very nicely fitted but thankfully there are large gaps at the top where they disappear above the ceiling line which mean the studs and top of the sole plate are pretty well ventilated. There are no obvious signs of the sole plate rolling over as a result excessive outer edge rot but that could be the cement holding it up!

In the old kitchen I have actually removed the whole cement plinth render and rebuilt the 10ft wall under the sole plate. It was an awkward shape that I had to build up with brick and tile. An oddity was that about 2ft of the sole plate was supported underneath by a cast iron brace. All lime rendered back in place. Just nervous about doing the 25ft of lounge.

 

[Kearn]

You guys are actually making my sole plate sound in pretty good nick. Despite its looks, there is some pretty good structural integrity behind the rot.

There was a significant amount of structural over engineering in the cross section of oak used, especially for the earlier properties. Very hard to tell, but your image doesn't immediately look terrible. All depends on how much of the surface is shot Vs what remains sound...

 

[MikeG]

Blimey, that's just about the soundest sole plate I've ever seen, on the face of it. Here's mine:

What's the detail outside?

 

[MikeG]

Duplicate removed. Time to buy a new mouse.

 

[tobydog]

Mike - that's some seriously impressive rot. Things like that help make the decision tree much smaller.

We are cement rendered on the outside but my exploratory excavations suggest it's not having as big an impact as it could have. There is only badly fitting loft insulation behind so the studs are pretty well self ventilated. I would rather replace all the internal plinth render with lime as I have in the old kitchen because, even with cement render outside, this has a huge beneficial impact on the drying out process. Trouble is, as I've found out, the cement render on the plinth is very thick and very structural.

As for the condition of the sole plate, I would guess that it's similar throughout it whole length even though I've only exposed 1ft of it at that end. My concern was that, knowing where the original slate damp course now sits in the void, about 60% of the sole plate is probably sponge!

 

[MikeG]

Hmmm.......

Toby, I would argue that the render on the outside is far more important than whatever is on the inside face of the wall. People always have the misconception that outside is damp and inside is dry, but the reality is that most of the time it is very much the other way around. I don't get het up about gypsum plaster on the inside of an external wall, because it is something of a vapour barrier preventing the damp from the house getting into the structure. This is a controversial view here, but the fact is, the inside of a house holds warmer air than the outside, much of the time, and warm air holds more moisture than cold air. Also, we are constantly producing moisture inside our houses*. Moisture entering a wall will then condense on a cold surface.....the inside of the outside wall covering, particularly if it is impermeable. It then runs down the inside of the render until it reaches something to block its path, which is generally a brace or plate. There it sits and rots the timber. Frankly, I wouldn't pay any great attention to the inside of your walls until you have removed the sand & cement render from the outside, and rerendered with lime. Ideally, if you aren't listed and if the plinth details allow it, you could put a breather membrane over the outside of the frame whilst it is stripped, then batten out to form a small void, then re-render. That way your timber frame will be immensely safer from the effects of interstitial condensation, or from the ingress of water from the outside, compared with how it is at the moment.

Arguably by lowering the resistance of the inside face of the wall to the ingress of water vapour but retaining the outside in the same state it is now, far from drying out your wall you will actually be exacerbating the problem.


*As we know, the best answer to damp is ventilation, and the place with the most ventilation, by a factor of squillions, is outside.

 

[MikeG]

........ knowing where the original slate damp course now sits in the void, about 60% of the sole plate is probably sponge!

Following on from my previous, I doubt the slate DPC has much bearing on the condition of your sole plate, so long as the plinth is more than 2 or 3 bricks high. The biggest killer of sole plates on plinths isn't damp rising from the plinth, but moisture that penetrates the wall above and condenses on the inside of the render before running down to sit on the horizontal and diagonal timbers. If you have sand & cement render everywhere externally, then I wouldn't be anywhere near so confident as you are that the sole plate was sound.

PS.......I note your location, Toby. I am in south Suffolk too. If you want me to come and have a quick look (gratis, of course) I'd be pleased to.

 

[tobydog]

Mike - unfortunately replacing the outside render is not an option. The cost would be too much, especially as I do know it would lead to further structural work. The outside of our house has to be seen to be believed. I'll take some photos at the weekend but try and imagine cement render coming down the front wall of the house and continuing, without a break, 3ft or more into the ground :shock: . We were able to talk with the old couple who 'renovated' the house in the early 90's. They asked the builder how they could protect the plinth from rain coming off the thatch. That was his solution. Removing the cement render is a last resort.

Left with a plinth having cement render on both sides with the sole plate on top, I had no option but to start removing it from the inside. I started in the old kitchen and soon realised the damage underneath. I removed the badly damaged and crumbling bricks, and a considerable amount of rotten wood that was just like compost. After taking the sole plate back to solid wood I left it all to dry out for several months. Rebuilt with brick, tile and lime mortar, I left it again for several months and the plinth remained bone dry. I then rendered with a lime putty mix and it's been happy times since. I've done this on two sides and the other side of the other wall is still dry as a bone. It too was very damp. I know it's dry because I opened up the other side where the cloak room is and left the plinth open to the room.

When we moved into our house in 2009 we had considerable condensation on our windows every winter morning. Since drying out the plinths, stripping the significant cement render for the back of the inglenook and recoating in lime, our house has dried out really well. We have no mould anywhere and no where does it smell of damp (except for one place which will be another post) even in the middle of winter with the windows shut. I should add that we also have solid concrete floors throughout the ground floor which was further reason to expose and correct the plinths.

 

[tobydog]

Mike - I was going to suggest maybe meeting up. I'm about 7 miles south of Ipswich. I will send you a PM if I can remember how. Thanks

 

[CliffordPope]

warm air holds more moisture than cold air.

Can hold more moisture than cold air.
It doesn't follow that if rain is driving against the house in a howling gale, it will be even wetter inside

 

[88v8]

Our eastern soleplate was internally plasterboarded/gypsumed. The plasterboard got damaged when we moved in, and poking about I found the elm soleplate wet and soft, could easily get a knife in it an inch or more.
Took off the plasterboard and lime pointed the wall below, which is the flank of the cellar staircase.
Now the sole plate is dry and hard. So that was a lucky win.

Much of our external timber infill is cement, some wattle & daub. There are some sizeable old resin repairs in the frame. Like Toby, I am reluctant to get into it, as I know it would lead to a lot of woodwork that I don't want to do. Especially given that the lower floor is the kitchen. Luckily the half-timbered wing is on the north side and thus doesn't get much weather.
Don't think I'd have the appetite for a major operation like Mike's. Perhaps at one time, but now it's likely to be left for a future owner.

Render... at Lacock last year we saw some old pics, back to late C19, street scenes with many timbered buildings whose facades were completely rendered over and looked as if they had been built that way. Lime render of course.
I wonder how much of our timber frame troubles are due to a historic failure to maintain the original render, and then it being stripped in a process of prettification where the frame was never designed to be exposed to the weather.

Ivor

https://www.nationaltrust.org.uk/lacock-abbey-fox-talbot-museum-and-village/lists/the-fox-talbot-museum-at-lacock

 

[MikeG]

........Render... at Lacock last year we saw some old pics, back to late C19, street scenes with many timbered buildings whose facades were completely rendered over and looked as if they had been built that way. Lime render of course.
I wonder how much of our timber frame troubles are due to a historic failure to maintain the original render, and then it being stripped in a process of prettification where the frame was never designed to be exposed to the weather.......

Absolutely. This is hugely important. Of course, it wasn't that all timber framing was rendered over externally, far from it. But much was.

 

[tobydog]

Yes, buildings like the Guildhall in Lavenham were never rendered over in the first place because the owners wanted to show off the impressive framing and how wealthy they were. Our frame is a combination of old ships, older houses, and what looks like any big branches they found in the woods. I guess ours would have been rendered over from the outset with a more appropriate covering.