Sole plate and post repair questions

[DavidB]

Hello

I am new to the forum and wondered if anyone here can help me with a few questions I have on some repair work I need to do.

My house was built in 1785 and is a grade II listed timber framed building. More recent 'modifications' that I have inherited include internal plaster board and fibre glass insulation between the posts and beams, which have also been painted black. Externally the walls are cement rendered.

I have started to strip out the old shower room which is on the gable end of the house on the ground floor - with a plan to replace it with a new shower room. I had anticipated finding a mess of rotten, damp wood work behind the poor condition shower tiles - I was right!

The sole plate in the corner of the room disappeared up my hoover in a cloud of dust, it was only being held together by the black outer crust of paint. The sole plate on the rear of the house is also in poor condition, but I am hoping to keep this and perhaps add some infill blocks of wood. The sole plate on the gable (side) end that is now missing has been in decay for some years as the cavity shows where cement has been forced into the void perhaps when rendering the outside wall. Just to the right of the missing sole plate is an old door way that has been covered up and here the sole plate has been replaced by cement/brick for a short span before the rest of the gable end sole plate continues (this doesn't look too bad. The plinth walls have been covered in cement and modern paint and the floor has a cement screed.

My current plan of action is as follows, although I would welcome suggestions, and I do have some questions. I've added a picture which I thought might be useful.

1. I'll cut out the remaining cement in the sole plate cavity with an angle grinder and try to make this a square'ish cavity then get an appropriate short section of sole plate and put that in the cavity on a bed of lime. I am not sure how to join this to the cement sole plate - which has a square edge. Perhaps I will use the angle grinder to cut a section out of the cement repair to form a half lap joint. But this leads to my first question - how did they originally secure sole plates to the plinth walls? I can't seem to find any evidence of fixings/pegs in the rest of the house?
2. I am going to try and remove as much of the cement render from the plinth walls that I can without damaging them and re-render in lime. At the moment I am drying them out with a fan heater. I also have a nice breathable clay paint that I will use on those parts of the plinth wall that will remain on display - I've used this elsewhere in the house where I've stripped back the modern paint and it allows the small plinth walls to dry out.
3. I plan to re-attach the posts/studs to the sole plate either with some kind of slip tenon and mortice joint or perhaps a sister post. This leads to another question. If I was to guess I would say the sole plate is oak but I can't tell the difference in woods even when they have leaves on them let alone when they are covered in 200 years of dust, grime and black paint. How do I tell what type of wood the posts and sole beam are made from. I would like to try and source the same material. A further question relating to the posts is should I try and splice a new joint on the end or put a new post in slightly offset to the side and then attach this to the original post perhaps with wooden pegs? As you will see from the photographs the posts are pretty rotten and are quite thin and irregular shaped anyway before the rot set in! So if I was to try and splice them then I'd probably have to cut them back probably by a foot or so. Whereas if I jut left them and put a post next to them and attached the two post further up with pegs then I would be removing less of the original material. But will this be strong enough?
4. Then I'll re-fit a shower cubicle and re-tile etc. So most of this work will be hidden anyway - although I plan on trying to leave an air gap with ventilation around the new shower cubicle - whereas previously it was all sealed off. The room also has a single extraction fan which is nearer to the toilet at the other end of the room - so I think I will also add an extraction fan inside the shower cubicle itself - although this would require making a small hole on the outside of the house for the vent. I will also investigate if there is something else I can do with ducting as an alternative and try to re-use the existing extraction point for both the shower and the rest of the room.

Thanks in advance,
David

 

[livias]

Well I can answer questions 1 and 2

1. Originally it would likely be oak or elm. Elm is not available since they all died and oak is readily available. It is better too, cos it can cope with repeatedly wetting and drying much better than any other native timber. You can recognise oak as it has medullary rays which are paler, slightly wavy lines at right angles to the grain of the timber. However these will not be at all easy to see on a rough old soleplate. For future reference, inspect floorboards or furniture

2. Gravity

 

[DavidB]

Thank you livias that's really helpful - and I'm glad you said 'gravity' for securing the sole plate. Yesterday I stripped back the old cement infill - I thought I'd have to try and cut it out with an angle grinder, but instead I found I was able to chisel it out and I've uncovered some really old wide but low profile bricks under the old cement. So I would rather not have risked damaging them with some kind of fixing.

Can anyone else help me on the post/stud question i.e. should I try and splice a joint on the bottom of the existing posts/studs or would it be better to position a new post next to the original one and join them e.g. wooden pegs (what would you call that a 'sister joint/post')?

I guess from a skill point of view the 'sister post' might be easier for me to do in situ and would require me to strip off the plaster board - not too sure how high to make it and how many pegs to use. Maybe I go the whole height of the room and to the floor boards above and peg it 4 or 5 times i.e. every 2 feet or so? That way I can put a batten on the side of it for the replacement plaster board to attach to. My worry with this approach is will the resulting joint be sufficiently load bearing once everything is in place and secondly will drilling holes for pegs further weaken the existing post.

The splicing a joint on the bottom of the old post might give a more elegant finish, but would be quite tricky due to the location and space and the fact that at least one of the posts is quite thin and irregular shaped. It would also need me to cut away some of the old post to find less rotten wood to form a mortice slot.

Maybe I'll go for the splicing option first and if I make a mess of it or keep having to cut back to find good wood I'll revert to a 'sister post' option.

Last question, should I put any kind of membrane/plastic sheet under the sole plate?

 

[MatthewC]

Last question, should I put any kind of membrane/plastic sheet under the sole plate?

In my view, no, because it will retain dampness and thus ensure that the sole plate is wet for longer than normal; it looks like there is something porous under the sole plate and so it will normally dry out naturally. The plastic might also help transport water straight through the wall...

Matthew

 

[livias]

On my last house I put nothing, but on this one I am employing someone to do the work who is intending to use two staggered layers of lead sheet. He does this sort of job for a living and has done for many years so I will let him have his own way

I can think of two reasons for incorporating a damp course

1. Clients expect it and get twitchy if there is no damp course
2. My last house was built c1480 by a yeoman farmer who of course chose the best bit of land on his farm to place it and it has never suffered from damp in the last 500+ years. I have a friend who owns a house which was built in about 1780 as a farmworker's cottage and was obviously NOT built on the best bit of land as in very wet weather he had a damp kitchen floor. He has replaced concrete with a limecrete and tile floor and inserted a damp course in the walls to protect his decoration. Ten year on, this seems to work fine as a strategy

 

[Me!]

I've seen this done in two slightly different ways, probably depending on how rotten the bottom ends of your vertical posts are.
Assuming a sole plate that is 8" wide and 6" tall.
If the vertical posts are OK, then don't use an 8" x 6" replacement, use two bits of 8" x 3" instead. In the first piece, cut mortises all the way through to match 3" long tenons on the ends of each of the posts. Then slide this new half-height sole plate into the wall and then up onto the tenons (a couple of scissor type car jacks could be handy). Then slide the other bit of 8" x 3" under the first bit and add some pegs from above if you wish to hold them both together.
The second way is a similar idea but involves cutting the rotten bottoms off each of the verticals to the same height, then cutting new tenons on them, then cutting mortises to match in a new bit of 8" x 6". Then jack the new sole plate up onto the posts and finally infill below the sole plate with a few of extra courses of bricks to support it.

However, I can't visualise how you are thinking of using slip tenons, can you explain that in a bit more detail please?

Also, I have a couple of questions please about your clay paint on damp(ish) plinth walls. Does the finish of the paint look patchy depending on the damp patches in the wall behind it, or is it fairly uniform? What make of clay paint did you use please, and would you recommend it?

Thank you.

 

[88v8]

However, I can't visualise how you are thinking of using slip tenons, can you explain that in a bit more detail please?

Chase mortice?
'A Chase mortice (Fig. E) is an ordinary mortice for a stub tenon, but the mortice is continued with a chase so that the rail can be swung round into the mortice. It is used for placing intermediate members into position after the framing has already been fixed. One end of the timber is fixed into postion using a normal stub tenon and then the other end is slid into position along the chase.

http://www.woodworkersuk.co.uk/blog/tips-and-tricks/woodworking-joints-angle-joints-part-3/

Ivor

 

[DavidB]

I've seen this done in two slightly different ways, probably depending on how rotten the bottom ends of your vertical posts are.
Assuming a sole plate that is 8" wide and 6" tall.
If the vertical posts are OK, then don't use an 8" x 6" replacement, use two bits of 8" x 3" instead. In the first piece, cut mortises all the way through to match 3" long tenons on the ends of each of the posts. Then slide this new half-height sole plate into the wall and then up onto the tenons (a couple of scissor type car jacks could be handy). Then slide the other bit of 8" x 3" under the first bit and add some pegs from above if you wish to hold them both together.
The second way is a similar idea but involves cutting the rotten bottoms off each of the verticals to the same height, then cutting new tenons on them, then cutting mortises to match in a new bit of 8" x 6". Then jack the new sole plate up onto the posts and finally infill below the sole plate with a few of extra courses of bricks to support it.

However, I can't visualise how you are thinking of using slip tenons, can you explain that in a bit more detail please?

Also, I have a couple of questions please about your clay paint on damp(ish) plinth walls. Does the finish of the paint look patchy depending on the damp patches in the wall behind it, or is it fairly uniform? What make of clay paint did you use please, and would you recommend it?

Thank you.

 

[DavidB]

Me!,

Sorry my reply to your questions went a little wrong, I'll try again...

Slip tenon\sole plate repair like the one hear: https://www.google.co.uk/url?sa=t&source=web&rct=j&url=http://wam.wychavon.gov.uk/WAM/doc/Plans%2520-%2520incl.%2520OS%2520extracts-697106.pdf%3Fextension%3D.pdf%26id%3D697106%26location%3Dvolume2%26appid%3D1001%26contentType%3Dapplication/pdf%26pageCount%3D1&ved=0ahUKEwiKg77jqvTLAhWHCBoKHQvaDyAQFggbMAA&usg=AFQjCNEN7n07FUMb0Kymgg1PZonYvvThow&sig2=LLpk8YRO_5qgme66fcAX-w

Re claypaint - I only used it on one small plinth wall. It now has one small discoloured patch near the cement floor and the paint has flaked away in one other place. However, before I scraped off the old plastic paint and chipped off some of the cement and patched that with lime render this wall was literally wet all the time even in summer. And previously the paint was flaking off in chunks and looked awful. The wall is now much drier unless it has just rained heavily or very damp outside. I have just checked it and it is bone dry and we've had rain last night - so a big improvement. The paint I used was called 'Earthborn' Claypaint in white matt. It was very expensive - probably about twice what you'd pay for a similar tin from a typical home store. Although that did include delivery. It is lovely stuff to use - like thick double cream.

 

[MatthewC]

The paint I used was called 'Earthborn' Claypaint in white matt. It was very expensive - probably about twice what you'd pay for a similar tin from a typical home store. Although that did include delivery. It is lovely stuff to use - like thick double cream.

Seconded - I used Earthborn clay paint last year for the first time and am very pleased with it - rolling gives the best finish.

 

[Kearn]

After stripping off lovely cement render and concrete infill from the outside of my Tudor cottage, it was apparent that the later brick inserts to the timber frame panels had become somewhat structural over the centuries, as all 7 posts on a 2 bay cottage were floating up to a foot of off where the sole plate would have once been; this having rotted away long over a century ago based on the bricks used to replace it. I employed some specialist help here and we scarfed in replacement lower sections to each post with air dried oak, removing as much wood as necessary from the existing posts to form the receptive joint and then supported underneath with brick.

I can add another nod to Earthborn calypaint - really forgiving to use, just one coat on existing surfaces, and second/third coat touch ups can be done in isolation and it dries so flat that you cannot see the difference. Great stuff!