Sill plate replacement

[xanthe]

Has anyone got experience with replacing sill plates - especially those which are now below ground level?

All the sill plates on the new property are below the outside ground level. There is a cellar beneath the house and the plates are still there, but wasn't possible to reach them in order to find out what state they are in. Visually they didn't look too bad but that might be an illusion.

The timber frame on the ground floor on front and gable elevations has totally gone - whether the timbers rotted or were removed when previous owners were mucking about putting doors and windows in and out I don't know, but we suspect the former or a combination.

I'm going to get a structural engineer in to see what is going on, but am trying to research what I can in advance so that I can ask vaguely intelligent questions and prepare for the worst!

I am assuming that if it's totally gone then the house would need to be jacked up in order to put a new one in? If so, does that require taking the brick infill out on the ground floor to do this? Or can they be fixed from below - there's no brick plinth, the beams are resting on the sandstone type blocks of stone that the cellar is made of, so would be difficult to get to from underneath.

Have looked about online, but everyone with rotten sill plates appears to have them above ground.

 

[malcolm]

I'm not sure I'd replace it with wood if it is underground - won't it just rot again? I'd be inclined to replace it with bricks. That ought to be a lot easier - support whatever is above with acro props, remove a small section of rotten beam and replace with bricks.

Not sure a structural engineer is a good idea unless you want to alter the structure. They have a tendency to charge £500/hour to tell you that the whole house needs underpinning and a steel frame inserting to hold it up. Also they can't see what's hidden any better than you can. Old timber framed houses can settle a lot but don't seem to fall down often. If you want to leave it as existing and just work out how to fix it maybe a Conservation Surveyor or a good restoration builder might offer advice.

 

[xanthe]

Thanks Malcolm. I am wondering whether there is a possibility that the house has just settled, potentially rotten plates or not, and will be fine as is, given that the plates have been underground for at least 100 years already.

The nice chap at SPAB has recommended a structural engineer in the area who specialises in conservation and timber-framed buildings so I am hoping that they won't recommend unnecessary work just for the hell of it.

We want to remove what looks like possibly concrete underpinning in the cellar if it isn't actually needed and replace a breeze block pillar with a crown post; and when the roof gets done, the current dormer window needs replacing with something the CO is happy with - current one is modern, horrible and built very lightly (surveyor amazed it hadn't collapsed) - and I need to see whether that part of the roof will need strengthening to take the extra weight of a heavier structure and a tiled gable front rather than the current flat roof. Fortunately the purlin wasn't cut, but a lot of rafters were removed. All done without LBC :roll: .

Not sure if a structural engineer is who we need for all of that - or just a really good conservation builder. Just don't want to end up with the whole house left as a pile of rubble - or making big and expensive mistakes!

 

[plasticpigeon]

Not knowing much about timber framed buildings, I can't add much, but wood below ground level doesn't sould a good idea or like how the house was originally built. Surely the ground level must have been raised over the years. I'm pretty sure that it is possible to support sections of the house if the sill plate needs replacing, but obviously it can't be done in one go.

 

[xanthe]

The house was originally built in around 1580, and I imagine it was initially on a brick plinth. It's currently 2 bays, but builder and surveyor reckon there was a 3rd bay that possibly collapsed at some point a long time ago (the house still leans). A cellar was added later (builder & surveyor say later, CO says original...) and the sill beams are now resting on that.

They are visible, very large, and possibly okay - lots of ventilation inside. Was just too much furniture in front to get to them easily during survey and stick a knife in or similar.

The road outside has gradually built up until the floor is now about 20cm below the ground level. Outside is bricks on earth, so water can evaporate, for a metre or so sloping away from the house and then tarmac. Would be hard to lower the level outside the house without the road sloping towards the house or creating a ditch! Neighbouring properties don't have the same potential issues as are much later and different build.

I have found postcards of the property from around 1890 and 1920 and both show the house with the current ground level, so it's at least 100 years that it's been underground so far. I know that alder likes its feet wet and are used as piles under Venice etc but not sure about oak!

 

[Flyfisher]

Is a sill plate the same as a sole plate?

Our house is of a similar vintage (1550) and is on a brick plinth that has been gradually covered up over the years, especially at the front of the house. Fortunately, I can lower the ground quite easily, but it needs to come down about 10 inches to leave the sole plate above ground.

We had some sections of sole plate replaced earlier this year. It's not such a big job really and need not be particularly destructive. Underneath the render, some of the panels have the original wattle & daub and some have brick infill - neither was disturbed by the sole plate replacement.

The biggest issue is to create sufficient space in which to work and I can't really see how it could be done without fully exposing at least one side of the sole plate. If the outside ground level cannot be lowered then it might be possible to do the work from within the cellar, depending on the layout, but if the new sole plate is going to remain buried in the ground then it will certainly have a shortened durability.

It does sounds as if some advice from a historic buildings specialist might be in order and I would recommend the CO as a starting point.

 

[tobydog]

xanthe - does your sole / sill plate have the vertical timber studs in it as would appear in a conventional timber frame? If it has then I'm struggling to see how you could replace it with anything other than another timber plate unless you build the studs into the new brick. What sits on the current plate?

 

[xanthe]

Of the original C16th part (the cellar runs under the whole of this part only and you can see sole plates on the ashlar on all four sides from inside the cellar):

Front and left gable wall - missing all the vertical studs. This is where the ground levels are higher than the floor-level.

Right gable wall is up against the much later house next door (sort of semi-detached) and all the studs are there and the sole plate is actually forming the 'skirting board' the whole length of the wall.

Back wall - now an inside wall and the studs are all there and the sole plate is now acting as a skirting board in the hallway.

There was a C18th extension with catslide roof that I presume was a service area and is now the hallway with a bathroom and kitchen. Kitchen was extended in 1970, but as part of LBC the timbers from the catslide roof with wallplate and the vertical studs were left in place right in the middle of the kitchen (ideal for bashing your head while cooking.

The timbers under the ground floor, especially the sole plates, are massive compared with elsewhere in the house. Surveyor says that they have been treated with some kind of preservative.

I guess I'm not going to be able to work out much more till we get the keys in January. I ended up going down to see the place 7 times before we agreed on the price, so I took an awful lot of photographs!

 

[xanthe]

The front and left-hand gable are all various chunks of brick from different times up to the wall-plates of the first floor. The other two walls are currently modern plasterboard or fibreboard between the studs (but not for long :twisted: )