An introduction... Renovation + 1950s + subsidence = a challenge!

[alfaTom]

Very quick lunchtime investigation on the downstairs crack reveals a fair amount of roughfill, and what looks to be a metal mesh, I assume from the previous subsidence repair as there were references to repair meshes being installed.

First image is a small cutaway as well as investigating the coving - this is plaster so explains the tears.

 

In the below image you can see where I've come across the repair mesh as we as something else under it, not sure what it is yet but it looks to just be sitting in roughfill again.

 

 

Below the roughfill is what I assume to be plasterboard as it's not solid like a lintel, but it's also sat about 10-15mm beneath the top layer of plaster which seems excessive. The doorway cut into the wall is about 42cm in depth which is much thicker than other external walls in the house are roughly 28cm there is definitely some buildup on it...

I will have a closer look at the assumed plasterboard as well as the crack to the left of it after work.

R.e. the next steps:
Drain repair sounds sensible, I am just waiting on plans coming back so I can work out best place to put new soakaways in. Thankfully the size of the gardens mean I have a decent choice of locations as long as they pass percolation tests.
 

3 hours ago, George said:

You may still get fine cracking for the lifetime of the building but if I could do all the above for £10k, bank the £20k and just reapply caulk and paint every 5 years I'd be happy. 

 

I would be more than happy with this tradeoff too. Assume at this point we'd level internal floors/ceilings/walls as necessary and leave the house to it's controlled movement.

Edit: For clarity, this doorway is one we would be planning to block up as part of our plans.

Edited July 14, 2023 by alfaTom

[Mike]

 

3 hours ago, alfaTom said:

Below is their suggested works, which involve resin injection across the majority of the front elevation as well as around the gable ends.

Partial underpinning / soil stabilisation raises new issues. You need the entire building to act as one structural element for it to remain stable and crack-free. There's a risk that the part of the building that has been underpinned swaps from being the least-well supported part of the building to the best-supported part, which could still cause differential movement. That's not to say that it should never be done, but it does mean that whoever is designing the solution needs to have carried out a full investigation first. Personally I'd be wanting an independent structural engineer to be doing that, not a contractor.

[alfaTom]

Got bored of work - the crack is above my desk so went back to it.
Found what I believe to be a timber lintel behind the plasterboard.

 

I am not sure what "repairs" this company did previously but it currently looks like they chucked repair mesh over the old plasterboard and covered it?
More needs to come off to find out how far the lintel goes as well as the makeup in between, but if the wood has dried or shrunk I can see this causing some movement upstairs...

 

1 hour ago, Mike said:

 Personally I'd be wanting an independent structural engineer to be doing that, not a contractor.

 

Agreed, I think next steps will be to provide our SE with TP & SI reports, plus the suggestions from the underpinning company.

[Mr Punter]

6 hours ago, alfaTom said:

I honestly did not know about the "upside down" ground aspect and this is something I definitely need to look into more, especially as we'd rather use that cash on other parts of the property if the underpinning is going to cause issues with the rest of the property.

 

We are on land that has about 2m depth of fairly solid clay and made ground, then 18m alluvial silt, then hard chalk bedrock.  The previous buildings on the site had fairly shallow strip footings with no sign of movement.  Our replacements are 4 storey and are on 25m piles.  Anything founded between 2m and 18m would not be very stable.

[alfaTom]

I have been a bit quiet recently - unfortunately, the weather at the weekend was terrible so no investigations outside were completed. I did however get the old cylinder lawnmower running again in the (relative) safety of the garage!

 

I did finish the cut-out above the doorway though. After getting through a layer of plaster, roughfill AND plasterboard I found the lintel over the doorway.

It looks like there is a metal lintel (can be seen below the timber and in the shadow) with the timber resting above it.

I need to get more of it cut out to see how it sits but I didn't want to disturb it too much.

Waiting on the SEs to respond to my queries at the moment around the soil vs drains, and I am waiting for the underpinning company to come back to me with answers about complications from partial underpinning and more info on guarantees.
When I get more information I'll update this thread so the information is there for anyone in the future that may need it.

[Mr Punter]

That is quite a bewildering selection of materials!  Have you checked that the wall textured coating does not contain asbestos?  Given the age of the property you need to be a bit cautious.

[alfaTom]

45 minutes ago, Mr Punter said:

That is quite a bewildering selection of materials!  Have you checked that the wall textured coating does not contain asbestos?  Given the age of the property you need to be a bit cautious.

 

It's certainly a variety pack! Curious to see what I find elsewhere. I may try to cut the plasterboard below off so I can get almost a cross-section idea of the lintel. A shame the SE's seem to be taking their time coming back to me at the moment as that is holding us up currently.

My understanding is that the wallpaper is newer, from 2012 when some work was done to the property. It doesn't seem to have a vinyl layer so it which reduces the chances as far as I am aware.

There is plenty of asbestos elsewhere though; garage roof sheets, soil pipes, guttering etc as well as some tiles in the downstairs w/c.

[Iceverge]

Demo and rebuild! 

 

Its the only way😬.

[alfaTom]

I return... nearly 18 months later.

The project is still ongoing, but I thought it was worth updating everyone on our experiences so far. I admit we've probably made a few mistakes but as a first attempt at a big project I'm pretty happy how we've dealt with issues and moved on; every day is a school day! If any of this helps anyone else then it's worth it even if I look a bit daft during it!

So - onto the project.

We started by demolishing the old extensions since the foundations for them wouldn't be up to supporting a floor above them, plus they were built inadequately for our needs (solid walls, weird floor buildups, even weirder roofs).
 

There was plenty of advice on this site around the existing foundations and how to proceed with them which we really appreciated, but in the end we were led by the structural engineers and underpinned the property for peace of mind to avoid any differential movement.
The extension foundations are piled down to about 8-9m and the existing property was cantilever underpinned using piles too. Overall we're pretty confident the house won't be going anywhere (we now have 36 piles!)

 

We've then wrapped a fair chunk of the house in a new extension to better use the space, and put the poorer performing old external walls further into the property. Cavity is 200mm with 190mm PIR made up in two layers incl interlocking boards and tape, and the flooring is 240mm EPS insulation in the new areas, whilst we've just finished digging the old flooring out of the house which should be insulated to 170mm. I'd like more here but we're restricted by the depth of existing foundations which is a shame.

 

The old electricity supply has gone from overhead to a nice new underground supply, complete with 3ph up to the DNO supply head so we're future-proofed (still only 1ph currently) and I'm waiting for a response to my request for a new water supply.

 

Wet UFH is throughout, with the oil boiler gone and an ASHP to replace it (When I can get an installer on the BUS grant that won't rinse me). Spent a fair bit of time playing with Heatpunk and Jeremy's spreadsheet for heat loss predictions which is fun when half the property is 200mm cavity and the other is 50mm. I really wish here that we'd stepped the walls outwards and then EWI'd the older walls but I didn't think about this until it was too late - a good reminder to plan ahead here.

I'm also scheming for 10kWp of PV to go on since we're having a new roof fitted. The savings in tiles & labour lets me man-maths my way into some GSE trays and panels 😁

 

My current focus is looking at the air tightness, not as much of an issue in the new section but the older part of the house is good fun, so I guess there will be updates on this part from time to time as I'd love to get MVHR fitted as well.

 

Words can be boring sometimes, so the tl;dr is:
should we have listened to you all knocked it all down and started from scratch? In hindsight, Yes 😂
Did we? No... (Be gentle 😳) time to learn from it and make the best of it!

 

And the pictures:

 

Steel reinforcement for ringbeams in place after piling at the back

 

Starting the build to DPC

 

Second lift and on the way to wall plate.

 

Will maybe dump a few more before & after shots in the coming days or a specific focus on parts if anyone is interested. Poor house has been battered about a bit - for the greater good I hope! 

 

[MikeSharp01]

Quite the journey you are on there, great to get an update. What's the fun of air tighting an old build like. Our new build is very good, house went up 1 degree as I worked in it today but here, in millstone Manor, it went down 4 degrees while I was out - so I need to get it more air tight. Done some windows and door resealing need to start on the upper works now! Its brick built 50mm cavity with insulation in places. Any tips?

[Mike]

40 minutes ago, alfaTom said:

Will maybe dump a few more before & after shots in the coming days or a specific focus on parts if anyone is interested.

Please do :)

 

It's good to have an update and to see what you've been up to!

[Roger440]

Interesting stuff!

 

[Gus Potter]

2 hours ago, alfaTom said:

The project is still ongoing, but I thought it was worth updating everyone on our experiences so far.

Much appreciated. Your post is a mine of infomation.

 

So that is a big thanks from me!

[jack]

@alfaTom, would you mind if I moved this post to the relevant sub-forum (probably https://forum.buildhub.org.uk/forum/73-foundations/)? As @Gus Potter says, there's a lot of useful information in it, and it's likely to get lost in the Introduce Yourself sub-forum.

 

Thanks.