Concrete Block Extension Connection to Old Slate Wall

[JACKROGERS7]

i am wondering if anyone can help. i am an architecture student who is curious on a connection between an existing old slate building and a new extension .

any help/ advice would be massively appreciated

My Project Includes a 2 story old slate building located in the lake district from the 1800s (Slate external apperance ).
The current wall build up includes a 575mm thick slate wall with 25mm of internal lime plaster.

i want to add a 1 story lean to roof concrete block extension (as the main load bearing walls) along the eaves and gable wall.
The extension wall build up from inside to outside is :

100mm concrete block wall
100mm insulation
50mm SureCav Cavity
110mm slatestone wall

Question : does anyone have any advice on how i can 'fix' a concrete block wall against a slate wall.
I know its not the best but i asked AI as i was clueless which suggested a 10-20mm seperation gap which would include wall ties and mineral wool insulation.


i have attached a corner floor plan for the Image to explain the colours

1. Light green is a corner wall of the 575mm existing slate wall with 25mm internal lime plaster

2. Dark green - is the 110mm slate wall which is used to match its surroudings
3.black layer - is a 50mm cavity using surecav 50
4. pink layer - is a 100mm insulation layer
5. blue layer - are the 100mm concrete dense blocks

 

[jj4091]

Knock or cut holes/ slots into the exsisting wall as you build up the extension cavity wal and build your concrete blocks and new slate into the outer skin of the slate of the old wall then reinstate the holes/slots to tie the new wall into the old one.. Do that several times as your extension rises depending on how high your new wall is. Your waller/builder should advise what's the best way to do it but that is how I was advised and did ours. It's been ok for 30 years.

 

[noseall]

i am wondering if anyone can help. i am an architecture student who is curious on a connection between an existing old slate building and a new extension .

any help/ advice would be massively appreciated

My Project Includes a 2 story old slate building located in the lake district from the 1800s (Slate external apperance ).
The current wall build up includes a 575mm thick slate wall with 25mm of internal lime plaster.

i want to add a 1 story lean to roof concrete block extension (as the main load bearing walls) along the eaves and gable wall.
The extension wall build up from inside to outside is :

100mm concrete block wall
100mm insulation
50mm SureCav Cavity
110mm slatestone wall

Question : does anyone have any advice on how i can 'fix' a concrete block wall against a slate wall.
I know its not the best but i asked AI as i was clueless which suggested a 10-20mm seperation gap which would include wall ties and mineral wool insulation.


i have attached a corner floor plan for the Image to explain the colours

1. Light green is a corner wall of the 575mm existing slate wall with 25mm internal lime plaster

2. Dark green - is the 110mm slate wall which is used to match its surroudings
3.black layer - is a 50mm cavity using surecav 50
4. pink layer - is a 100mm insulation layer
5. blue layer - are the 100mm concrete dense blocks
View attachment 403439

Screw-in (fish-tail type) ties?

 

[stevie888]

Keying the walls together will give rigidity which may come back to bite you if there is any differential movement between new and old foundations. This is a real possibility given the modern insistence on ensuring the new bit doesn't move without considering what the original structure is doing. Firfix channels are the normal approach (and a lot less effort than keying in)

Not clear ir this is real or a student project but consultation with Building Control ahead of the work is always a good plan with anythng that's a bit out of the ordinary.

 

[^woody^]

You should think in principles, not detail.

When joining new to existing, or modern construction to traditional, there will be movement - be it initial settlement, seasonal structural or ground movement, or on-going thermal/differential movement of the structure or components.

You should expect this and design not only to accommodate this (flexible restraint) but also maintain a weathertight joint following any movement of the structure.

You need to determine what movement will take place - for this project scenario you should show that you have considered the various possibilities, pick those which will apply to your particular project and then design for those.

You basically make these scenarios up so that your design details works - pick a type of ground (eg stable/unstable soil), pick an exposure (eg coastal/inland), pick budgets and aesthetics etc. Then specify your design to reflect the situation you have detailed. Do this and you can't be wrong.

For the actual ties, you can specify either proprietary systems such as those from Simpson Strong-Tie, or detail a bespoke method of ties built in to mortar joints or fixed to the wall face.

Then consider the weather sealing. A epdm strip or mastic product would be normal, but if the existing wall face is uneven, how will an uneven joint look? What's the life of the joint sealant you propose compared to other components?

With these hypothetical projects, there is rarely a right or wrong, but you must be able to justify your decisions and reasoning, and that is what the assessor will be looking for.