Slabs and wall have what they call 'Priority Based Connections'.
This means that the higher strength Building Materials will automatically override the weaker ones.
An automatic SEO if you like.
That is why the SEO will not work as the connection has already been made and the bits cut away can't make any further cuts in SEO because they are not there.
So you have 2 options.
Play around with the strengths of your building materials.
Or place the slab and the wall in different layers and set the intersection priority number (found in the layer settings dialogue) to be different for each layer.
Then the PBC will not occur and you can do your SEO as ther is nothing being cut away automatically.
If they have to be in the same layer then you can set the intersection priority number to zero.
Of course this will affect how other elements interact with elements in these layers.
Remember also to set the priority number in the layer combinations as well otherwise you will find they reset every time you change to a new combination.
You can of course have different settings in each combinations so maybe in some they do connect automatically and in other combinations they don't.
The best way is to sort out your building material strengths which may mean you have to duplicate some building materials but have them at different strengths for different uses.
Barry.
One of the forum moderators.
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