Work required to get rid of black walls?

You need plastering and mold remover

Solve damp/ plumbing issues.Remove all damaged plaster and dry line then plaster

You will need a mould removal specialist.

1. Identify the Cause: First, ensure that the flooding has been properly fixed. If the leak isn’t addressed, you’ll continue to have moisture issues.

2. Mould Remover: Use a mould remover (e.g., a diluted bleach solution or a specialist mould cleaner) to treat the affected areas. Scrub the blackened walls thoroughly to kill the mould spores and clean the surface. Be sure to wear protective gear.

3. Dry the Walls: After cleaning, ensure the walls are thoroughly dry to prevent further mould growth.

4. Plastering: If the plaster is damaged or crumbling due to the water exposure, you may need a plasterer to re-plaster the affected areas once the walls are fully dry. In some cases, you might need to apply a mould-resistant plaster or sealant before re-plastering.

By tackling both the mould removal and the potential plaster damage, you can restore the walls safely.

Yes you take of damaged plaster and let it dry out if still damp treat the damp and go from there

If the walls in your utility room are black due to flooding, it's likely that you have mold or water damage. Here’s what you should do:

1. Assess the Damage: Check how extensive the damage is. If the walls are soft or crumbling, you may need to remove sections of the drywall.

2. Mold Removal: If you see mold, it's important to address it before doing any repairs. You can use a mold remover solution or a mixture of water and vinegar. Make sure to wear protective gear like gloves and a mask.

3. Dry the Area: Ensure that the area is completely dry. You may need to use fans or dehumidifiers to help with this.

4. Repair the Walls: If the damage is significant, you might need to call a plasterer to fix the walls properly. If it’s just minor, you can patch it up with new drywall or plaster.

5. Repaint: After everything is dry and repaired, you can repaint the walls with a mold-resistant paint to prevent future issues.

It's crucial to deal with the mold issue first before considering plastering or painting. If you're unsure about the extent of the damage, it might be a good idea to consult a professional.

First you need to try to solve the issue with your neighbour and the get you insurance to look at the property because removing mould with a cleaner is virtually impossible so realistically it needs removing to solve theissue

Both

Mould can be removed with a mould removing solution. But if the mould has been caused by flooding , It is more then likely that there will be some plastering to be done here or there. You will need to check for areas where the wall is hollow for blown plaster

Depending on how bad the mould is, you may have to take it back to the original brickwork and then bond it and re- plaster or put a stain block on and repaint