- Changing from your existing masonry fireplace to the linear gas fireplace in the photo you posted a link to would likely be fairly expensive, as it would require removing/modifying the masonry of your existing fireplace, but there are other approaches you might consider. One of the keys to modern is minimalism. You might try keeping the appearance as uncluttered as possible - perhaps by removing an existing mantel or stripping away other elements to leave only the most essential parts. If it is a wood burning fireplace, the building code requires that you leave non-combustible hearth protection in front of the fireplace, but you might be able to change the hearth material to make it more modern (pink wall with hearth flush on floor). The other thing you might consider is changing over to a modern gas burner, with glass media or stones (first photo, with black mantel). There are gas inserts that are beautiful as well last photo with stone wall), but the investment goes up when you get into a full system with firebox, surround, venting etc. If you have a photo of your current situation, we might be able to tailor our suggestions to be more helpful.

A thick concrete wall can keep your house cool. Steel will make your house hot unless you insulated the walls well. Insulated walls don't work very well in a flood zone. When they get wet, you need to tear them apart. You will need concrete for the foundation most likely unless you are driving steel pylons. There is probably a combination of the two that will suit your needs best. It would be helpful to know what you want to achieve by using steel. There are advantages to both. Steel floors can be cantilevered further. It is easier to make bigger window openings. Floor and roof spans can be lighter and quicker to build with steel, but the roof will get hotter and therefore need good insulation and need to be well ventilated. These are just general assumptions of certain building practices so that you know what to ask people where you live. The practices and resources vary from place to place and building something for a specific purpose can change the benefits of one material or the other. My best guess is that you will probably want to use both.

I think this was just brick added to a wall so you should not need anything other than mortar but IMO this looks odd just put in the middle of a wall I would remove it

Thanks for both of your responses CUBSpaces team and Shweta from Shades studio. It really gives a clarity about possible consequences. I am now doubt free about changing whole things in Bathroom as it will be interconnected. However will appreciate your opinion on few things: 1. Kitchen wall tiles: I have those from countertop height to roof(almost area of 6X15 feet) which are good and not hollow. I changed countertop 5 years back without any damage to these tiles. It might cost me another 10-15 K, but I feel the whole process and quantity of wasting old good tiles makes me little sad. 2. kitchen countertop: Made new around 5 years back. I don't expect to get it all intact. But large pieces can be cut and can be used as top for other freestanding structures like dishwasher, front load washer, heighten base cabinets, etc. 3. Plywood: I don't mind giving enough labour charges for old sheets recycle. I am planning to use doors, loose sheets(like kept on bed frame of settee frame.) or parts of big frames like settee. I am keen on reducing waste than to save money. You can see various DIY ideas by western people, who remove or sand laminates and re-paint furniture, or carefully remove hollow tiles and re-attach them. Some are also re-painting ceramic tiles. I am just asking myself: Are we creating more and more waste by use and throw approach every 10-15 years, just because we can afford it?