Q: I have stairs made with imported marble leading to my front door. The stairs have numerous stains - brown from leaves, bird droppings, etc - all I have tried, with little success, to remove these with muriatic acid. Can you recommend a cleaner?

A: Acid should never be used on marble; it etches the surface and could cause damage that will be impossible to remove without professional polishing by machine. As a rule, marble can be cleaned with regular detergent, as far as ordinary soil is concerned. However, marble is porous, and the kind of stains you have normally require treatment with a poultice made by mixing powdered whiting (chalk dust) with various chemical cleaners or bleaches - depending on the type of stain.

Your best bet would be to buy a marble-cleaning kit, which usually includes a combination of these agents and which comes with instructions for use. These kits are sold by many hardware stores, department stores, and marble dealers.

Q: How can I remove water-base interior wall paint from a brick fire-place?

A: About the only way you can do it yourself is to use a thick, semi-paste type paint remover. For bricks I advise the kind that can be washed off with water, this will simplify removal from the rough surface. Cover the floor and hearth with drop cloths, on top of which place several layers of newspaper, then slap the remover on in thick layers and let it soak for about 10 to 20 minutes. Scurb off with a stiff-bristle bursh dipped into detegent solution. This will get most of the paint off, though you may have to repeat the process on some areas. Bricks are very porous, so some of the paint may have soaked deep into the pores and will not come out easily, if at all.

Q: We have two rooms whose walls are covered with stucco and we want to redecorate by applying wallpaper to these walls. We have been told that there is nothing we can do to remove the stucco and we're stuck with it. Is this true, and is there anything you can suggest?

A: Textured interior walls (this is not really stucco, merely plaster or paint that has been textured) can be smoothed over by troweling on a layer of spackling compound to fill and level the voids and crevices. I must warn you, however, that this is quite a job and not easy for an amateur. Hiring a professional can be very expensive. Sanding sometimes works, but this is time-consuming and expensive, besides being messy. Sometimes the easiest solution is to recover the walls with gypsum board panels.

Q: One of our bedrooms adjoins our tenant's living room, the two being separated by a dry wall with about a two-inch space in its middle. Sounds transmit so easily through this wall that we can hear their television - even their talking. Can you give us some suggestions about how to stop the sounds from one room to the other?

A: One way is to construct a second wall a couple of inches away from the first one, with no part of one wall touching the other. Then put insulation in the space between the two walls.

Another way is to rip the dry wall panels off on only one side of your partition, then put up another set of studs on this side, but stagger them so the new studs fall between the old one, and so that the back of each is about three to four inches away from the old dry wall panels on the other side - and not touching any part of the old wall's framework. Then weave insulation between the two sets of studs and put new wallboard up on this side. This will create a new wall twice as thick as the old one, with separate framing for the panels on each side. CAPTION: Illustration, no caption, By Bethann Thornburgh - The Washington Post