How to replace damaged floor boards, get rid of wood borers

Q Our son removed wall-to-wall carpeting and found several places where the hardwood flooring was eaten by either termites or dry rot. The largest spot is not more than 8 or 10 inches long, and all damage involves but one flooring board. How can these damaged portions of the floor be removed and replaced? Gloria Charter Los Gatos, Calif.

Replacement of hardwood boards in an existing floor is tricky, but possible. Here are some steps to take, according to R. L. Thompson of the Virginia Hardwood Company, Phoenix, Ariz.:

* Rip two parallel saw cuts the length of each flawed board. Take care not to damage the adjacent boards.

* Chisel out the center between the cuts and then chisel out the remaining sides. Work from the outer side to the center so as to prevent damage to the side boards.

* Clean the subfloor.

* Select a new board that is longer than the one being replaced.

* Cut the new board to the desired length at the end with the tongue. Save the grooved end.

* Cut off the bottom half of the groove on the sides and end.

* Slide the board into position, using panel adhesive on the bottom and/or face-nail. Countersink the nails and fill to prevent damage to the sander.

* Sand, stain, and finish as necessary. Staining the new pieces to match the existing boards is difficult because the age-coloration effect cannot be matched. Q We recently bought a log house which had been ''tented'' for wood borers in 1982. The borers returned, and the cabin was again ''tented'' last summer with Vikane. Three weeks later we noticed unmistakable piles of sawdust. Is it possible that the wood borers are resistant to Vikane, or was the pest-control work done improperly? Is there any other chemical we should try? Lee Godfrey Burnsville, Va.

To our rescue again comes a reply from George W. Rambo of the National Pest Control Association, Dunn Loring, Va.''First,'' he asks, ''what is the wood borer in question? It could make a difference in treatment. The piles of sawdust could be from old activity, not new.''

Insect identification would aid here because different beetles emerge at different times of the year.

''The Vikane, although not a good ovicide (kills eggs), should stop activity if the fumigation was done correctly. There is no resistance to Vikane. Another method is to apply a liquid chemical to the wood; either Lindane, or Dursban TC or LO, are registered for this. I would suggest Durban LO for indoor use, but any of the three for outdoor use (LO has no odor).

''If there is a question about activity, entomologists at Virginia Polytechnic Institute (VPI) in Blacksburg, Va., have been studying wood borers for several years. Contact Dr. Bill Robinson at VPI.''

No question that we have fired to the people at the association has yet bugged them.

If you have a question on designing, improving, or maintaining your home, send it to the real estate editor, The Christian Science Monitor, One Norway Street, Boston, Mass. 02115. Forrest M. Holly is a longtime California builder now living in southern Arizona.m