I use a Fein Multimaster with a flush cut E blade. Dremel also has a much cheaper version called a Multi-Max. Lay down a metal speed square where you want to make a cut. Tape it down good using blue tape and then make your cut using the fat part of the speed square as your guide. Cut back slightly at an angle so the new board will drop in clean.

This is an old thread ... in fact, I've sold the house and moved. But to provide an update: 1. We put in a perimeter board to make a finished edge. But I was able to find examples of both approaches (finished edges, and cut-off ends) in my neighborhood during long walks to spot examples. 2. Partly based on the comments in this thread, I went back to the contractor and told them I wanted to remove all layers of wood they wanted to just cover up. We went down the joists, pulling off the layers previous home owners had stacked over time. We sistered a couple of supports that it seemed would benefit from that attention. Then we installed new composite porch boards per the way they were designed to be used. I don't know why local contractors in my former neighborhood try to short-cut everything ...I think there is a lot of local practices that are just a bit oddball that they tend to default into following. And they just assume everyone wants the cheapest solution no matter what. For example, for a long time in this particular area many people just slapped plywood sheets down on covered rowhose porches, then painted the sheets. So when I tried to upgrade to composite, which requires a different approach, the local response kept coming back, "we'll take the top layer off and build on what's underneath." I asked about three times if that was what we should really do, and only ever got that answer. I ended up having to say point blank I didn't want that and was happy to pay more to do what is standard. But it got done! Thanks to all.

Cement board does NOT add stiffness. You need to read the instructions for the tile to find out the deflection rating for the tile. Then you need to MEET or EXCEED that rating on your subfloor. Plywood is your most reliable way to do it. The house's age suggests it was built before the 1970's. Am I correct? I had a house that just turned 105 years old last year. It had the slanted wood subfloors (those are NOT hardwood floors...they are subfloors). This type of construction was common at the turn of the 20th century - into the 1940's - 50's. The reason I ask? Asbestos and lead. *If your house is as OLD as I think it is, you could have a house FILLED with both. Asbestos was 'banned' in 1982...but the companies were allowed to sell off their MILLIONS AND MILLIONS of square feet of stock for many years afterwards (1989 or so). And lead based paints = regulated in 1978...but again the old stock was allowed to be sold off for a few more years. Lead pipes? Right. As a DIYer you will be responsible for knowing ALL of the building requirements you would expect from a professional...and that includes what to do TO FIND OUT if you have asbestos/lead AS WELL AS how to DEAL with it once you find it. Your local State laws will help guide you. Have you tested for asbestos or lead in any of your surfaces? That's where I WOULD start. The rest comes with the answers you find.

You are not going to be able to remove entire, nailed tongue and groove boards without at least a bit of damage, and trying to do so to move around the attic opening is too big a task for what you want to accomplish. If it were me, I'd remove the trim around the attic opening and then carefully cut out the tongue and groove boards that were to the left and right of the opening. You wouldn't have to take out entire boards, but you could cut out partial lengths so you had staggered joints, and have new tongue and groove milled to the old dimensions that you would use to patch in. If you have a skilled carpenter do this, the staggered butt joints will not draw attention to the fix. Then you can cut in a new opening where you want, trim it, and paint everything. Whatever you do, don't put sheetrock over that great ceiling.