Adding a storey on top of the house or digging out a basement: What's the better way to carve out an extra guest room or two?
Unless you are a basement dweller and you want to dig out your own niche in the dirt with little more than window wells to let the light in, I suggest adding an additional floor up top. Digging out a basement by underpinning can give you fantastic ceiling heights though it's still better suited to a home theatre than a bedroom. Having said that, the basement could be the ideal location for your teenager to hang out in with his loud but uncommunicative friends. The downfall of an additional floor up top is that your home's structure could require strengthening. Further, those guests you speak of may wear high heels that you will forever hear above your head. You'll also have guests wandering through your entire home on their way to and from their room, which will compromise your privacy. I would move the master suite to the top floor and tuck the guest room adjacent to the second-floor laundry room. This will annoy your visitors slightly, so they won't overstay their welcome, and if they are good guests, they might clean up after themselves. The best guests book a hotel.