I have been doing a little research about replacing the siding on a small circa 1920's bungalow. It seems the recommended process is to remove the existing siding then do the housewrap thing before installing the Hardiplank. I do recall when I replaced a small part of the siding a few years back, that the siding was attached directly to the studs. No exterior sheathing was present. Can I install the HP directly over the old siding or do I need to remove it and install sheathing first? Which would be a drag. Any advice always appreciated.