A method of retro-fitting a moisture detection fitting in the wall of a building in accordance with the following steps: forming a space which proceeds into the wall; and inserting the moisture detection fitting into the space such that a probe of the fitting: 1) presses into timber framing within the wall, or 2) stops short of timber framing within the wall but contacts a moisture absorbent filler forming part of the fitting and wherein the filler can absorb moisture from the timber framing. The moisture detection fitting being fitted substantially permanently such that when it is in use a moisture detection device can be detachably connected to the fitting outside the wall and use the probes, and if appropriate the filler, to measure a moisture content of the timber framing.