I need to check if the cracks in several walls at home are moving.
I know I can hammer in three nails around the cracks and measure the movement over time with a digital caliper. This is better than the old method of using small gypsum plasters on the cracks.
I remember having seen small transparent devices afixed across the cracks to do that.
Can anybody point me to where I can find such devices or similar ones?
Thanks,
Antonio
They are microscope glass slides:
AWEM
Most surveyors still seem to go for three test points (you can get posher versions with proper defined centres to measure to - but nails or screws would probably do.
The accurate way would be using something like these:
Microscope slides (glass) aradlited across would show movement or not (ie they crack). Not so good for measuring the actual movement though. But it is the classic way if you want to prove a crack isn't moving...
Antonio,
Take two pieces of glass of equal length, scratch a mark in both pieces at a distance from one end, stick one above the other on the wall on both sides of the crack on one end of each only (to allow movement of the glass as the crack widens or closes) with the two marks aligned.
As the wall (and crack) moves, the scratch marks will open or close, showing the distance of movement (if any) and its direction.
Whatever you use, do not stick both ends of the tell-tale over the crack and expect it to break if the walls move (the won't, unless you have major structural movement [and you'll see that without tell-tales]) - always leave one end free.
Or google for -- glass tell-tales -- for more info.
As a matter of interest, if you have access to a glass cutter and some scrap (or broken pieces) of ordinary window glass, you can make your own and use something like an epoxy resin or contact adhesive to stick them to the wall.
Or using the same method, you could even cut the pieces out of the old ubiquitous empty bake bean tin - and stick these on the wall (or you even use a couple of small masonry nails to fix them in this case).
Cash
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