feedback welcome...
NT
==Cause== Hairline ceiling cracks are normally caused by differential movement due to temperature & relative humidity, and nothing practical can be done to stop them. Attempts to prevent future cracking don't work. Sometimes people cau se damage trying to stop future movement.
==Fix== When hairline cracks occur, just wipe the crack with a finger with a bit of filler on. Wipe any filler off the surface and its done.
Occasionally the 2 sides of the crack move up & down relative to each other , and wiped in filler soon falls out. If this happens the 2 plasterboard ed ges need to be connected to each other so neither can flap. Lift a floorboa rd above, place wood strips above the ceiling and screw through the plaster board into them. Only use plasterboard screws, other types break up the pla sterboard.
Another fix for flexing edges is to drop large globs of plaster onto the ce iling from above to stick it together. This works well with lath & plaster ceilings, using a lime mix.
==Fix damage== Where damage has been done by gouging the ceiling & filling badly, the solu tion is to fill/level the damage. Do it well & its invisible. Some folk app ly excess filler & sand it down, its much easier IME to level the filler wh en its applied, not sand it later. If cracking is extensive it can be easie r to skim the whole ceiling.
Flexible fillers are ineffective since they have only slight flexibility, a nd the amount of flex required to continue to fill a hairline crack is 100s of %.
==Edge cracking== Small cracks are best filled the same way, just wipe on some filler.
Substantial cracking at the ceiling perimeter can be reduced by fitting cov ing or cornice, fixing it only to the wall. Cracking is still visible, but less.
==See also== [[fill]] [[filler]]