Crazing in bonding

Status
Not open for further replies.

bryon

New Member
Have had to pull out a customers shower (rotten supporting frame due to leaking waste) and remove enclosure tiles (leaking shower valve).

Shower area needed replastering due to tiles pulling away existing plaster. Range of holes and depths up to about 15mm so I used bonding to level and then a thin skim of bonding to give a sound base for the tiles. Have done this loads of times without issue but whenever I've plastered in this customers house the plaster crazes.

Original background is sand/cement to blockwork with finish top coat (internal wall).
I removed all loose and degraded old plaster/tile adhesive and brushed surface to remove loose material.
I primed (religiously) with PVA (1:5) to all surfaces and let it dry for about 1.5 hours.
I then used bonding coat of PVA (1:3) and then levelling coat of bonding plaster to fill holes, followed by thin skim of bonding plaster to give consistent finish for new tiles.
There was no heating on and the wall was not in direct sunlight.

So why does the plaster craze? I suspect this is a suction issue causing shrinkage cracks before it sets. Can anyone with more experience suggest ways to overcome for future (and whether I can predict whether it will happen before I start plastering)?
 
thanks spunky. never used hardwall, is it a similar set to bonding. how come it stops the cracking?
 
Bonding is for low suction backgrounds ie painted brick, hardwall for high suction backgrounds ie block or brick.
 
probably cant mate ;D........i just think it helps the bonding adds the adhesion and the hardwall bulks it out to get in on thicker
 
Status
Not open for further replies.
Back
Top