Joining plasterboard wall to blockwork wall

[gavos]

I live in a traditional 1880's mid terrace house. I have a tiny first floor bathroom in the rear two-storey addition. To increase the size of the bathroom I've taken down the rear internal block wall and built a plasterboard stud wall a couple of foot further into the rear bedroom. All has gone well so far and I'm now ready for plastering and then tiling. The remaining side wall of the bathroom (a non-load bearing internal wall) has been extended with stud work for a couple of foot before returning along the rear (so the new stud work is L-shaped on plan). I'm concerned that a vertical crack will appear part way along the side wall of the bathroom where the new stud work joins the original blockwork. The original wall is made of old clinker blocks with a very hard plaster/render over the top. I've put some frame fixings through the studwork into the blocks but how can I reinforce the plaster across this join to prevent cracks appearing and damaging the tiles? My scrim tape seems a little weedy for this job.

I hope the above makes sense, your advice would be much appreciated.

 

[roughcaster]

A straight join between a plasterboard stud wall and a solid wall would be difficult to tape..... Try this if you have enough depth,,,,, it would mean a slight alteration, and a bit of hard work, but if you cut a strip, of at least 3 or 4 inches of the old plaster/render away from the edge of the solid wall, from floor to ceiling, and then take off the sheet of plasterboard and refix another piece, 3" or 4" wider, but this time,overlap the sheet onto the solid wall, 3 to 4 inches, you could then fix the sheet back onto the stud as before, but you could also fix the sheet to the actual block wall itself too, with plugs and screws, giving you a much stronger joint. Just make sure it's screwed tightly to the wall, with no void underneath, you could even use a grab adhesive as well as the screws. Tape it over with a couple of pieces of tape vertically on the joint, and that should give it a better chance of the joint not cracking.

Roughcaster.