what to use and what order

[chirpychippy]

We had a conservatory built on the back of our house a while ago and one of the windows was bricked up enternally with a view to blocking the internal section at a later date. Today is the later date! I have taken the old sash out and have studded the gap out and covered with 12.5mm pb, allowing for 3mm back from the exisitng plaster finish. However, when I removed the Architraves some of the old plaster and render underneath came away "as expected" taking me back to bear brick.

I want to repair this damage myself rather than get a spreader in as its quite minor, but I am unsure of whether I should put a substance i.e PVA over the bricks first to provide a key and which coat I should apply first i.e Bonding Coat/Hardwall and do either of the mentioned stick to metal conduit as there is a run of just metal conduit. I can spread finish coat I just not sure what goes before it, thank you very much in advance.

 

[Richard C]

Use Bonding rather than Hardwall; PVA the day before & PVA again before you plaster out; let the PVA go tacky. It’s a good idea to break away the edge of the old plaster all around the opening anyway as this ragged edge provides a better key for the new plaster join. I should warn you that just blending in the new skim with the old wall is almost certain to crack around the join at sometime in the future. Bonding will stick to the metal conduit.

Best way to hide it is to remove around 4"-6" of plaster & render from all around opening back to the brick so that new board can be set onto the wall (& studding) as well as covering the opening, fill out the boarded area level with the surrounding wall with bonding, reinforce the edges with tape & then finish skim the whole wall. The old plaster obviously has to be thick enough to accommodate the thickness of the board but it will usually take 9.5mm in not 12mm. If I’m blocking openings for myself or family, I always prefer to block it up rather than stud it out, that way you avoid differential expansion between the stud & the brick wall & it will never crack.