Timber framed bay render - help required

[Dan92]

Hi all, new here so please go easy on me, used information on here a lot which has proved very helpful but I have just signed up.

currently renovating our 1930’s semi

The render below between my living room and bedroom bay windows is cracking and appears to be falling away from the house on one side, leaving a gap at the top where rain can get in.

In a couple of weeks time my windows are getting replaced and the fitters suggested I have this removed and ‘prepped’ ready for later on when we do intend on rendering the house, probably with a a silicone render - K rend?

I am not a plasterer by trade but I tend to pick up most things and would like to do this bit of work myself over the weekend, but would like to get a few pointers as I keep finding different Information.

Do I need to fit Ply to the frame first?
I have seen some suggestions to ply the frame, membrane, batton, cement board etc.
but I have also seen advice to fit cement board directly onto the frame, is this right? frame, cement board, then render directly on?

is there any other detail I need to consider? Jointing tape, beads etc?

not sure if it makes a difference but both rooms are currently back to brick, and the intention will be to insulate the bay area prior to plaster boarding inside.
another worry Ive got is damp inside once altogether if I’ve not thought it through properly.

picture of outside of house below

thanks in advance for any help offered

 

[JohnD]

I've had one of these, and I'd suggest including a breathing roofers membrane, and plenty of insulation, in the bay. The internal plaster probably needs renewing as well, so you can get at the void easily when you strip it off.

 

[Dan92]

Thanks John, do you think I should be fitting ply to the frame before membrane? Then batons then cement boards?
I plan to insulate from the inside, I think this is the right thing to do
Inside is currently stripped back so that isn’t a problem

 

[JohnD]

One of the rendering guys will know better. I expect you have a rough studwork frame, if it was me I think I would ply it, put the membrane on, counterbatten so there is a gap for any damp to escape, then a cement board to be rendered, with the insulation in the cavity inside the ply, as much insulation as will fit, and stuffed well into the space between the floor and the ceiling to prevent draughts, then your indoor plasterboard. These lightweight bays don't have enough weight to block out sound so I'd prefer two layers. I think the membrane should overlap the downstairs bay to prevent water getting into the gap.

But this is not my line of work so may be nonsense.

In Switzerland I saw rigid foam boards being used, with cement boards bolted through them, and the K-rend or similar over the top. I didn't notice the joints being taped but I expect they were.

There may be a professional way of detailing to keep the rain out.

 

[Dan92]

Thanks John really appreciate that