Nailing Hessian into scratch coat to protect it?

[OllieCR0]

We have some builders currently half-way through lime rendering for us.

They've finished scratch coat ... but:

-> I think without wetting bricks first
-> have nailed hessian to this overnight (into the brick) until temperature consistently back to 5'c from Monday onwards

What impact is this nailing in of Hessian likely to have on the scratch coat and overall rendering? I assume a negative one.

And impact of not wetting bricks first either? (fyi bricks are fairly porous/spooled due to a) old cracked cement render allowing moisture in /freezing and b) us getting that cement render removed)

And what should we ask them to do? I'm thinking:

-> remove nails
-> fill in holes with fresh lime render
-> drape hessian from roof downwards, keeping 1-2 inches away from the lime render
-> drape plastic sheeting from higher on roof to keep area waterproof

Any advice very welcome.

(As background: we've had to stop these builders using PVA ("to help render stick"), Waterproofer ("to make mortar more workable") and Sika portland cement WinterMix ("to protect from frost"), so we're aware they're not experienced in lime.)

 

[stevethespreader]

You dont use water poroofer with lime its counter productive only hydrated lime is used with cement can you tell us what lime they are using?

 

[OllieCR0]

They're using for base and top coat:

1 part - CHAUX DE WASSELONNE – NHL 3.5
3 parts - Travis Perkins Plastering Sand

 

[stevethespreader]

Ok the 3.5 and plastering sand at a mix ratio of 3 to 1 is good but using cement, waterproofer, and pva ? No