Is my bag of bonding useless??

[Stu1H]

Hi all, need some help. I'm attempting my first plastering job where i've bricked up an internal doorway and chased out for some electrics.

I bought a bag of bonding just over a week ago and its been stored in the shed (which is insulated!!) off of the floor. I came to mix some up by hand today and it was quite grainy, so out came the paddle and drill and i get the same result (i'm adding plaster to water and not the other way 'round).

I'm assuming the bonding should be a very fine powder but it isn't. Is this now useless? Also, I used some on where I've chased out, do I need to re-do this??

Also one further question .... is it really essential to build up the bonding in layers of 8-10mm or can i slap it on in one go about an inch thick???

Thanks.

 

[roughcaster]

It's meant to be like that. Multi finish is a fine plaster, but bonding coat is a coarser plaster. For your other point, it's always best to bring out a thick coat, in 2 or even 3 coats. If you put it on in one thick coat, it will slump, and do no good at all. The chases that you've already done will be ok,, as long as you have prepped them properly.

Roughcaster.

 

[Stu1H]

Excellent ... many thanks.

Can crack on nice and early in the morning now.

Cheers.

 

[roughcaster]

Forgot to mention,,, to provide a key,, scratch each coat like in the pic, plus let each coat tighten up or set before you put on the next one,,,, depending on your ability.

Untitled

• roughcaster
• 14 Jul 2009
• 5

Roughcaster.

 

[Richard C]

I always us Bonding over electrical chasses & as a base on rough walls but I wouldn’t have picked for a “brick up”; what bricks/blocks did you use? Bonding has excellent binding properties but is a relatively soft base plaster & intended for use on low suction backgrounds; if you used high absorption blocks to brick up, make sure you seal it well & apply plenty of water prior to plastering or it will craze like hell. Otherwise follow RC’s advice & it should be fine.