Do I REALLY need to prime concrete blocks before dot and dabbing?

[Thorfun]

it seems opinions on the web differ. some say PVA, some say a Plastering Grit, some say just soak the concrete blocks with water and some say don't bother with anything! what's a person to do?

 

they are new blocks (although the walls were built 4yrs ago) so it's not like they've got old plaster or render on them or paint or anything.

 

it's not a large area either with a small area around a door, a short wall (800mm wide) and in a cupboard under the stairs. do I REALLY need to prime?

[crispy_wafer]

Wipe em down, get rid of any dust/loose material, a bit of moisture on the wall will slow down any moisture transfer from the adhesive, which may or may not help… depends on how loose the mix is, with mine some walls i damped down, some I didn’t, looks like it has made no difference to the end result.  In your case I’d probably not bother. 

[Oz07]

Mix a blob of adhesive up, dab a bit of board on and try to get it off in a week. No prep required usually. If excessively dusty give it a brush. I certainly wouldn't be wetting it immediately prior. Might be hard to dab the boards to a straight edge

[Thorfun]

1 minute ago, Oz07 said:

Mix a blob of adhesive up, dab a bit of board on and try to get it off in a week.

No time for that! Want to get it finished this weekend so I can tidy up next weekend for the plasterers the week after. 😉

[Nickfromwales]

Avoid that Sineat(?) adhesive. Was getting sucked dry in no time, and boards weren’t staying stuck to it if any open time had been introduced. 
 

Switched back to Gypsum and totally different results. Client bought Sineat stuff as it was the path of least resistance, but even their plasterboards were shit in comparison.

 

If a roller dipped in 50/50 SBR/water solution, put on with a shaggy roller is cheap and simple, then I’d say sizing the walls the day before to bind the surfaces would be a no brainer. Not exactly something you can revisit, is it?

 

Don’t get lazy now, get your finger back out and put in the time and effort 🫡. SBR is cheap enough, and can even be applied with a Hozelock spray bottle that you pump up, but you Siri need to take a soft brush to the wall (hence the roller application as it kills both birds). 

[Thorfun]

1 hour ago, Nickfromwales said:

Avoid that Sineat(?) adhesive. Was getting sucked dry in no time, and boards weren’t staying stuck to it if any open time had been introduced. 
 

Switched back to Gypsum and totally different results. Client bought Sineat stuff as it was the path of least resistance, but even their plasterboards were shit in comparison.

 

If a roller dipped in 50/50 SBR/water solution, put on with a shaggy roller is cheap and simple, then I’d say sizing the walls the day before to bind the surfaces would be a no brainer. Not exactly something you can revisit, is it?

 

Don’t get lazy now, get your finger back out and put in the time and effort 🫡. SBR is cheap enough, and can even be applied with a Hozelock spray bottle that you pump up, but you Siri need to take a soft brush to the wall (hence the roller application as it kills both birds). 

Interesting how that I’ve had 3 responses and there’s still no real agreement! 😂

[crispy_wafer]

Haha, used siniat boards and adhesive 🤣, no problems, had a bag that was slightly out of date, that stuff went off quicker than Usain Bolt and the board didn’t hold, but that was me being a tight git, rather than the materials!

Edited 22 hours ago by crispy_wafer

[crispy_wafer]

44 minutes ago, Thorfun said:

Interesting how that I’ve had 3 responses and there’s still no real agreement! 😂

If you’ve any doubt, you’ve got nothing to lose by sizing the wall with a splash of sbr and water, it certainly won’t harm the job.   IMO The mix of adhesive is the biggest factor.

[Thorfun]

1 hour ago, crispy_wafer said:

If you’ve any doubt, you’ve got nothing to lose by sizing the wall with a splash of sbr and water, it certainly won’t harm the job.   IMO The mix of adhesive is the biggest factor.

Sure. And I’ve thought about just mixing up some PVA but I wanted to get it finished tomorrow and if I have to paint it on and let it dry then that won’t happen! 
 

I’ll sleep on it and see how I feel in the morning. 

[Thorfun]

So, it turns out the question I should’ve asked is “Should I REALLY be allowed anywhere near a plastering trowel?”

 

to which the answer is a most definite NO!!!

 

I should’ve learnt from when I first tried plastering that I am rubbish with a trowel. I just made a mess. 
 

ended up giving up, scraping it all off and went back to metal frame instead. 
 

if I ever ask a question about DIY anything that involves a plastering trowel please tell me to not be so f*****g stupid and to pay a professional. 

[Oz07]

I find a bucket trowel easier to throw dobs on. 

[-rick-]

You never know if you don't try!

[Thorfun]

19 minutes ago, Oz07 said:

I find a bucket trowel easier to throw dobs on. 

Thanks but I’m never trying that again. 

[Oz07]

I'm also terrible at wet trades. I think a lot of the skill is getting consistentcy of the mix right whether it be mortar, adhesive etc etc

[Thorfun]

10 minutes ago, Oz07 said:

I'm also terrible at wet trades. I think a lot of the skill is getting consistentcy of the mix right whether it be mortar, adhesive etc etc

I did wonder if the adhesive was too wet but if I added any more then I think it would've been too dry. I guess it's a fine line. 

 

probably didn't help that I was trying my first attempt around a door in a constricted area up a ladder with cables in the way and needing to bring the plasterboard out 35mm. maybe if it was a flat large wall and simpler I might have had more success. but it's most definitely once bitten twice shy! especially when metal framing is so simple.

[-rick-]

13 minutes ago, Thorfun said:

probably didn't help that I was trying my first attempt around a door in a constricted area up a ladder with cables in the way and needing to bring the plasterboard out 35mm.

 

Really set yourself up for success there!

 

Curious why you even went down this route when you are already plasterboarding some walls?

[Oz07]

42 minutes ago, Thorfun said:

I did wonder if the adhesive was too wet but if I added any more then I think it would've been too dry. I guess it's a fine line. 

 

probably didn't help that I was trying my first attempt around a door in a constricted area up a ladder with cables in the way and needing to bring the plasterboard out 35mm. maybe if it was a flat large wall and simpler I might have had more success. but it's most definitely once bitten twice shy! especially when metal framing is so simple.

Yeh I've seen site bashers literally use a garden fork and spade to mix it up in a big tub. I think as dry as you can have it while still workable for board adhesive. 

[Nickfromwales]

1 hour ago, Thorfun said:

and needing to bring the plasterboard out 35mm.

If you’d have said that earlier, I’d have said don’t dab!

 

Metal frame saves the day (or timber) at that depth. 

[Thorfun]

1 hour ago, -rick- said:

 

Really set yourself up for success there!

 

Curious why you even went down this route when you are already plasterboarding some walls?

Curiosity? To see if I can do dot and dab. Also there was a bit in the cupboard that would’ve been a pain to use MF so I thought I’d give it a go. 

[Thorfun]

42 minutes ago, Nickfromwales said:

If you’d have said that earlier, I’d have said don’t dab!

 

Metal frame saves the day (or timber) at that depth. 

You live and you learn.