High Suction Wall - What can i do?
- Thread starter ajrose16
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Your not prepping it correctly + Bonding plaster is for low suction backgrounds. You can still use it on high suction with the correct prep; you must PVA seal the day before & then PVA as normal imedietly before you plaster; build the base up in 2 thinner coats one after the other, not one thick coat.
What is it you’re trying to do?
What is it you’re trying to do?
I think richard means in the one visit to the wall for the undercoat. So the two coats go on staight away. one pass of the trowel at about half thickness over the wall then a second pass Don't try for full thickness in one pass of the trowel. Then use the long straight edge (darby) to leave the undercoat flat don't play with it too much!
If the undercoat needs to be more than 12/15mm you will need to dub out the the areas needing thick plaster before you put your final undercoat over the whole wall. The dubbed out areas are done a day before and allowed to set befor the normal/final undercoat goes on
The same goes for Skimming (the next day is often best) you whip a thin layer on to cover the work and then make a second pass to build up your skim to finish thickness of 2mm or 3mm Try to put it on in just one pass will give you trouble!
P.S. I can't use a darby freehand to save my life! - I have to set vertical battens on the wall at say 1.5m centres plumbed and lined through. put my two layers on the undercoat and pass the darby over two battens at a time to rule off flat between them - After inital plaster has set whip the battens off and fill with under coat. Slower but my oh my I get a really flat finish that my skim can follow! - Not necessary for patching work though
I would always skim it the same day if you can, otherwise you'll end up with another suction problem the next day, which requires more PVAing etc etc.
A darby is a great piece of kit Blag', if you can just get the hang of using it,,,, keep practicing. The one i have is made of yellow pine. It's lasted me for years, and it keeps it's shape perfectly,, (a bit like my wife really), bless her.
As RC; always skim plaster base the same day if you can, as soon as it’s set or all you’ll do is repeat your suction problems; only render base needs to be left.
Heck Guys, give me a chance! After I've done the undercoat I will be in no fit state to skim it, I'll be enjoying a nice cool beer while it sets. Strictly no site work after boozing
!Your right of course and I have always set out to skim as soon as I can. My failing for fogetting that because I do the jobs in the evening including all my own labouring I will be pushing it to get the skim on same day. Also learnt the hard way what happens if you do it too soon when it really has not set sufficiently!- After that I make damn sure its set with a days break and yes I may need to use my hand spray if its drying out quickly.
Never checked it but what is the typical set time (new stock!) three/four hours ?
I did say if you can but as long as you re-prep, it should be fine; just a bit more work.Heck Guys, give me a chance! After I've done the undercoat I will be in no fit state to skim it, I'll be enjoying a nice cool beer while it sets. Strictly no site work after boozing
A base coat should be ready to accept finish from around 1½-2 hours but it depends on suction.
Would temperature have an effect too?
I did a wall on Sunday which had a tight Bonding coat applied before skim. Must have taken 2.5hrs to go off enough. There's no rad in the room currently and it's a tad chilly in there!
As an aside, I find now I prefer to skim same day.
When I've put Bonding on and left until next day, I have found that even with wetting I've been getting suction problems.
Whether that's down to my particular house's blocks under the plaster who knows.
Cheers Richard, yes I appreciated the if you can bit. Alas for me it probably will never happen same day.
Now you have got me! - I never would have thought this would have any impact on the Set. - Would be interested to learn more especially as the short set time you have mentioned really does suprise me. Edit: And like the other post above I tend to use bonding more often due the nature of the backgrounds.
Now you have got me! - I never would have thought this would have any impact on the Set. - Would be interested to learn more especially as the short set time you have mentioned really does suprise me. Edit: And like the other post above I tend to use bonding more often due the nature of the backgrounds.
Yes definitely; ambient temperature & suction is what makes the stuff work.
I usually only use water for prepping blocks but if I have to leave the base coat, I re-prep with PVA mix not just water. Bonding is really only for low suction, it has good uses on crabby walls but I would not use it on new/good condition block walls; I have used Hardwall but now prefer to use good old fashioned render as a base.When I've put Bonding on and left until next day, I have found that even with wetting I've been getting suction problems.
Whether that's down to my particular house's blocks under the plaster who knows.
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When I use bonding I always put a good scoop of cement in with it when mixing , after you have done it a few times you will get to know the setting time and it will help you build out a lot quicker... Never had any bad results... Yet!!!!! Come on you "olduns" some of you must have used this old trick..
Come on you "olduns" some of you must have used this old trick..
once Roy...wouldn't consider myself old though, matter of opinion i suppose 
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