Sanding plaster wall before painting

Discussion in 'Painters' Talk' started by Theleman, Dec 15, 2017.

  1. Wayners

    Wayners Screwfix Select

    @DIYDave. Some Pva will reactivate with water which is what a plasterer will need.. The waterproof Pva doesn't reactivate and you can emulsion over this type and get away with it.. But a risk.That's why some say it's fine and others say it causes problems, as depends which you use. Cover stain has a 4-7 day cure but 2 days in a warm house is fine. BIN is mush faster. 1-3 days but a warm house overnight is fine I find.
     
  2. Theleman

    Theleman Active Member

    After filling in the holes, sanding, then does it need another undercoat / mist coat on whole wall?
     
  3. DIYDave.

    DIYDave. Screwfix Select


    Always best to mist coat the filler before topcoating

    Again the mist coat will show any imperfections in your filling prep that you may have missed - but ...... just all depends on how fussy you are and what your happy with as a final finish

    If you’ve got patches of filler all over the walls, may well be quicker to mist coat the lot, but no, not essential

    Just bear in mind where you’ve been sanding, you will have taken off the mist coat on good areas of the wall that surround the repairs

    So maybe, but it’s ur call, just hit the entire wall/s with another mist coat - don’t take long does it :)
     
  4. Theleman

    Theleman Active Member

    Yup true. I have been filling and sanding this afternoon, and it is looking a lot better already. It is just so dusty, and some part of the first mist coat was peeling off. And where the mist coat was bubbling up due to sanding, I was peeling them off.

    Dust was so bad, my throat was raw in 2-3 hours even with new mask on, and vacuuming the dust, it might have blocked the hose. The vacuum is not working very well soon after.

    Maybe have to go and buy Plaster dust vacuum? Titan ones seem getting good reviews.
     
  5. DIYDave.

    DIYDave. Screwfix Select


    Couple things don’t sound right here mate ....

    ‘Mist coat was peeling off’

    ‘Mist coat bubbling up’

    A mist coat won’t / shouldn’t behave like that if correct materials used

    Newly plastered wall / mist coat (simple plain non vinyl emulsion thinned with tap water)

    When sanding, and it sands down very easily with P120/180 paper, it will just turn into fine dust (as uv found) don’t understand why it’s peeling and bubbling !

    Peeling may be the pva. Stuff that peels off does it feel stretchy I wonder

    Most domestic vacuum cleaners have gone too high tech with multiple filters, ok for average household dust and pet hairs but soon get blocked with excessive building / decorating dust, then a pigs ear to clean out

    A simple yet effective hoover is the best for this type of work - good old Henry being one. Make sure you use a bag in there (some peeps don’t) and just a simple huge filter that sits on top that just needs a bang out every now and again. Nothing stupid and complicated and over engineered to get blocked. You see a lot of trades peeps with old Henry for that reason (and he has a great suck as well) :D
     
  6. KIAB

    KIAB Super Member

    Hire a dust extractor will be a M or H class machine.
     
  7. Theleman

    Theleman Active Member

    We got white undercoat paint from B&Q. It is mat finish, no glossy at all. I mixed it with tab water about 60:40.
    When sanding sheets go over the mist coat / undercoat, it doesn't become powder, but it peels off.
    So really I was only able to sand the fillers - they become powder when sanded down.
    Something wrong with the undercoat paint you reckon?

    Hoover we have is Dyson, and I never use it for cleaning plaster dust. Dyson is too dear for that.
    What we also have is cheap vacuum from co-op. Cannae recall the make, but it is not so good one.
    It used to play up, so I fixed it recently, but tonight it lost its suction after sucking all the plaster and filler dust on the staircase.

    There is a Titan vacuum for plaster dust in screwfix, and it is selling for 39.99 Thinking of getting it tomorrow.
    Old ones, I mean where can you buy the old ones?
     
  8. KIAB

    KIAB Super Member

  9. Theleman

    Theleman Active Member

    Not sure why PVA would have got into the plaster, unless maybe someone put another coat of PVA trying to put another coat of skim coat?
    Stabilishing solution? - is it normally used in plastering? Or is it just special case remedies for like this one?

    Yup, Screwfix carries Titan Wet & Dry Shop Vac for 39.99, and they seem getting excellent reviews. They are the vacs for plaster and builders dust & debris.
    https://www.screwfix.com/p/titan-ttb350vac-1300w-16ltr-wet-dry-vacuum-cleaner-240v/36516

    I might go and pick this up tonight, as my old VAX vac from co-op is not working anymore.
     
  10. KIAB

    KIAB Super Member

    Some plasterers have a fetish for pva,adding it to plaster,not needed,can cause so many problems, even when used for priming it can cause problems.

    Stabilishing solution can be used for many things & on many surfaces ,like when they are dusty, friable, it binds & seals the surface ready for a final finish like paint,wallpaper,etc.
     
    Theleman likes this.
  11. DIYDave.

    DIYDave. Screwfix Select

    The Titan wet and dry is a great hoover and especially when you look at the price. I’ve got one but never used wet ..... so far

    Fixing system for wheels is a bit flimsy and two of mine keep falling off so had to bodge a repair but, it’s made to a price

    Great suction and good length hose and selection of tools, will suck up dust and lumps of plaster (dry) and general building stuff without a problem

    Just when using for lots of dry dust, remove paper filter daily (approx) take outside and give a good brush out with a soft brush as filter does get clogged, spare filters are available but never needed to replace mine as keep it clean

    Another tip if like me,you like saving ££ ......... the paper dust bags, cut off the end where it’s glued together, fold over couple times and seal with 2 small bulldog clips

    If using mainly for dry dust, can reuse the bags many times with this method. I bought with the hoover spare pack of 5 bags but these will outlive me I recon :) good luck !
     
    Theleman likes this.
  12. Theleman

    Theleman Active Member

    Great info thank you. Screwfix has it for 25 quid for 4 ltrs bottle. Feel not cheap.
    https://www.screwfix.com/p/sandtex-...ilising-solution-4ltr/21100?_requestid=148246
     
  13. Theleman

    Theleman Active Member

    Great tips. Thank you.
    Haven't had vacuum with paper bags for long time. I think last time we used bag using vacuum was early 1990s.
    Titan must have brought them back with their new models?
     
  14. KIAB

    KIAB Super Member

  15. Thele, why do your walls look shiny in your photos? What sort of paint did you use for the mist coat?

    And when you now say you've bought 'undercoat', what do you mean?

    Only two types of paint should be used on bare plaster - normal MATT emulsion (slightly diluted) or proper bare plaster paint (usually ditto).

    When you sand the walls to remove bumps and peaks, the mist coat should sand smoothly too, 'feathering' nicely, without any issues - it shouldn't peel.
     
  16. Theleman

    Theleman Active Member

    £10 seems good price. How many ltrs are in the 406's can?
    Isn't Screwfix's price all same wherever you are in UK? We are in just outside of Edinburgh.
     
  17. Theleman

    Theleman Active Member

    Yes, now the paint my wife got from B&Q as undercoat seems suspicious. I will read the label properly later on, and see what it says.
    It sounds like it is some sort of glossy paint the way it is behaving under the sanding.
     
  18. KIAB

    KIAB Super Member

    It's a 5ltr can,used cans of it here to seal distemper walls & ceilings, Edinburgh is way off my patch, contact Everbuild they should have a list of stockist in Scotland for their proudcts.

    Even Ebay it's £11:45p a can, post free.

    http://www.ebay.co.uk/itm/Everbuild...hash=item4d3a881f0a:m:meqz2AetyP7bQqt5j7B_zLA
     
    Last edited: Dec 19, 2017
    Theleman likes this.
  19. Theleman

    Theleman Active Member

    wow 5 ltr can for £10. That makes sense. £25 for 4 ltr can is just sound like gold liquid, I wouldn't put that on the wall which will be painted on.
    Thanks for your info. cheers.
     
  20. KIAB

    KIAB Super Member

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice