Help with Dot 'n Dab..


Postby diyjan » Thu Sep 11, 2008 1:44 pm

Hi there,
Could anyone let me know if the bare brick walls have to be completely clear of old plaster etc before we d n d? We have stripped a load of old plaster and plasterboard off our living room wall but the old stuff is a nightmare to get off.. Any help would be great!
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Postby kbrownie » Thu Sep 11, 2008 7:16 pm

Hi,
I'd recommend knocking off any old plaster if your dot'n'dabbing, as old plaster could be crumbling or loose, if you apply dabs on to these areas this is what is holding your board to wall. As the board will and extra to weight to this surface this could cause more stress to these loose, crumbling areas. It would not be an ideal surface to apply to,
I know it's a messy job (knocking off) but a job worth doing!
Kind Regards and good luck with project.
KB
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Postby ricky68 » Sun Sep 21, 2008 8:59 pm

[quote="kbrownie"]Hi,
I'd recommend knocking off any old plaster if your dot'n'dabbing, as old plaster could be crumbling or loose, if you apply dabs on to these areas this is what is holding your board to wall. As the board will and extra to weight to this surface this could cause more stress to these loose, crumbling areas. It would not be an ideal surface to apply to,
I know it's a messy job (knocking off) but a job worth doing!
Kind Regards and good luck with project.
KB[/quote]
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Postby ricky68 » Sun Sep 21, 2008 9:02 pm

[quote="diyjan"]Hi there,
Could anyone let me know if the bare brick walls have to be completely clear of old plaster etc before we d n d? We have stripped a load of old plaster and plasterboard off our living room wall but the old stuff is a ni
ghtmare to get off.. Any help would be great![/quote]


if you take of the old plastermake sure you stiff brush down the walls and PVA the walls
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Postby Bedders » Fri Sep 26, 2008 8:38 am

I've had extensive experience of this as a DIY'er (done 6 rooms in my house so far as old horsehair 1930's bonded plaster is falling away) & to be honest if you want a good job THAT WILL LAST i'd do the follwing.

1. Get all the loose old plaster off the walls. (If you've lots consider hiring or purchasing an SDS drill with chuck stop which allows you to use a chisel attachment. This is great for the walls. Chip off a bit with a bolster chisel & then get the drill behind the plaster at a steep angle & it will whip it off believe me. It will create a lot of dust so tape up the door on the inside & wear safety gear mask, goggles etc)
2. Once the walls are clear right up to the ceiling you'll be able to see the ceiling joists (just). You can mark up the lines where the joists are from one side of the ceiling to the other. Use small plasteboards (Baseboards) over the old ceiling if it is flat & clean (wouln't take down an old ceiling unless really must- board over) in a staggered brick fashion screwed with dry lining screws about 42mm long. That should be long enough to go through new board & old ceiling. Be careful around light fitting on ceiling!
3. Back to walls. Sweep with a yard brush & use dilute PVA building glue / Unibond to seal the walls of the old dusty plaster. Repoint if any chunks of gobbo missing. Wickes do a bag of ready mixed motar (in yellow bag might be blue cirlce) all you do is add the water and mix (no mixing seperate sand & cement & ensuring uniformity)
4. Dot & dab when gobo dry or avoid areas for dabs where youve gobbo'd up. You need to mix the bonding compound so that it is really, & I mean really, stiff but just moist.
5. Stick on boards & use a long flat length of timber to tap the boards to the dabs.
6. Leave to dry a day or 2.
7. Use fibre glass reinforcement tape to join board to board or board to existing sound plaster. It's self adhesive. Wouldn't use cotton scrim as it's too much hassle for a diyer.
5. I use jointing compound from Wickes to fill over the taped gaps as it has a little lime in the mix which allows for settlement. You can get your plasterer to plaster after the taping process (ie plaster the boards & your taped gaps) but modern plaster is cement based & once dry it may shrink a little when settling, & you may see hairline cracks on the joints.
6. Seal the joints with PVA if you've used jointing compound. Slap it on over the reinfocing tape & joint filler to seal any dustyness.
7. Phone you plasterer to plaster up.

Note you can cut corners but you'll be going back to rectify it later. Do it correct & it'll be fien for years!

Good Luck
Steve
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