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Plastering of 1940s semi

Discussion in 'Decorating and Painting' started by adam2, 12 May 2006.

  1. Third_Eye

    Third_Eye

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    Skimming over old plaster.............................
     
  2. adam2

    adam2

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    Oops...meant skimming over the old browning....

    The plaster which has now all fallen off has been there since the house was biult together with the browning. Is that reason enough to replace the browning since its old and has cracks in places. Is it still suitable to place new plaster over old browning stuck to brickwork? My colleague who is getting another plasterer in says that it can be plastered over.
     
  3. Third_Eye

    Third_Eye

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    The thing about Browning is it is very brittle and always will be. Yes, you can plaster over old Browning provided it is properly sealed, but if it can be broken with an dry paint brush then this usualy means its lost it's hold (but intepretations can vary). Basically its all down to cost whether to take off all old browning (costly) or to skim over browning (cheaper). To be honest in my own home i cut out a crack on a wall as it was browning and the browning was very brittle and i could have easily taken off all browning, but i decided not to and i sealed up and re-plastered which the walls are still perfect. To be honest if there are any cracks then the best thing to do is run some fiba tape along the cracks whilst plastering in order the cracks dont re-appear (assuming they are not structural cracks).
     
  4. adam2

    adam2

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    Since i bought the property i have always wondered about structural issues being an older house.

    Observations: the rear porch has slid away from property(was not attached). concrete slabs at rear of property moving away from brick will 1cm gap which needs filling. Cracks appear in browning ...more prominent near doorways...ie near frame supports and windows.

    However surveyor ruled out subsidence. the property is in clay soil area so heave tends to be more common in clay soils.

    I know not many people on this board are structural surveyors but what kind of cracks in plaster or in the property would suggest structural problems.
     
  5. JohnD

    JohnD

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    Ones that get bigger

    Ones that break the bricks instead of just the mortar between them

    Ones that run diagonally from the corners of doors and windows

    Ones that are clean inside (i.e. obviously fresh and new) on an old house

    Ones you can poke your finger into

    Ones that make anything lean (a wall or chimney)
     
  6. adam2

    adam2

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    Thanks John,

    none of those apply. the cracks are near the door frames and in window side frame areas and some also occur mid wall.

    back to plastering....

    after running around i found another plasterer. He's from the Czech republic and understands little english but seems to know the job.

    Anyway i explained the problem. He applied 1 in 5 or more dilute PVA from wickes..brushed on then applied plaster. His finish was much smoother and professional you could see it was done properly.

    Anyway behold within minutes when the plaster dried the cracks appeared. so he wetted the surface with more PVA mixture and water and reapplied. This helped but fine cracks still appeared.

    He explained to me in half Slovak lingo and English that the walls were sucking the water dry out of the plaster too quickly even with PVA.

    So he then used wickes bonding undercoat. He proposes to coat all walls with this allow to dry out then place fresh plaster on this. He says this should help the plaster stick and not crack.

    Anyway as he was doing it the bonding was starting to crack...he managed to get some of it fine/smooth...but its looking as if the walls won't accept any plaster. Our only hope is if the bonding overnight does not crack and then he can plaster over it. His finish is very smooth. He's in his forties and was plasterer back home...he certainly had the tools.
     
  7. Third_Eye

    Third_Eye

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    Sometimes you need to PVA three times over porous surfaces prior to applying plaster (A Pro Plasterer would know this) and allowing each coat to dry (apart from the last coat). Also if he applied one coat of 1 in 5 or more dilute PVA from wickes, then again this is not enough. This is why it is cracking.
     
  8. adam2

    adam2

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    I think the plasterer was not aware of the dryness of the wall so applied one coat.However when it started cracking he sprayed with water and allowed the wall to soak up more water prior to applying more plaster. This was after 5 mins after we noticed it start to crack. Where he did this the walls are not cracked. And the bonding undercoat is now intact with cracks only in deep areas(where larger holes were in browning) The plan is to use undercoat on all areas of wall, allow to dry then PVA wall and plaster over. I will speak to him to apply more PVA and more coats. Hopefully this will solve problem...if not then i think its back to the drawing board. What impress me is the finish that he seems to get compared to the other guy. I'm not giving up yet and would prefer to have plaster than buy plasterboards which have to be plastered anyway.
     
  9. JohnD

    JohnD

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    I'm no plasterer but can do patching and chases.

    When I had an old house plastered (mostly back to brick) the guys put on a thick backing coat (bonding or browning depending on the wall) which was devilled and cracked a bit as it dried, then came back the next day and put on a very thin layer of sirapite which they flicked with water and polished very smooth when it seemed dry. The cracks in the backing coat did not come through.

    Isn't that usual?


    (I will add that it's a pleasure to watch an experienced pro, both for speed and the startlingly flat and smooth surface)
     
  10. adam2

    adam2

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    Thats reassuring John.

    I was just wondering will the guy have to devill the bonding coat when its dried or can he apply plaster straight on...The browning was already devilled previously when we scraped off plaster as we found it. I'm sure he knows but i won't be there when he does it.....
     
  11. jbonding

    jbonding

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    this should of been done just as its going off or cracking (due to suction), this would of tied it back together and provided a key for the finish. Any plasterer would know this and i dont fancy your finish staying on and if he's relying on pva again tell him to forget it ;)
     
  12. adam2

    adam2

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    The browning had already been keyed heavily. The bonding undercoat was placed on this. The plaster was then applied on top.

    Have just seen the room today. Most of it was done in the morning and cracking usually appeared within 30 minutes if not earlier before.

    Well on first impressions there are no cracks. The finish is smooth and very level/straight. It looks like a professional job but will wait to judge on that.

    Near the window sills (the sides) where the plaster meets the window frame he spoke about wood or strip....not sure what he was talking about I think he means we should place new wood strip(vertical) to level finish off at this intersection..a bit confused what he means?

    The main problem was the suction..very dry wall needing lots of water. he ended up using a sweeping brush to appply PVA and water.

    He will start 2nd room in the morning.
     
  13. jbonding

    jbonding

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    This should of been keyed to take the finish. im not sure about around the windows but usually skim beads are applied.
     
  14. Third_Eye

    Third_Eye

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    "JohnD" of the way you explained anout patching, i know of many plasterers who have done this and the finish coat "fixes" the suction problem but one year later some patches can start to crack !
     
  15. adam2

    adam2

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    I'm not sure if he has keyed bonding or not. The plaster has been applied today so i can't see the bonding would have dried enough for key. However the plaster is sticking and is hard. What symptoms should i look for ..if the bonding wasn't key would the plaster stay up for long?
     
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