We have very high cathedral ceilings which therefore have very tight angles where the walls meet the ceilings (around 45 degrees) how can we join these? The trowel won’t reach the tight angle

  • What kind of wall covering material are you applying? Drywall? Plaster? Something else?
    – FreeMan
    Feb 24, 2021 at 12:48
  • Could you provide a photo, on joints less than 90 degrees I normally use a wide knife and work away from the corner but these are rare so a photo would be helpful to understand why a mud knife won’t work.
    – Ed Beal
    Feb 24, 2021 at 14:56
  • Rather than trying to get a sharp acute corner, consider working with plaster's strong points and "coving" the joint (smooth radius somewhat away from the "point" of the corner.)
    – Ecnerwal
    Mar 26, 2021 at 13:54

1 Answer 1


This is plaster not drywall, correct? You do not use drywall techniques on plaster. Drywall the point is to get the mud flat to the board. Plaster is sculpted not drywall mudded. Here's a post from Fine Homebuilding on how to do it:

You get each wall plane flat. We snap a vertical chalk line near the edge on one side and use it as a guide to straighten (flatten) the other side. Once that side is plastered, we snap a line on the other side and plaster to it. Though all purpose mud could never go on thick enough to accomplish this, you could use durabond mixed thickly to make up most of the thickness and later finish with regular joint compound. We often plumb the walls as well. Skim coat plasterers much like drywall tapers do little to straighten anything. Veneer plaster works best going on thin and compound is extremely thin. We often plaster over blueboard with a base coat and then use a lime and gauge finish which can go on heavier than veneer finish plaster. We plaster in three dimensions, vice two. In quality construction, it is expected.

Good luck. If you have never done plaster and have a drywall background you are in for a surprise I think.

PS you can disregard this if you are one of those folks that uses the word "plaster" when you mean "drywall". Although, google up the thread on Fine Homebuilding since most of the discussion is about joining drywall at a 45, not plaster. Most of it is inapplicable to plaster of course.

  • Attributions should contain links to the source, not instructions to "Google up".
    – isherwood
    Mar 26, 2021 at 13:12

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