I seem to have made a mistake laying wonderboard my first time. I didn't stagger the joints and now I have a "hump" where four corners meet. What can I do to fix it?

I think I figured it out... I pulled up one piece of wonderboard that seemed to be the problem and replaced it... problem solved. Must have been a small piece of the concrete from the wonderboard under the corner. Yes... I'm female, and blonde... but I did figure it out!

Glad you figured this out. The 4 seams did cause the lump as you found. It is an error but not fatal. Tape your seams with fiberglass tape and then mud them in with a modified thinset. What kind of floor will you install?

I'm hoping you don't have an even bigger mistake. Did you use thinset under the wonderboard? I'm thinking you did not and that is an incredibly enormous mistake that can kill an entire installation.

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Originally Posted by cisboombah

I think I figured it out.... I pulled up one piece of wonderboard that seemed to be the problem and replaced it..... problem solved. Must have been a small piece of the concrete from the wonderboard under the corner. Yes.... I'm female, and blonde.....but I did figure it out!

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That's wonderful!!

Thanks for everyone's help. I finished my project and it looks very professional! I laid ceramic tile over the wonderboard... all the grout lines are straight and all the tiles are flat. (BLJack: I did use thinset under the wonderboard). Next project: new quarterround... grrrr those miter cuts are going to kill me!