How to finish external join in 4.5mm fibre cement?

[trai]

I have raised the ceiling in our alfresco area, and swapped from a fibre cement sheet roof which used to be at the same height as the eaves, to a gyprock aquacheck material. Now I need to fit new eaves and then a vertical piece to come up to the new roof. My question is, do I have to use the pvc external joiners, or can I achieve a smooth external corner like you can with gyprock inside? Hopefully the picture i got from the web helps clarify my rambling and the join I'm talking about!

 

[EricL]

Hello @trai 

Welcome to the Bunnings Workshop community. It's sensational to have you join us, and thanks for sharing your question about the finish on your fibre cement board. 

In order to get a perfect finish, it is necessary to install the Siniat 30 x 2400mm 90° PVC External Angle Plaster Trim. It also protects the corner from bumps and hits should you accidentally walk into it with a tall ladder or piece of timber. The plaster trim also serves as reinforcement and as an expansion joint between the two boards. 

Here is a handy step-by-step guide: How to attach and plaster an external angle

If you have any other questions we can help with, please let us know.

Eric

[trai]

Hi Eric, I'm not sure those products are suitable for the fibre cement sheet? For some reason I feel like it's different to the paper on the internal gyprock sheets? 

[EricL]

Hello @trai 

My apologies you are absolutely correct, it is different with fibre cement. Please let us double check with our suppliers and we'll get back to you as soon as we have more information. 

Thank you for your patience.

Eric

[MitchellMc]

Hi @trai,

It's a very similar trim for fibre cement, such as the Siniat 2.5mm nib 32 x 3000mm PVC External Render Trim—32 x 3000mm 2.5mm or Siniat 55 x 2400mm Render Bead 2.5mm nib.

Here's a helpful guide: How to render corners.

Please let me know if you have any questions.

Mitchell

[trai]

Hi MitchellMc, thank you for your advice.  I tried rendering as per your suggestion,  but it just falls off the fibrecement sheet. It doesn't seem to work on the eaves. Bit of a mess really! I think the render is for brickwork.

[MitchellMc]

Did you install the render trim along the corner, @trai? It holds the render in position. Also, is the fibre cement painted?

Mitchell

[trai]

Hi,  yes.  I think I should have used gyprock base coat for fibre cement. https://www.bunnings.com.au/dunlop-3kg-fibre-cement-jointing-compound-3kg_p0088481

[MitchellMc]

Hi @trai,

What product are you using? If the sheets are painted then you would need to sand the paint of for either jointing compound or render to stick to them.

Mitchell

[Jewelleryrescue]

Hi @trai 

Looks like you allready fixed  all the sheeting so all you need  is a neat  corner like  gyprock.

I  would use Fibreglass builders tape.   tape 50mm  wide on the sheet  corner it  has adhesive and  will stick  over the corner and then  use your fibre cement joining  compound or  gyprock finishing compound and  sand it smooth once dry.

@MitchellMc  and  @EricL  recommended products  are good too if you need to do more sheeting.