Is 18mm plywood ok for a 230mm deep sofit?

[epsilonGreedy]

I ask because I have a 4x8 sheet left over and it is just enough to run under the wooden boxed eaves of my single storey utility extension.

 

The rafters are on 600mm centres.

[ToughButterCup]

My first thought was .... water. OSB3 therefore, or similar. Soffit board is commonly much thinner than 18mm, I understand

[epsilonGreedy]

15 minutes ago, ToughButterCup said:

My first thought was .... water. OSB3 therefore, or similar. Soffit board is commonly much thinner than 18mm, I understand

 

 

Hnmm even when painted OSB would look a bit rough.

 

I hope the underside of the eaves will not get wet too often. If done correctly I will have plastic eave trays over the top of the fascia with an angled flap directing run off water direct into the centre of the gutter. There will also be a 5 to 10mm recess along the bottom of the fascia up to the base of the soffit.

 

I am hoping that a thick soffit will allow for fewer screws to keep it tucked up and in place. I really don't want to look up in 5 years time and detect sag between the 600mm centres.

[tonyshouse]

Soffit boards should not get wet, 6mm ply would do so 18 will work,