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# Posted: 18 Sep 2023 12:37

I'm getting ready to install the Alure fiber cement siding on our new home. 7" reveal. The frame is 2x6 with 1/2" cdx plywood. Tyvex over the plywood.
My question is. Do I need a rainwall behind the siding ? On the sides of the home we have a 6' overhang so no moisture penitration issues there. The end gable walls have a 2' overhang.
There is no code in our area but home is built to meet all code requirements. And it is not needed in the city either.
That said I do like to do the best I can. My thoughts are that having the siding directly on the plywood is better. More rigidity.
Our climate is generally very dry. Long cold winters so average humidity is low. We are not in a windy area either.
Also I have read the install a strip of tar paper behind the joints. Sounds like a good idea but is there a better product ?
Thanks folks

# Posted: 18 Sep 2023 15:05 - Edited by: ICC

I like rain wall design for lap siding. That said, if you don't have much rain and have huge roof overhangs, then why bother? However, there is one further possible advantage for having a rainwall. That is when sheets of foil faced sheathing panels or insulation are used as the final wall layer. Then the 1 inch vertical furring strips space the lap siding out and create an air space. The foil plus the air space can up the effective R-value of the wall.

I also like the rainwall technique because then when, or if, water does get under the siding it dries out faster.

(My home walls have foam insulation sheets over the OSB sheathing with the final insulation layer being 1/2" foam with foil facing. The joints are all taped)

Siding installed on furring strips like that will have a nailing schedule supplied by the siding manufacturer. Follow the engineered data sheets for how many of what size fasteners to use to secure the furring strips to the framing and all will be well. I believe Fastenmaster has charts available for their screws and different types (weights) of lap siding

The rainwall technique also requires proper insect-proof venting strips, top and bottom.

# Posted: 18 Sep 2023 17:48


# Posted: 18 Sep 2023 20:39

Yes, a breathable vapor barrier is what I'd use. I redid a home with lap siding over OSB and it used tyvek under it.

# Posted: 4 Nov 2023 20:40

It sounds like you are all set to just put up furring strips (should those be pres-treated?) and apply the siding; with the aforementioned insect venting.

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