Porch wall - wall board material options?

Henry W

Senior User
So I have a friend that wants a wall erected on the side of his back porch, primarily as wind and rain screen. Proposed wall is to be conventionally framed and sided, to match appearance with the house. Currently two of the four sides of the porch are open, with the back wall of the house and the sun room forming the 2 solid walls. The proposed third wall is to close in the side of the porch and will have Hardiplank siding on BOTH sides of the new wall. This wall will not be structural - just tying into the existing roof and the house wall.

Here's the question: What are the reasonable options for the type of wall board under the siding of the exterior of this wall? It has been years since I have done any 'framing' of exterior walls. Insulation is not important, but keeping water out would be. The plan is for conventional framing, wall board, house wrap, then siding. Is wall board needed here at all, or can the house wrap and siding simply be installed over the framing without any type of wall board? Interior side of the proposed wall would simply have siding installed over the framing.



Senior User
Install over plywood or OSB. OSB is cheap enough I would do it on both side.

If you install Hardieboard directly to studs, you will probably get some bowing (gee how do I know this LOL)

Hardie has installation info on their website here.


Corporate Member
The same sheathing/house wrap you use on the outside would be fine for the inside. I would definitely use OSB on both sides. Depending on type of porch/deck (concrete poured porch or wood deck) you may want to do a galvanized metal or rubber flashing at the bottom in case a driving rain pushes it in and may sit against the wall. This is standard when attaching the deck to the house. Even though the bottom plate will be treated if water sits for long periods of time it can still be a concern in the long run. I’ve done some like this in the past (albeit on new construction) and if sitting water is a concern at the new wall you could also put in a couple of weep holes at low spots to give it a place to drain as well. One other thing to think about if this is a wood deck is make sure the added weight of the wall, sheathing, and siding won’t add so much weight it overloads the existing deck posts.


Corporate Member
I re read the post and left a couple things out. I would use OSB for the sheathing and you do not need any additional wall board on top of that for the siding installation. DrBob is right about not attaching directly to studs. You will get pretty significant waves in the siding if you do it that way.

Phil S

Board of Directors, President
Phil Soper
Staff member
Corporate Member
Glass-mat sheathing, same as used on almost all commercial buildings. simple to install and you will never have to worry about mold and mildew.

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