Our client has requested to change the exterior wall cladding from from smooth panel cement board to acrylic stucco mainly for aesthetic reasons (eliminates corner trims, battens, etc.). Woodpeckers are a real concern in the area and when they knock on stucco with foam behind it sounds hollow so they keep digging.

First up, the proposed wall assembly: (BC Interior Climate Zone 6)

5/8″ GWB
Membain vapour retarder
2×6″ Studs @ 24″ of
R22 Fiberglass Batt Insulation
3/8″ OSB Sheathing
Tyvek WRB
2 Layers of 1″ Type 2 EPS with staggered joints and taped seams on outside layer
1/2″ furring strips for Rain screen (mainly to allow wall cavity to breathe through EPS as we receive so little rain and very hot summers, also a means to attach foam though)

Here is where it gets tricky simply because of the woodpeckers…there are many drainage plane products (dimpled mats with adhered WRB, mesh like mats with WRB) that we could use as an alternative to wood furring strips however none of them would stop the hollow sound that the birds like and I would prefer to not have two WRB’s and want to keep the WRB over the sheathing. So we are considering (added costs and labour aside):

Option A – over wood furring strips
Cement backer board
Wire lath
Scratch coats
Final Coat

Option B – essentially the same but OSB rather than cement board as it will be slighty cheaper

This may seem like total overkill but we need to maintain a ventilated rain screen to allow the split wall assembly to dry to the exterior as well as the interior. Adding a hardboard backer ptovides a good consistent substrate to apply the stucco and although costly, should reduce the “hollow” cavity effect of the foam and ultimately prevent wood peckers from finding their way into the foam.

Thoughts are appreciated! And no we aren’t putting plastic owls on the eaves! Ha!

Brett Sichello