Hanson Carlen Architects Spokane | Drainable House Wrap

Drainable House Wrap

February 05, 2015  •  Leave a Comment

One impressive new product manufactured for our specific climate is a drainable housewrap by Benjamin Obdyke.   The main idea of HydroGap is to make a water resistive barrier behind the siding that will allow any wind-driven rain or moisture that gets behind the siding to drain.  The way this product works is thousands of plastic nubbins gap the siding off the wall about 1/32 of an inch to allow water to drain downward and out at the bottom of the wall. 


When I starting working with my father in this business over 30 years ago, he and I were using 15lb felt paper behind the siding! This was before the word “housewrap” was coined.  Later, in the 1980s the trade went to various plastics and synthetic housewraps.  The two layers of  ‘tar paper’ (15lb felt paper) that dad and grandpa installed was most likely far superior to the synthetic wraps; this was because the first layer shrunk some and crinkled and was less of a water trap, which allowed the sheeting to dry.


A more robust method of doing the same thing is to build a rain screen which actually makes a ¾” gap + or – between the siding and the wall sheeting.   I think the full blown rain screen is overkill for our climate.   Spokane typically has a hot, arid climate during the summer months, bracketed by short spring and fall seasons. Unlike our neighbors in Seattle; they tend to get rain every two days all year long; whereas, our area has the chance to dry out.


Last week I drove by a typical Spokane new construction home and took snapshots of the typical “housewrap” job.   Bad product, bad installation, sorry homeowner!    


Hydrogap 1Hydrogap 1HydroGap a wrap that drains! Hydrogap 2Hydrogap 2One side done! Hydrogap 3Hydrogap 3Closeup of window. Note Vycorner (green thing) behind 3M 8067 tape Hydrogap 4Hydrogap 4Full Rainscreen method Hydro gap 5Hydro gap 5This is what a bad job looks like. Lets go back to 15b felt!

Here is what a bad job looks like!

Do you really save anything hiring a cheap builder?


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