New siding, old building – process and underlayment
Okay here is the scoop. I have been hired to reside a 1750’s farm house with very small overhangs. It has flatsawn clapboards probably pine 50+ years old is my guess and trim that predates the siding. There is felt paper underlayment under everything that i can see. Large swaths of the siding and virtually all of the trim needs to be replaced so I recommended that the entire job be done for ease and continuity.
If money and time were no obstacle I would love to put a new roof on this house, extend the overhangs, put up a rain-screen with a modern underlayment air seal everything blah blah blah… But this job is just siding and trim.
So my questions are.
1.) Does it make sense to put house wrap up if i cant properly flash windows to it? If it does, should I use drainble house wrap? This is a product I have never used before and it seems kind of gimmicky. Does it work? Can and should I tape it to try to create some kind of air barrier? Everything else about this house is still in the 1700’s does it even make sense to start updating things like housewrap with out addressing other issues. My main concern being if I cant flash the windows and doors to the WRB properly and water gets behind the WRB am I actually limiting the ability of the wall to dry properly.
2.) The customer wants painted claps, so after calling around and seeing whats available in my area in price range these are the options.
Primed CVG finger jointed western red cedar – 1.05 lin/ft
Primed CVG Hemlock – .99 lin/ft
Primed Lifespan (oil primed treated clear pine) 1.38 lin/ft
Leaning tword the finger jointed cedar. Any advice or comments are appreciated. Thanks!
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Replies
Hi Seth.
Most WRBs are vapor-open and do not prevent the sheathing from drying. Benjamin Obdyke Hydrogap, for example is a 16 perm, drainable housewrap. While drainable WRBs do not give you the same benefits as a full rainscreen, they do allow for drainage and water trapped behind the siding is one of the reasons why WRBs fail and sheathing gets wet. Check out this article for more info on modern WRBs: Nine Water-Resistive Barriers Worth knowing About .
Does the house have sheathing beneath the felt? If so, you can air seal the sheathing in number of ways. If it is old board sheathing, you could use a self-adhered WRB. If it is updated to a sheet good, you could tape the seams. Both of these are better approaches for air sealing than trying to make a taped, mechanically fastened WRB work as an air barrier, thought that will still likely be an improvement over what you have.
If the existing felt is integrated with the windows and doors, you can leave enough of it around the windows and doors to integrate with the new WRB. You might find this helpful for ideas: Window Install BEFORE DuPont Tyvek Weather Barrier. I'd be curious to know what others have done in this situation.
If you go with a finger-jointed siding, be diligent about priming all sides before installation.