Building Homes or Extensions/OSB under siding / Adding stone veneer
QUESTION: Hello Bruce,
I have 2 questions. The first relates to how my house was built without any "house wrap" under the cedar siding. This house was built in 1991 and I bought it in 2001 from the original owner. Since buying it I have noticed they took a lot of shortcuts during the building of the house. The lack of a weather barrier is just one of them. My question is what are the consequences of not having any weather barrier under the siding? Can it create mold?
My second question is about adding a stone veneer from the ground halfway up the exterior walls. Is there a set standard for how high a half brick or stone wall should be? I live in a very rural area so I think this would really help it blend in to the scenery.
ANSWER: Hi Gary, house wraps weren't as common in the 90's as they are today. Back then it was standard practice to use felt paper as a barrier under shake and shingle siding. Usually it was a 16" wide strip layered up with each row of shingles similar to a roof with the bottom row going on first and each consecutive row overlapping the next. However sometimes it was regular 36" wide 15# felt installed first over the whole,wall and the shingles installed after. It sounds like you have neither method. The good news is that shingles allow the wall to breathe and short of a driving rain event the shingles should drain properly and allow the wall to dry out and hopefully avoid mold issues. There are sealers and mold prevention sprays that can help keep mold from growing and water from penetrating through the wood shingles so if you see any indication of bacterial growth you do have some weapons in your arsenal. It's probably not a bad idea to seal the shingles every few years as a maintenance habit. Thompson Water Seal is a simple product to use and not super expensive..follow manufacturers instructions for best results.
As far as adding a brick or stone wainscoting on the exterior you normally set the height around 40-48" depending on where the natural coursing ends up. In other words you don't want to pick an arbitrary elevation and then end up ripping an entire course of brick or stone down to meet that elevation. But you can go higher than that if you want to 5 or 6 feet even..there is no set rule. Since you have stated you don't think there is any felt or wrap behind the shingles you will probably want to take an extra row of shingles off above where your wainscot elevation terminates. Install a flashing over your wainscot and up the wall, seal that flashing with silicone or urethane caulking and then reinstall your shingles. This will help,keep water from getting behind your stone work. Be sure to follow your stone manufacturers instructions regarding vapor barrier and stone attachment. Some require a layer of expanded metal lath to be installed over the vapor barrier prior to the stone or brick attachment. You will also want to install a "weep screed" along the bottom of your stone to allow any moisture that gets behind the stone to weep out. Again this may or may not be a manufacturers requirement depending on the type of stone, cultured stone or brick veneer you are using.
I hope this information is helpful, please feel free to write again as needed regarding this or other matters, sincerely, Bruce E. Johnson, bejohnsonconsulting.com
---------- FOLLOW-UP ----------
Thanks very much for the quick response. I wanted to write a Followup to your comments. My cedar siding is not shingles or shakes, it is regular siding boards. Not that it makes a difference, as the OSB board underneath still needs some type of waterproofing. My house is a single story, ranch-style A-frame and has 4 gables, so to take all the siding off to add house wrap or waterproofing would be a major job. The east and south facing exterior siding is weathered and needs to be refinished and coated with protectant. The previous home owners used Sikkens Polyurethane and in many places it has begun to peel. So that project has been on my to-do list for quite some time. Do you think pressure washing would be a good idea? Or hand sanding? Some of the cedar siding has become black from the weathering.
I appreciate the advice on the stone wainscoting. I do have one more question pertaining to this subject. Right now, the cedar siding stops about 2 cinder blocks (foundation) from the ground. Should the stone wainscoting begin at ground level, or how far up on the block foundation would you recommend starting?
Thanks again for your advice.
Hi again Gary, sorry about the mix up on the siding type. But that's a good thing! Fewer entry points for moisture on lap siding. If it is a ship lap that is even better or is it beveled lap siding? Either way it's still better than shingles. At this point pressure washing may not be a good idea because it could force water behind the siding. If it is done carefully making sure the water pressure is downward and doesn't shoot up the lap it can be done. I am a big proponent of Clorox Outdoor bleach for troublesome mildew areas. I put it in an old house wash bottle that hooks up to a hose and meters the solution with water. I soak the area and let it sit ten minutes before rinsing it off, that might help the black areas. Otherwise since it has been sealed and you have peeling, sanding is probably your best bet for removing old polyurethane. If the peeling isn't too pervasive you might try some steel wool and mineral spirits. The mineral spirits will loosen the poly and the steel wool will smooth it out. But a good sealant after cleaning should help keep your sub sheathing osb dry. As will making sure all joints and junctures are caulked and sealed properly.
As far as your stone work goes, it is generally a good idea to keep your veneer work a minimum of 8" above grade. This will discourage any bugs and termites from trying to get under and at your framing.