New construction technique on an old stud wall?
The clapboard on the west side of an 1898 house I own is suffering ‘iron rot’, what a carpenter friend of mine called decay of the ends of the clapboards around rusting nails. One way of addressing this is to remove all the clapboards, cut off the rotten ends, and re-install them, with new clapboard milled to make up the loss of the rotten portion. My carpenter, however, suggested first nailing up plywood sheets and a moisture barrier over the old balloon-frame studs before re-installing the clapboard. I completely restored the house in 2001 with wet-blown cellulose in the stud bays from the inside before the installation of new drywall, with no moisture barrier. A moisture barrier, I had read, was unnecessary with wet-blown cellulose since it is as dense as it was ever going to get and would not sag if moisture condensed on it exiting the walls in the winter. I have not had any obvious problems with moisture. I did have a paint-peeling problem which I solved by removing all the old paint before repainting the old clapboard (for the third time), based on a recommendation in an article in Fine Homebuilding.
My question is ‘Is there some benefit to adding plywood (or some other) sheeting and a moisture barrier to an old stud wall?’.
Replies
Unless you live in the South you should not apply a VAPOR barrier to the outside of a wall. You might (or might not) wish to install a rain-shedding barrier such as Tyvek or Typar. This is sometimes referred to as a "moisture barrier", but it is entirely different from a "vapor barrier" (or "vapor retarder", if you insist on the PC term).
The OSB would provide some additional wall stiffness, plus some wind resistance. The Tyvek (or whatever), in addition to shedding rain that gets through the siding, adds considerable wind resistance. However, in theory your wet cells should have considerable wind resistance already -- if you don't crack it too much while reworking the siding.
(My take is that Tyvek is cheap and easy to install and is a no-brainer. OSB is more complex and expensive, but might make it easier to reuse the short lengths of recycled siding.)
Response
Good suggestions. Thanks for your help.
rusty nails are the result of a moisture problem
If your siding nails are rusting that badly, then you do have an obvious problem with moisture. IMO, you should determine what it is before devising a plan on action for re-installing your siding.
sure it will add to the rigidity of the structucre vs not having it. Unless your going to do this to all your walls then you are wasting your time and money, plus your going to run into some issues. All window and doors, all your corners and details like these will now have to be addressed, corners changed and you still have only added rigidity to a building that has been standing for over 100 yrs...i understand your carpenters suggestions, but how does that address the (i assume) reason he is there, repairing siding.
The rusty nails were caused by decades of no vapor barrier and no insulation at all, combined with oil-based paints. Buckets of moisture condensed on the cold nails, rotting out the claps and likely some of the framing.
Of course, it's highly questionable whether it's true that no vapor barrier is needed with the cellulose, but the damage occurred well before that condition occurred.
That was why I said "made
That was why I said "made worse" implying that the walls had always been wet, which is the norm for walls from that era
It's unlikely that the wall has been made worse. Simply by reducing air infiltration the moisture problem will be significantly reduced, and so long as the exterior paint is not a vapor barrier (like the old oil stuff) it's likely that a "balance" of moisture in/moisture out will be achieved that won't be terribly bad. Not great, but not nearly as bad as before.
The only worrisome factor is that the cellulose will absorb moisture and hold it in place, vs having it simply run down to the bottom of the cavity and leak out.
And..
If I'm seeing this picture right it looks lke there is almost zero roof overhang which can't be helping any moisture issues possibly made worse by adding insulation.
Paint issue
The paint failure was a very interesting problem in that it did not occur everywhere. I do have a wet basement (with a sump) which lead everyone I talked with to conclude that it was an interior moisture problem pushing the paint off. if that were the case, though, it would have happened everywhere. In this case, there was significant paint peeling down to the wood only on old clapboard and only on the east and west sides. Specifically, the new clapboard facing east on the first room (the house is three rooms deep) had no paint failure. The old clapboard facing east on the second and third rooms had significant failure. The old clapboard facing south but underneath porches had no failure. The new clapboard facing south on the back of the first room/third storey had no paint failure. The old clapboard facing west on all three rooms had significant failure. The old clapboard facing west on the porch privacy wall (clapboard on both sides) had no failure. The old clapboard facing north had minimal failure. Only after I read an article in FH about paint shaving did I understand what was happening:
When paint gets old, it gets brittle. When the wood heats up and cools down, it expands and contracts. Old paint, having lost its elasticity, will crack with the expansion. It will still hold onto the wood, however, but when new, elastic, paint covers it and has a death grip on it, the expansion will result in the new paint expanding and pulling the old paint off. This phenomenon will occur on old clapboard subjected to the greatest heating by the sun - the east, south, and west sides. It explained why there was no paint failure on new clapboard on the east and south sides, and only minimal failure on the old clapboard on the north side. The porches shielded the south-facing old clapboard from the sun and were, thus, spared from the effect. It took me longer to come up with a reason for the lack of paint failure on the old clapboard on the west side of the privacy wall: The old clapboard on the hollow privacy wall absorbed the same amount of heat as the clapboard with insulation behind it, but the heat was conducted through to the air in the wall cavity and out through the clapboard on the porch side with little temperature increase and resultant expansion. The heat absorbed by the clapboard with insulation behind it was not conducted through, but instead, resulted in raising the temperature of the wood and expanding the clapboard.
think again
NKyriazi wrote:
When the wood heats up and cools down, it expands and contracts.
No, it doesn't. Wood expands and contracts with changes in moisture content, not with changes in temperature. Also, most peeling paint is a result of vapor drive to the exterior. This phenomena does has a correlation to direct solar exposure, but your diagnosis of your home's ailment falls short in the building science department.
I think you should read some articles on vapor drive (as it relates to building science) to actually understand why your paint is peeling because you've missed the mark here. IMO you've gone over the edge of reporting anecdotal evidence with commentary that supports a false conclusion presented as fact which, in turn, results in nothing more than the dissemination of misinformation. I don't believe there is a place for that in any forum.
deadnuts,
NKyriazi was right on the money with his analysis. Heat and cold do have an impact on the clapboards and
their ability to hold paint, as well it has an impact on the paints ability to keep its hold on the clapboard.
The type of paint (oil vs. latex), the age of the clapboards,and the age of the paint on the materials
at the time of re-painting also has an impact, all of which you will learn in time, as you gain more
experience.
Geoff
good luck trying to reason.
of course the change in outside temperature has a direct correlation to the problem the OP is experiencing. the change in temperature (ex. summer time- 90 during the day 65 at night) can change the Oh so beloved relative humidity this guy loves to reference by 20-35%.
the new one (must have just read an article about it) he is blasting -vapor drive- is also almost solely affected by heat/cold.
as a matter of fact the vapor drive he is trying to lecture on would have been decreased when the Op renovated and increased his walls R values.
122 still shooting from the hip
mark122 wrote:
as a matter of fact the vapor drive he is trying to lecture on would have been decreased when the Op renovated and increased his walls R values.
If this is a "matter of fact", then explain why professor.
ONE of the reasons why you are unbareable is you cant have a discussion without making it a pissin match, attempting to let everyone know what a smart guy you think you are.
this first one is probablly on the top of your reading comprehention level, the second one you may need a dictionary...either way, Ill let you read something other than the back side of a port a potty door for your source of information.
http://web.stanford.edu/group/narratives/classes/08-09/CEE215/ReferenceLibrary/Moisture%20Control/Water%20Vapor%20Migration%20and%20Condensation%20Control%20in%20Buildings.pdf
http://web.ornl.gov/sci/roofs+walls/staff/papers/143.pdf
Ill let you send these publishers letters pissin and moaning about how they should consult you before they publish anything else or request they prove theirs sources.
Oh, and just to show that you are a hack regurgitating (and in your own words disseminating misinformation) you say:
"Vapor drive can move this moiture toward the outside, particularly where and when direct solar exposure is prevelent. "
REALLY!!!! goodness man. When the temperature outside is greater than the temperature inside the transfer is the complete reverse of what you are saying.
The vapor migration is from the interior to the exterior in cold temps when the interior is warmer than the outside.
geez!
So you've learned to cut and paste links from your google search engine. Good boy. Now learn how to read them.
The issue is film finish failure due to wood fiber expansion and contraction (due to changes wood moisture content) which is being facilitated by vapor drive.
It should be noted that major cause of paint failure is exposure to UV rays and the subsequent breakdown of the paint resins that hold it together. This effect is most pronounced, obviously, on the sides facing the sun.
I doubt it.
Dan, is this one of your wild opinions or a fact based on qualified, independent research? If the latter, please cite your source.
In my opinion, the major cause (by far) of paint failure is poor paint prep work. I'd follow that guess with: problematic moisture issues related to vapor drive.
Break down of paint resin due to UV exposure is not really "failure" per say. It is the natural aging process of any manufactured material left exposed to the elements. In fact, I would argue that by the time this type of natural process takes place, any manufacturer or installer warranty would long be expired. The same arguement Dan makes for paint can be applied to asphalt roofing shingles. If 20 yr shingles start breaking down due to UV exposure after 20 years, then have they "failed". Not really; they simply have outlived their lifespan and need to be replaced. If you're dead set on calling it failure, than at least address the O.P.'s issue for the type of failure we're really talking about here: premature failure.
finefinish wrote:
Hi Dan,
If you slow air leakage you often slow moisture accumulation in the wall. I just know from experience (seen it dozens of times) that cellulose blown in to leaky old houses prevents drying/draining.
Not always.
It depends on the what is used in the wall cavity to insulate. Cellulose (wood pulp) is extremely hygroscopic. It is also air permeable. While its mass does slow down the speed at which air can pass thorugh the cavity and it can, however, act as a moisture "bank" for slow moving, moist air thereby increasing the R.H. in the cavity. Vapor drive can move this moiture toward the outside, particularly where and when direct solar exposure is prevelent. If the siding is film sealed it will easily lift the film from the wood surface. That's because the bond has already been compromised by changes in wood siding moisture content; not temperature. This is also why siding should be backprimed and lap joints left unsealed or uncaulked. This will more readily allow that moisture bank to dissapate. Many uneducated painters will caulk these clapboard joints in order to make a "failed" paint job look better when they re-coat. Good painters, on the other hand, will cut this cut this caulk or paint film joint by actuallly driving small wedges between the joints for an evenly spaced, open joint that facilitates air flow. Good painters recognize the problems associated with vapor drive in older, poorly insulated homes.Venting siding will not cure the problem, but it won't excerbate it. If a new home (or professionally re-modeled home) is propertly insulated and air sealed then moisture migration (due to vapor drive) will not be much of an issue and wedges are not necessary. However, wood clapboard lap joints should never be caulked or film sealed in any case.
Vapor Drive
numbnuts, I mean deadnuts,
from an article on the "Carlisle Coatings and Waterproofing" website published 03/13/2013 (www.carlisleccw.com)
"Vapor drive moves water vapor from areas of high density to low density"
" Moisture vapor will naturally move from the warm side of a wall to the cooler side."
" The movement of moisture via diffusion is a result of differences in vapor pressure that are related to the temperature and moisture content of the air. Temperature is the greater factor affecting vapor drive. "
" what this means is that vapor drive will act differently relative to a wall depending on the climate, or even the time of year."
Cold climate: vapor drive primarily from interior to exterior;
Mixed climate : vapor drive approximately equal in both directions ;
Hot, humid climate : vapor drive primarily exterior to interior. (Santos, 2007)
( note,highlights by the author, not myself )
simple, straightforward and to the point, no b.s.
your response to Dan was specious, at best.
Geoff
try understanding the information you're given
Nothing specious about my comments. Instead of randomly copying and pasting information, you might want to try understanding it as well. As your sources point out, moisture moves from areas of high density (in this case within cellulose insulation) toward areas of low density (outside). Paint doesn't peel and blister because vapor drive is forcing the paint film into the wood fibers, knuckle head. It's being driven out. Oh yeah, that's right, you still think wood expands and contracts with changes in temperature because you've never quit the kool aid.
For the record, the O.P. states he lives in Pittsburgh PA. Last time I checked this north of the Mason Dixon line. That's why, if a vapor barrier is used on this project it should be installed on the conditioned side of the building envelope, not as paint film on the outside.
can you really not see anything he writes after you ignore him? what a great feature!
Just a title an an indication the message has been ignored. It would be nice if it was less, but that's sufficient for me.
not so
Finefinish,
As I read (and re-read) your position it is that cellulose slows moisture accumulation in the wall cavity. My position is not that it slows accumulation but rather slows movement of moisture through the wall cavity. The latter phenomena can actually increase moisture accumulation and is a totally different concept from what you postulated. The phemonmena I describe (and results) are predicated on the cirucumstances described by the O.P.
Cheers!
I appreciate and respect your attempts at clarifying your positon. However, it brings up a couple more questions.
1. Why would less moisture laden air "probably" be entering the wall cavity after the addition of cellulose insluation vs. before no insulation at all?
2. Why would I believe the original wall cavities (presumabaly empty of any insulation and air barrier) to be wet?
Personally, I believe the addition of a poor job of installing blown in cellulose started the moisture problems within this structure. It could have been exascerbated by possible caulking of clapboard lap joints at some point by a painter trying to fix a failed paint job. I certainly don't believe it had anything to do with oil vs. latex paint or wood siding expanding and contracting with temperature changes. Those are my opinions, as stated. However, I believe them to be supported by sound building and wood science as outlined earlier.
beliefs cont'd
finefinish wrote:
The rusting nails and rot are evidence of moisture issues. It is my belief, and yours I believe (not too sure of anything anymore), that installing cellulose, without curing the moisture issue, lead to the paint failure. The OP said the paint issue is fixed - I am guessing the symptons of the problem have been relieved, but not the problem itself.
We agree on you first sentence...and have since the beginning. After that, it's hard to say what "the moisture issue" definitively stems from. You'd have to study the home as a complete envelope including roof construction and room use. Apparently the house was "fully restored" 15 or so years ago. That gave me pause enough to refrain from jumping to some of the (IMO) erroneous assumptions Dan made. My replies are mostly in response to his (and your) assumptions. I also feel that 15 years is enough time for a moisture issue associated with a poor cellulose insulation job to adversely show on the siding and nails. If the moisture issue had been inherent to the original construction, I should think that the original siding nails couldn't have possibly lasted the first 100 years. Further, I believe 100 year, empty, barrier free stud cavities alllow for all kinds of air circulation and drying opportunites that can easily check potential moisture problems.
BTW, the low pitched roofs in the photos could also be (or have been in the past) suspect areas for bulk water problems. Who know what part they may have played in the O.P. concerns.
Reiteration
I reiterate what I said about the perplexing nature of the paint failure: It did not occur equally everywhere. Attached are photos showing the disparity. In the first photo, the front facade on the left (facing north) can be seen with minor paint failure as compared with the west side. The last clapboard section on the right is the hollow porch privacy wall. All of the clapboard is old. The second photo shows two sections of the east side with the old clapboard on the left and the new clapboard on the right. The third photo is a close-up showing the paint failure occurring on the sections of old paint. The fourth photo shows the SE corner of the house with the east-facing clapboard on the right and the south-facing clapboard on the left, but under the porch roof. The fifth photo shows the SW corner and the clapboard under the porch versus the west side of the hollow porch privacy wall showing no paint failure versus the west-facing clapboard with insulation behind it.
Also, the wet-blown cellulose was installed from the interior with completely open wall cavities.
Understand that the pattern of failure may reflect many variables. What goes on inside a room affects the amount of moisture being "driven" outward, and if the previous coat of paint failed miserably and has been, some time in the past, completely scraped and repainted it may appear better than a section that did not fail so badly.