Backplastering

[Jim Morrison]

I was inspecting a magnificent old house built in 1895 (1/4 sawn oak and maple flooring, paneling, railings, trim in nearly every one of the 11 rooms) the other day. I enjoyed every minute of the inspection -especially the fact that despite the fact that it was selling for $1.3 million, the current homeowner was still schlepping wooden storm windows and screens up and down every year. The guy's pushing 80!! Incidentally, those windows -even the curved ones- were as close to perfect as I've ever seen at that age. One of the curved windows was actually glazed with plexiglass, but they told me the old fella raised 13 kids in this house, so I imagine the curved panes got broken a time or two and he got tired of fixing them.

Anyway, the walls were backplastered and my client asked me what the purpose of this practice was. I told her that I've always assumed it was to minimize drafts, but I can't say for sure because I've never researched it.

What do you say Bill? What was the intent of those hearty backplasterers?

[Steve Knight]

Jim,

My understanding is the same as yours, backplastering was done to prevent air infiltration. Typically it was done on high end homes. The Center for Integrated Housing at Virgina Tech has published a timeline for housing in the United States. Based on their timeline, the practice of backplastering was common until after WWII. You can find the timeline at http://www.cish.vt.edu/img/timeline.pdf

[Brian G]

I'm jealous as hell. I haven't had anything older than 54 years in months, it's depressing. I need my oldie fix, dang it! [:-weepn]

Brian G.

[chrisprickett]

In my day, a "backplaster" was a remedy for Lumbago!

[Bill Kibbel]

Jim,

I agree with you and Steve but I rarely encounter it. I don't think it was common practice here until the twenties. Could it be possible that it had been applied after original construction?

This is the youngest home I have inspected in recent memory.

The "Hall" of a 1928, 25,000 sq. ft. residence FD820026.JPG

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[Chad Fabry]

Ok Bill,

If I say I'd come work for you cheap, would you need any help?

[Jim Morrison]

Bill,

I suppose anything is possible, but I didn't see anything to suggest it was done after the original construction.

Appreciate the input,

[Rob Amaral]

Jim, I thought "backplastering" was what you did the next morning at the bar where you got hammered the night before... to get the 'hair of the dog that bit ya'...

[Chad Fabry]

I've seen back plastering done, but only if the finished side of the wall was wainscoting. Is that the set up in this house?

[kurt]

Energy efficiency was the primary concern. Somewhere alongside that was fire resistance. Backplastering was done in some instances as firestopping, or so I was told years ago. To that end, "backplaster" can often have asbestos fiber.

I also remember hearing one time that if a house is backplastered, one should not insulate the stud cavities as it will reduce the R value of the wall instead of increase it. Anyone else heard that?

[Chad Fabry]

Open stud cavities don't affect R value. But they affect insulative quality. Since R value is a measure of heat conductance only, the r value of any given assembly is relatively constant. But, that R4 interior wall is going to perform much much better if you can stop the convective currents within the stud cavity. Temperature differential has everything to do with insulative value and if you keep the temps in the stud cavity from being lowered by infiltration and convection, then you've increased insulative value. Air infiltration accounts for the largest portion of heating losses. Stop the air from moving. It's important.

[Steve Knight]

I used to own a home built in 1890. Exterior walls were backplastered. Walls were uninsulated when I bought the home. I blew cellulose into wall cavities. The only concern I had was trapping moisture in wall cavities. However, plaster will dry to outside, so I decided the insulation would not hurt. It sure helped my heating bills.

The builder of the home must have been very concerned about fires. Exterior walls were from inside out were 2x4 with ship lap sheathing. Building paper was installed over the sheathing and 1x2 were installed over building paper, then ship lap sheathing then asbesots paper and finally cedar clapboard.

The insulator I hired almost went nuts trying to drill into wall cavities. To make matters worse, the house was ballon framed and had fire blocking installed every four feet in every stud cavity.

[Jim Morrison]

Note to TIJ readers: For those of you who don't already know, a long time before Rob Amaral became one of US Inspect's favorite sons, he spent several years as one of the front men (playing some slick-ass guitar) for the Boston area Rock 'n Roll band The Lifters. I believe his posts may be better understood in that light. (Summary: He's slightly off)

Anyway, the interior of these walls were mostly plastered, but there was a lot of wainscoting, 1/4 sawn oak paneling, and 1/4 sawn floor to ceiling built in bookshelves on the first floor.

I liked it so much, I thought I'd look around a little and see if I couldn't pick one up for myself. [] Pretty soon, you won't be able to find one like it for under $2 million....

[kurt]

Originally posted by Chad Fabry

Open stud cavities don't affect R value. But they affect insulative quality. Since R value is a measure of heat conductance only, the r value of any given assembly is relatively constant. But, that R4 interior wall is going to perform much much better if you can stop the convective currents within the stud cavity. Temperature differential has everything to do with insulative value and if you keep the temps in the stud cavity from being lowered by infiltration and convection, then you've increased insulative value. Air infiltration accounts for the largest portion of heating losses. Stop the air from moving. It's important.

I know that part; tightening the envelope is where energy efficiency (and condensation) begins, and certainly not where it ends. I grew up in a house built in 1857; I understand convective currents. I clearly remember waking up to ice crystals on the north wall of my BR about 8" from my head.

What I heard years ago (mid-70's in the first energy crisis) was that the backplaster was thermal mass; if you place thermal mass "outside" the insulation, it will function as a heat sink & "pull" heat out of the insulation. Not that I'm buying into this line of thought; it was just one of those memories that came to mind when I heard the term backplaster.

[Jim Morrison]

Originally posted by kurt

What I heard years ago (mid-70's in the first energy crisis) was...

There was an energy crisis in the '70's?!?!?

You'd think the FCC would have interrupted "Hong Kong Phooey" to alert the nation. Geez... You can't even trust the government anymore...Someone send me an IM when gasoline hits $2/gallon would ya?

[Chad Fabry]

Kurt, I knew you knew that. I thought it was a test.

[jak531]

I feel a little foolish, but what is "backplastering" and how do you recognize it? Thanks

[kurt]

Nothing foolish about asking questions.

Backplastering is the practice of plastering the *interior* side of exterior sheathing boards; basically, the stud cavity exterior wall is plastered.

[Bruce Thomas]

OK so I was hoping that someone else would ask this so I wouldn't have to look dumb. Would someone define what "back plastering" is and how it's installed. Please

Bruce

Never mind

[Chad Fabry]

http://www.historichomeworks.com/hhw/qa/qa10.htm

That's a reasonably good answer to your question, Bruce. It also goes on to explain the issues that insulating the cavities can create.

[crusty]

Originally posted by Jim Morrison

Someone send me an IM when gasoline hits $2/gallon would ya?

Unfortunately old news out here.[:-censore