Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Building & Construction

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 11-13-2011, 07:36 AM   #1
Don't WANNA do it myself
 
mnp13's Avatar
 
Join Date: Jan 2007
Location: Rochester, NY Area
Posts: 626
Rewards Points: 0
Share |
Default

Plaster and lathe construction


I'm looking at insulation options for my attic. How much weight can the plaster and lathe support per square foot before I have to be concerned with it shifting / cracking / coming loose?

__________________
Michelle

Fixing the re-muddling one room at a time...
mnp13 is online now   Reply With Quote
Old 11-13-2011, 07:45 AM   #2
old guy contractor
 
tcleve4911's Avatar
 
Join Date: Nov 2010
Location: Maine on Little Sebago
Posts: 857
Rewards Points: 0
Default

Plaster and lathe construction


If it is old horse-hair plaster and lathe, it may crack just from you being up there.
If it is rock lathe, plenty strong, typically no problem.

The weight of fiberglass insulation should not be a problem

tcleve4911 is offline   Reply With Quote
Old 11-13-2011, 09:45 AM   #3
Don't WANNA do it myself
 
mnp13's Avatar
 
Join Date: Jan 2007
Location: Rochester, NY Area
Posts: 626
Rewards Points: 0
Default

Plaster and lathe construction


My joists are 2x12's they don't seem to notice my weight on them ( no creaking or noises.) I don't believe the plaster is horsehair, when I've worked with old plaster before i could actually see the hair in it.

I helped gut a building that had straw instead of lathe. THAT was a mess!!!!!

I'm not sure if I'm doing fiberglass or cellulose at this point. The big question is the load. My plaster is in decent shape for being 125 years old, though there are cracks there are very few loose sections. But that would quickly change if the lathe started moving!
__________________
Michelle

Fixing the re-muddling one room at a time...
mnp13 is online now   Reply With Quote
Old 11-13-2011, 08:11 PM   #4
Too Short? Cut it Again!
 
Join Date: Sep 2009
Posts: 9,635
Rewards Points: 0
Default

Plaster and lathe construction


Insulated many an old home with lathe and plaster ceilings and never had a problem. Obviously if you have substantial sags where the lathe may have failed that needs to be addressed.

If you are planning to blow the insulation in you will could use either cellulose or fiberglass. Cellulose will probably be a bit cheaper. If you are going to use rolls or batts, I would go with fiberglass.
user1007 is offline   Reply With Quote
Old 11-13-2011, 08:41 PM   #5
Don't WANNA do it myself
 
mnp13's Avatar
 
Join Date: Jan 2007
Location: Rochester, NY Area
Posts: 626
Rewards Points: 0
Default

Plaster and lathe construction


If I blow in, I'm going cellulose. If I do bats it will be fiberglass. I'm leaning towards cellulose, from the stuff I've read here and then researched online, but I'm concerned about the weight due to the amount I will have to use to get above the height of the joists.
mnp13 is online now   Reply With Quote
Old 11-13-2011, 09:53 PM   #6
Too Short? Cut it Again!
 
Join Date: Sep 2009
Posts: 9,635
Rewards Points: 0
Default

Plaster and lathe construction


Quote:
Originally Posted by mnp13 View Post
If I blow in, I'm going cellulose. If I do bats it will be fiberglass. I'm leaning towards cellulose, from the stuff I've read here and then researched online, but I'm concerned about the weight due to the amount I will have to use to get above the height of the joists.
Go for the desired r-value. You do not necessarily have to fill all the way up to the top of the joists.

If you can afford it. Think about insulating between the rafters too. Makes a big difference.
user1007 is offline   Reply With Quote
Old 11-13-2011, 11:21 PM   #7
Registered User
 
Join Date: Mar 2009
Posts: 9,968
Rewards Points: 0
Default

Plaster and lathe construction


Give us the span/size of the ceiling joists as plaster and lath weighs 8# per square foot: http://publicecodes.citation.com/ico...002_par023.htm

Plus the cellulose…


Plaster and a wood/metal lathe, like in school shop weighs 150-1500#.....

Gary
__________________
If any ads are present in my answer above, I do not condone/support/use the product or services listed, they are there against my permission.
Gary in WA is offline   Reply With Quote
Old 11-14-2011, 06:23 AM   #8
Don't WANNA do it myself
 
mnp13's Avatar
 
Join Date: Jan 2007
Location: Rochester, NY Area
Posts: 626
Rewards Points: 0
Default

Plaster and lathe construction


Sadly I don't own a lathe. And if I did I wouldn't keep it in my attic. lol (I have a captive spelling bee)

My joists are 2x12's. 1400 square feet, with one taller section where the ceiling is 11.5 instead of 9.5 like the rest of the upstairs.

I have telled a lie!!

Over one bedroom and two closets, the rafters are the joists - 2x12, 16 on center. About 18 x 16 of the attic. The remaining attic is 2x4, 16 on center.

I've been working mostly in the tall part. And it all blurs together.
__________________
Michelle

Fixing the re-muddling one room at a time...

Last edited by mnp13; 11-14-2011 at 08:09 AM.
mnp13 is online now   Reply With Quote
Old 11-15-2011, 08:50 PM   #9
Registered User
 
Join Date: Mar 2009
Posts: 9,968
Rewards Points: 0
Default

Plaster and lathe construction


I was trying to fogure your weight with undersized ceiling joists= 2x4's. Compare the span (distance between bearing walls) for the size joists with plaster at 8#- some charts here: http://publicecodes.citation.com/ico...002_par023.htm

And here: http://www.awc.org/calculators/span/...orizontal+Span

Then you have a better idea of how much weight in insulation can safely be added.

Gary
__________________
If any ads are present in my answer above, I do not condone/support/use the product or services listed, they are there against my permission.
Gary in WA is offline   Reply With Quote
Old 11-16-2011, 08:49 PM   #10
Don't WANNA do it myself
 
mnp13's Avatar
 
Join Date: Jan 2007
Location: Rochester, NY Area
Posts: 626
Rewards Points: 0
Default

Plaster and lathe construction


I have no idea what kind of wood it is. The house is about 130 years old, western NY. I do know it's like drilling through cement though, it dulls bits like crazy and my 18v battery drill is useless for anything other than one inch screws I have a corded drill for any holes.
__________________
Michelle

Fixing the re-muddling one room at a time...
mnp13 is online now   Reply With Quote
Old 11-19-2011, 11:23 PM   #11
Don't WANNA do it myself
 
mnp13's Avatar
 
Join Date: Jan 2007
Location: Rochester, NY Area
Posts: 626
Rewards Points: 0
Default

Plaster and lathe construction


Turns out the size of the joists depends on the area of the house. The ceiling of our bedroom is higher than the rest of the upstairs and hits the rafters, so those are 2x12. The ones in the rooms across the hall from the high ceiling area are 2x4. The ones at the other end of the house are 2x6. Weird.
__________________
Michelle

Fixing the re-muddling one room at a time...
mnp13 is online now   Reply With Quote
Old 11-20-2011, 02:04 AM   #12
Member
 
Join Date: Sep 2011
Posts: 166
Rewards Points: 0
Default

Plaster and lathe construction


The weight of fibreglass per sq ft is less than a 200 gm bar of chocolate, so this is the least concern. Go for 4'' good quality fibreglass batts, (avoid the cheap Chinese crap) tightly fitted between joists. Good quality batts are denser than el cheapo's because I think they tease a 3'' batt to 4''. Believe me, I bought a house lot of both, the difference is startling and I ended up dumping the Chinese version. Don't push the batts hard against the lathe, leave an inch or two. This actually gives you 20% free insulation because of the trapped air pocket between the ceiling and the batts. If the batts are too skinny and fall between the joists, lift up each side and staple edges of batts to joists either side. Always cut the batts 1'' wider than the space between the joists, then you can gently push down on the edges to the desired height and you don't need staples.

That's really all there is to it. Once you get the hang of it, you should do the lot in less than 8 hours. Because you can't step beween the joists, your knees will get a massive workout, so wear knee pads. Also don a throw away thin plastic rain coat-body suit or the ones painters use and cover your head and face as much as possible. Wear a good quality face mask, gloves filter over your nose & mouth, or a breathing mask. A proper gas mask would be ideal. If you haven't experienced fibreglass on on your skin, your going to experience some hell, so cover up. The science has been unusually quiet whether glass fibre can do the sort of damage asbestos fibre does to your lungs, and until they prove otherwise, I wouldn't take any chances. By the way the good quality batts are far less prone to shed fibres.

Cheers from Oz.
JoJo-Arch is offline   Reply With Quote
Old 11-22-2011, 11:34 PM   #13
Registered User
 
Join Date: Mar 2009
Posts: 9,968
Rewards Points: 0
Default

Plaster and lathe construction


JJ-A, in regard to the 20% R-value for a 2" air space, my understanding is that a void up to 4" deep only gives you R-1 total: http://www.coloradoenergy.org/procor...f/r-values.htm Bottom of charts, though they don't say if that is a vertical or horizontal void, as in the air films of walls/ceilings, just above. I think it would be the same, or am I wrong?

The insulation should be tight to the drywall/plasterboard for full contact according to this, fig.2 and 3: http://www.aecb.net/PDFs/Impact_of_thermal_bypass.pdf Your thoughts?
I do agree with the f.g. danger, open a roll in front of a strong light (take a picture and see the fibers floating like snow--- cool) or look in the bottom of the plastic bag after removing......

Gary
__________________
If any ads are present in my answer above, I do not condone/support/use the product or services listed, they are there against my permission.
Gary in WA is offline   Reply With Quote
Old 11-23-2011, 04:08 AM   #14
Member
 
Join Date: Sep 2011
Posts: 166
Rewards Points: 0
Default

Plaster and lathe construction


Gary, there is nothing inside fibre glass batts except fibres and trapped air. It's the trapped air that provides the insulation. Firstly the amount of convection (air movement is almost zero) the amount of radiation is low because of the density of the fibre and conduction is practically zero as glass is one of the worst heat conductors known.. So fibreglass takes care of all three methods by which heat can transfer. Convection, conduction and radiation.

By trapping an 1'' of air between the ceiling and the bottom of the batts, is like putting in 5'' of insulation, 1'' of air and 4'' of fibreglass. The air void by itself is not as efficient as an additional 1'' of fibreglass, because without the fibres, air can move and transfer heat by convection and some radiation, so 20% extra benefit is I admit, a little optimistic, and perhaps 10-15% more realistic, but there is a definite benefit not to place insulation hard against the ceiling.

Cheers! from Oz
JoJo-Arch is offline   Reply With Quote
Old 11-24-2011, 09:27 PM   #15
Registered User
 
Join Date: Mar 2009
Posts: 9,968
Rewards Points: 0
Default

Plaster and lathe construction


Any gap will promote air movement: http://oikos.com/library/insulating_...lls/index.html

The “water-wheel” effect of leaving a void letting the heated air rise being replaced with cooler air: http://findarticles.com/p/articles/m...6/ai_n8582994/

“Floor insulation also directly impedes conduction and radiation to the colder air below the floor.” -----http://oikos.com/esb/38/floorinsulation.html
So if you leave a 2” gap, wouldn’t the heated air from below easily travel through being only R-1? If it was tight to the ceiling, the full contact would slow the heat transfer because of more individually trapped air pockets available closer to the heat source. Especially if a wiring/plumbing hole was ineffectively plugged, the incoming air could travel the joist length or width of the whole house, rather than be limited to the immediate area by insulation. The gap would also give a “head-start” to encouraging convective loops if the f.g. was low density, which many owners pick because of lower cost.


Insulation reduces heat flow. Consider an R-15 batt is R-4.29 per inch compared to R-1 (air gap) per up to 4 inch. It is 4-1/4 times more effective at slowing heat loss. In addition, you would be heating the joists sides (4” total) rather than slowing the heat, which are R-1.25 per inch. So now the joists are bigger thermal sinks, speeding up the heat loss at R-7 instead of only the bottoms at R-1.5” surface area. http://www.greenbuildingadvisor.com/...ort/html/12484

“Don’t be fooled by so-called dead air spaces. Small air voids slow heat flow,
but large voids don’t. A dead air space is one in which air does not move —
once a gap gets larger than 3/4 inch, convection kicks in and overrides the
insulating effect. Even though they contain air, uninsulated framing cavities
have little or no R-value.
Making contact. That understanding should govern the way batts are
installed in the field. They should make good contact with wall and ceiling
and nestle snugly against the subfloor within floor cavities. If the batts
don’t touch the inside face of the drywall or subfloor, convection coupled
with air leakage will seriously undermine their thermal performance.”http://www.advancedinsulationinc.com...Insulation.pdf

All insulation manufacturers’ installation instructions require full contact to get closer to the lab-rated R-value. Their value is determined at testing with full coverage on all six sides, anything less is a reduction in R-value. I just don’t see any value for a gap between insulation and the air barrier.

I fully understand the concept of insulation, just not the benefits of leaving a 2" gap. I thought maybe I was missing something brand new. Thanks for taking time to explain your reasoning to me.

Gary

__________________
If any ads are present in my answer above, I do not condone/support/use the product or services listed, they are there against my permission.
Gary in WA is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Tiling an outside wall over lathe and plaster and window mkjeld Building & Construction 8 10-28-2010 06:48 AM
cutting plaster and lathe that eats blades Mike in Arkansas Electrical 8 01-01-2010 10:13 AM
Stud Finding on Plaster and Lathe? Scotsman General DIY Discussions 9 12-06-2009 04:11 AM
Plaster and Lathe walls- covering with drywall Jrr1099 Building & Construction 4 03-24-2008 02:20 PM
Plaster walls and Lathe Keith in Connecticut Remodeling 5 01-03-2008 07:36 PM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.