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House made with concrete block walls..??

bigbob2's picture

As the kids have moved out and NJ taxes are more than outrageous, the wife and I have put the house on the market and want to downsize.  We found an acre lot with a house and detached garage for my woodshop, not too far from where we now live.  The land is restricted to new construction due to the Highlands Act, but we can modify the existing home should we elect to buy it.  Here is my question:


I have built and remodeled plenty of wooden frame homes, but I have never worked on block wall construction, (other than to carry block all day when I was a rookie on a remodel crew!!).  One of my best acquaintances/friends who is an architect said that if the block was filled, it would have a great R-factor.  Would they build a house 60 years ago WITHOUT filling?  (I am asking the HO if the blocks are filled with... concrete?).  There is a 2nd floor that can be built out and that is why we are interested... that and the large piece of property.  It has been on the market for a long time... I imagine many are afraid of the block wall construction.  Should I be wary of this?  Or is this a great opportunity, all things else being equal?  Electric, wood roof, drainage, etc. all look good.  I'd like to hear from any masons, or builders who might have some opinion in this area!! Thanks.

(post #98692, reply #1 of 21)

Block is not bad, just different.  In your case, it's likely going to be like doing basement work, only with windows.


Are the blocks filled?


That's a hard call.  Likely, the jamb blocks are filled solid; the lintel courses are built solid--even odds on filled "U" lintel blocks or just concrete lintels back in 1945.


Check with the local electrical utility, some have a service where they'll come out and thermal video the house to see how insulated it is.  This might could tell you a lot about the house.


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(post #98692, reply #2 of 21)

Just out of curiosity, how would filled blocks have a great R value?  I thought masonry has a lousy R value - unless he meant filled with insulation in which case never mind.

(post #98692, reply #3 of 21)

Good Point!

Solid Concrete has a R-value of about 1/inch, IIRC. That's not terrible, but it isn't great either. Given its location, I would consider something like RayMoore's PERSIST system of insulating the whole lot 2" with XPS from the outside and putting stucco or whatever on top to get a R18 wall.

(post #98692, reply #4 of 21)

I, myself has built a concrete block house, filled 100% with concrete. Direct hit by hurricane Ivan with 0% damage. And looks like Dennis will hit it Monday. My highest power bill has been $29. it stays 78 degrees all year round. Brand new A/C that never been turn on.

On R factor, a better turn would be unit mass. Although the R factor is low. it heat up in day and cools off at night so they counteract each other. so the temp stays constant. it would not work in a very hot area or super cold area but with hot days and cool nights it works.

(post #98692, reply #8 of 21)

"On R factor, a better turn would be unit mass. Although the R factor is low. it heat up in day and cools off at night so they counteract each other. so the temp stays constant. it would not work in a very hot area or super cold area but with hot days and cool nights it works."

True. Solid concrete walls work best in warm climates though, where there are constant, wide temperature swings (i.e., Arizona). A concrete block house with filled concrete cores in New Jersey would probably get pretty cold in the winter.

I work in a building that used to be a repair garage in a gentrified area of Columbus, Ohio. We moved in a little over a year ago and have gone through a complete cycle of seasons now. The walls are 8" concrete block, and doubtful on whether there's any insulation in it. The space is great, but there's a price. Winter was freezing, and summer can be sweltering. Only an issue if its below 20 or above 90, but when it is you feel it. Of course we also have exposed steel bar joists 13'-0" from the slab on grade, with an exposed metal roof deck above. All the hot air goes straight up . . . still trying to figure out where the cold air is going. We sublease from the owner so they pay the electric bills, but they must be enormous.

I'd guess that New Jersey temperatures are pretty similar. If you don't have insulation you can look into a foam injection process. But your R-values will depend on on the density of the cmu (an 8" cmu with 60 lbs/cf can get R-14, with 140 lbs/cf the R-value is between 5 and 6 . . . which isn't much more than it would be without any insulation). Concrete block without insulation has an R-value between 2 and 4, by the way. Some knocks against core-filling is that it breaks down over time, so you might need to do some research. Otherwise, you might have to fur out with rigid insulation (or fur out some other way . . . namely getting some big dogs for those cold winter months). Good luck.

(post #98692, reply #9 of 21)

It's the constantly cold and hot temps of the Northeast climate that made me recommend putting the insulation on the outside, using RayMoore's construction technique. That way, the considerable thermal mass of the concrete walls helps buffer swings either way of the temperature scale.

A lot of thermal mass inside the home also opens up many other possibilities, such as taking advantage of demand metering (by only cooling late at night, for example). Then, the AC can stay off during the day, when the electrical demands peak and the electrical company is desperate to get load off the grid.

Retrofitting a 2" layer of XPS to the outside also shouldn't be too hard, though I imagine that careful consideration must be given to properly flashing extant penetrations (windows and all that).

I also agree that thick walls can be great in many climates where there is a fluctuation of temperatures and that concrete is the material of choice in hurricane-prone areas of the country. My mother was of the same mind when she built a home in FL, quickly dubbed "the bunker" by the local inspection department. Between the reinforced concrete, shatter-proof windows, and the Aluminum shutters, she should be OK.

Due to historic-district considerations, I could only fill the balloon-framed stud bays of my home with Corbond and Icyenene... but I couldn't be happier with the results. Naturally, you could insulate on the inside with XPS also, but that would negate the benefit of the thermal mass of the wall.

(post #98692, reply #5 of 21)

stucco has been put on outside, and I don't know what is on the interior.  Bills seem to be low, and they, too rarely run their AC.

(post #98692, reply #6 of 21)

We have a block construction house with terrazo floors.  Quite a bunker.  It is approx. 20 degrees cooler inside during hot, humid days, which I have always attributed to the floors not the walls, but maybe it is both.  We have done extensive renovations and of course needed significant sill and jamb extensions, and nailing strips for Hardiplank siding (even more cement) but otherwise the work seemed pretty straigtforward.  House hasn't sunk into the ground yet but it is heavy.

(post #98692, reply #7 of 21)

thank you, that corroborates the owners' story.

(post #98692, reply #13 of 21)

Sorry, the R-value of masonry is about One R per eight inches. Softwood is close to one/inch.

 

 


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(post #98692, reply #14 of 21)

Thanks for the correction. Block should be somewhat better than solid concrete in terms of R-value, but evidently, it's never going to be great. How would you approach this problem, insulate from the outside as I advocate or a different solution?

(post #98692, reply #19 of 21)

approach this problem, insulate from the outside


I've come to think of it as two-pronged situation.  You want the insualtion on the outside, for all the stated reasons.  But, you also need some sort of framed wall on the inside--because just not enough people like the look of all exposed mechanicals.


Somewhere in there, in the machinations that takes (furr out for eifs or persist; furrout for interior finish/mechanicals, too), treating it like an above-ground basement and earth-shelltering the walls gets to be right reasonable . . .


Now, expanding "up" from such a structure can be a dream, almost no hassles with is there enough structure, or how will we get good bearing.


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(post #98692, reply #21 of 21)

I like using faom outside and preserving the space and the thermal mass.

I suppose it could be done both sides. I have a cellar that is ARXX blocks - ICFs with over 2" of foam on each side. It is quiet and thermally efficient.

 

 


Welcome to the
Taunton University of
Knowledge FHB Campus at Breaktime.
 where ...
Excellence is its own reward!

 

 

Oh Well,

We did the best we could...

(post #98692, reply #10 of 21)

Not knowing your architect, I suspect he was suggesting core filled block is a fantastic "heat sink" which would work great behind a high R-value exterior finish, such as EFIS or stucco, to insure a very energy efficient home.


The block walls are a benifit if you are doing a second floor renovation/addition, especially if they are core filled. No worries about the load bearing capacity there. If the roof is stick built, you are effectively remodeling a wood framed structure over an above ground basement with CMU walls.


If you are altering the CMU walls however - Lord help you! It will cost at least twice as much if not more to renovate concrete walls than it will cost to renovate stick framed walls. If you are only planning an opening here or there, it's probably not going to be cost prohibitive. Just keep the modifications to the concrete to a minimum and it sounds like you've got a great opportunity.


Oh yea, be sure to check on possible height restrictions before you buy with plans to add on a second story too.


 


 


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If we fail to catch a cosmic fish it may be a trillion years before the opportunity comes again

(post #98692, reply #11 of 21)

Filling concrete block walls with insulation does essentially nothing to reduce heat transfer.  Most of the transfer occurs through the webs and not through the air in the core openings.


Concrete block has a lousy R-value, too, so you will spend a considerable amount heating such a building if you don't insulate, or if you insulate the cores only.


In your case you are better off insulating on the outside for two reasons.  First, having the thermal mass inside the insulation envelope tempers temperature fluctuations, so you will be more comfortable.  Second, concrete block is porous to rain.  Painting provides only spotty and unreliable protection against water soaking through the block.  If you insulate the inside you'll trap all leaked water within the wall which will lead to all sort of bad consequences.  It is better to insulate the outside, then side it with any normal siding material so the block never gets wet.

(post #98692, reply #12 of 21)

I'm with those who say that R-value is negligible, but if you can insulate the exterior, you can create a pretty good system with that thermal mass. Insulating the cores is next to worthless. I also agree with the guy who said it's most effective in its current state in areas with wide daily temp swings so that the thermal buffering has a chance to happen. Constant high temps, and especially constant low temps, will negate the effect of the mass. In a NJ winter, uninsulated mass will become and stay cold, and will make you feel cold yourself. I'd also keep an eye on interior humidity levels, be/c the block will not prevent moisture transfer.

I'd try to learn as much as possible about the structural parts, be/c there's a big diff be/t block only, and block with some rebar, and block with lots of rebar and all filled cells.

(post #98692, reply #15 of 21)

Local climate is a huge factor in the comfort of a block building.

I wouldn't do it in NJ without adding exterior insulation.

This is exactly the sort of application EIFS was developed for.

======================================== "Man's capacity for justice makes democracy possible, but man's inclination to injustice makes democracy necessary." Reinhold Niebuhr: 'The Children of Light and the Children of Darkness' http://rjw-progressive.blogspot.com/ ========================================

(post #98692, reply #16 of 21)

EIFS??? forgive me.... I don't know what this is.  It has stucco on it now.

(post #98692, reply #17 of 21)

Exterior Insulation and Finishing System - Exactly like stucco except different. :-)>

 


 


If we fail to catch a cosmic fish it may be a trillion years before the opportunity comes again

 

 

If we fail to catch a cosmic fish it may be a trillion years before the opportunity comes again

(post #98692, reply #18 of 21)

As Golden noted - aka "synthetic stucco."

It was developed in Europe for insulating masonry buildings./

It has a checkered history in the US having been poorly ionstalled on frame buildings: leaks can get trapped and cause significant rot and mildew problems in frame buildings.

Block buildings in the north can feel cold in winter because of the cooler wall surfaces.

======================================== "Man's capacity for justice makes democracy possible, but man's inclination to injustice makes democracy necessary." Reinhold Niebuhr: 'The Children of Light and the Children of Darkness' http://rjw-progressive.blogspot.com/ ========================================

(post #98692, reply #20 of 21)

EIFS??? forgive me.... I don't know what this is


It's stucco, or modified stucco (and occasonally synthetic stucco) applied over expanded foam sheets (which are supposed to be applied over an exterior sheathing like densheild with proper flashing & waterproofing).


The foam sheets allow the creation of complex shapes and masses without creating hard-to-support with light structure finishes.


Popeye's franchises are typically finished in EIFS, as are many modern strip centers.


Since it's portland plaster over foam, and the foam can be easily shaped, some very special effects are possible.  But, as with most things in life, you get what you pay for.


Occupational hazard of my occupation not being around (sorry Bubba)
I may not be able to help you Occupational hazard of my occupation not being around (sorry Bubba)