Tag Archives: technical

Understanding Historic Masonry

I have no first-hand experience when it comes to masonry but I know the advice to give: “Repoint masonry with the correct mortar mixture!” “Test and match the historic mortar!” and “Don’t use Portland cement!” (which, Mr. Chimney-repair-person, is NOT a brand, but only the most common type of cement used in mixes).

While it might look nice at first, the wrong type of mortar can cause much worse deterioration of the masonry and/or structure, I know that, I’ve seen the evidence and been convinced; but when it comes to repointing deteriorating mortar in stone or brick what is really the deal? I mean, how likely is it that all the historic mortar that needs repairing will be mixed like in the olden days? What materials are practical and reasonable for masonry repairs in 2016? What can we expect/demand from our mason, and what is critical?

There is a house in metro Atlanta that dates to the 1840s and its 2 chimneys are built of field stone (mostly gneiss) held together with a lime-based (soft) mortar. But carpenter bees are making homes in the mortar and snakes are finding their way in through the gaps. Patches of the intervening years are insufficient, unsightly and may be causing more damage, it’s time for a thorough overhaul, knocking out the loose mortar and repointing the entire chimney.

I found I didn’t really know what to advise beyond the rhetoric, so I put in a few calls and went waaaaayyy down the stone-lined rabbithole. I came back with something of a better education and a collection of good reads that I’d like to pass on.

Simply Put:
Besides the obvious needs of making a watertight and structurally sound wall, your primary concern should be the softness of the mortar in relation to the brick or stone. Mortar should ALWAYS be softer than the masonry units so that water vapor, particularly from the inside will pass through the mortar as it dries out. If the mortar is harder (less absorptive) than the individual masonry units, water will be forced into the brick or stone causing them to expand and spall. The appropriate mortar will flex with the changes in climate and settling of materials. This is especially important with soft historic brick (pre-1890)

How bricks and mortar work, and don’t. Illustration from Old House Journal.

A Brick and Mortar History:
This “Short Course on Historic Mortar” from Old House Journal tells it best:

Until the mid-19th century, bricks were produced by hand-packing molds sprinkled with sand or water, depending on the desired finish. When combined with small-scale firing, where bricks at the rear of the kiln often received insufficient heat to initiate the sintering process, this process tended to produce bricks that were quite soft. By the late 19th century, however, extruded, wire-cut bricks were replacing even the machine-packed and kiln-fired brick that dominated mid-19th-century construction. To be safe, it is reasonable to assume that if your house was constructed after 1890, it is very likely to have been built with relatively hard brick. If construction was completed before the 1860s, the brick is very likely a soft brick. Paralleling this period of brick production was the availability of hard Portland cement. First produced in the Lehigh Valley of Pennsylvania in 1871, Portland cement quickly began to supplement and later supplant lime mortars. From about 1880 to World War II, mortars were likely to contain both lime and Portland cement. By the second half of the 20th century, most bagged masonry cements contained Portland cement and sand with little or no lime.

The contractor (John Wesley Hammer) working on the Peters Mansion in Atlanta, “used lime, a small amount of portland and aggregate dug up on site consisting of clay, mica, sand.” This aggregate mix helped match the historic mortar in color and texture which was necessary for the small joints in this Victorian home.

Stone is a different story. First you need to determine what type of Stone you’re working with, granite, found a lot in Atlanta, is one of the hardest stones, a rock of the igneous family, and generally is fine with hard mortars. In my research I found that Type N mortar mix, which was used on Rhodes Hall recently, is probably a reasonable bet, read up on mortar mixes at US Heritage Group. Field stones are very common and can be a mix of stone, though, in North Georgia this still involves a lot of granite and gneiss (also pretty hard). Identify your rocks here: Building Stones

previous patching

previous patching

deteriorating mortar joints

deteriorating mortar joints

Final Notes:
For starters, mortar joint deterioration is not the end of the world, like a house needs new paint, mortar joints will eventually deteriorate (though a good job could last 50-100 years), ideally the mortar deteriorates before the bricks or stone do!

It would be most helpful if you found a contractor with an understanding of historic masonry, however, after some good research (see below) and what you know of your building’s history, you should be in a good position to discuss the most appropriate formulation.

and: “Don’t be afraid to insist on a softer mortar.”

RESOURCES:
“Short Course on Historic Mortar” from Old House Journal.
– Preservation Brief 2: Repointing Mortar Joints in Historic Brick Buildings
Mortar Mixes: A Quick Primer from Eldorado Stone

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the Great Window Debate

Since M started the blasphemous discussion of tear-downs and window replacement in my house the other night I have been lying awake thinking about it. I can see that double-paned glass is more energy efficient than single-paned, I know you can feel the difference. I know energy efficiency is environmentally friendly, in fact I hope that environmental friendliness will save the world, but I also know the enormous environmental costs of demo and new materials, that any salesman will inflate energy loss/efficiency numbers to their advantage, and I have seen how very restorable older windows are vs. the short life span of replacement windows.

I know Preservationists’ biggest argument is often about “the historic character” of something but we have to acknowledge that many people just don’t give a damn, and that’s, well, that’s fine.

While preservationists protested, a few other people were doing their homework and refuting window replacement with valid arguments. The following articles cite findings that the time it would actually take to save $$ on this big investment (replacement windows) was consistently around 30 years, more than twice as long as the time it would take to recoup the investment in repairing and restoring existing windows. Read these (non-pres) articles on the pros and cons:
The Great Window Debate
Update Historic Windows

Energy efficiency, the environment and historic preservation are all important to me, and in my world they go hand in hand. In light of that, I’ve done my best here to be a good journalist. I’ve been honing my argument and this time I won’t even mention the aesthetic appeal:

  • Yes, double-pane glass is more efficient—it was a pretty great invention in fact.
    • Before double-pane glass came around people used storm windows to achieve that insulating layer of air. Storm windows (I prefer exterior and operable for use with double-hung windows) are still a brilliant retrofit option.
    • double-pane glass has gases between it that help filter UV and provide insulation, unluckily these can and almost always will eventually leak, leaving you with permanent condensation in the middle – yuck!
  • New windows require less maintenance
    • But the material is significantly lesser quality and unless you pay for custom built, high-quality wooden windows (an option many homeowners do, one at a time, when an old window really DOES get beyond repair), you will be replacing those windows wholesale in 20-30 years. Oh nevermind, leave that to the next homeowner.
  • Exterior storm windows also offer protection from the elements.
Operable metal storm windows at our house have been in place, I'm guessing, since at least the early '90s and though the wood windows are in need of paint at this point, they are far from deteriorating despite having not been touched in at LEAST 25 years.

Operable metal storm windows at our house have been in place, I’m guessing, since at least the early ’90s and though the wood windows are in need of paint at this point, they are far from deteriorating despite having not been touched in at LEAST 25 years. This winter, the wind rattled the windows but a little piece of cardboard fixed that and the storms kept the drafts at bay.

  • Most of the heat loss in your home is through the ceiling and walls, followed by the floor, windows and doors. Percentages range from 25-42% energy loss through the ceiling, 24-35% lost through uninsulated walls and 5-15% through windows. Hence, replacing your windows might feel warmer at the window but make little difference in the room’s ability to retain warm or cool air if the ceiling, walls, and floor are not properly insulated.
  • Speaking of which, old wooden windows SHOULD NOT be drafty! if you are feeling a draft around your window, it’s not because it has single-pane glass, it’s because it’s not sealed well which is infinitely fixable! Panes may need re-glazing (the putty that holds the glass in from the exterior), weather-stripping updated and/or caulk may be needed around the frame where it fits into the wall. Weather-stripping is the easiest of DIY fixes.
  • The replacement window industry wants us to buy new windows (duh), they’ve concocted all sorts of statistics and claims to make it seem like a no brainer. But even though their best claims were exaggerated, the damage was done, much of the general public was convinced that replacement windows would solve all their problems, and also:
    • Driven by consumer demand, the Real Estate industry lapped it up and preached the replacement window gospel.
    • Contractors will probably encourage you to get new windows too whether they believe in them or not because it SO easy to demo the old and install new and less time-consuming than restoring old windows.
  • Additionally, sending all your old windows to the landfill in favor of all new material that will go to the landfill in another 20-30 years (because they can’t be restored thanks to the low quality) wins some major negative environmental points.

In short, replacing your old windows is not a pat answer to the problem of heating and cooling efficiency in homes, and it is certainly NOT the first thing you should do to improve efficiency. Although houses will be different, air leaks should be sealed (windows and doors as well as outlets, baseboards, can lights and other problem areas) and insulation added before anything else is done.

Industry jargon needs to be analyzed, whether it’s from a Realtor, the Window Industry, OR a Preservationist.

If I’m trying to improve my comfort and save $$, I would restore my wood windows hands down, seal drafts and make sure I have sufficient insulation in the attic and floor which will have a greater effect on the comfort level of the whole room. I might even install storm windows if I wanted to spend a little more money and really reap the efficiency benefits. If a window was so far gone it had to be replaced, I would certainly take advantage of double-paned glass, but get a good quality wood window custom built to match the others so that I wouldn’t need to replace all the windows in my house for aesthetic reasons.

What about metal window frames??
I don’t know much about restoring metal windows in mid-century homes, although it can be done. I do know the frame gets quite cold. So I’m not surprised that you’d feel a huge difference once the metal windows in a ranch house were replaced with new ones. In this instance replacement seems reasonable, though I’d still be sure to choose quality windows without plastic bits that break.


green trials: lighting

After yesterday, I feel like I should put in a positive word for this green rehab project at RH. saving energy through lighting.

According to internet sources, lighting can consume 20% of your total energy use, and incandescent bulbs convert only 10% of the energy used into light! the rest is emitted as heat which makes them both super inefficient and dangerous as well if left on (if you’re the worried type). Switching to CFLs or LEDs is an easy and significant change, but I’m preaching to choir here right? Here at RH we replaced every bulb in the building with LED lights, (except for the bulbs dotting the reception room ceiling, which are relatively little used, low wattage, and we were hard-pressed to find an appropriate-looking replacement).

DSCN0268
We even found decent LED “candle” bulbs!

note: these too are MOST efficient if you don’t turn them on though.


going green: climate control

To some, energy efficiency and older buildings do not go together, but here at Rhodes Hall we are trying to prove you wrong. We have teamed up with Southface (or they with us rather) to create guidelines and a point system for LEED-like certification of the energy efficient rehab of historic buildings. The starting point of that being the inherent greenness of reusing an existing building to begin with.

Demolishing one building to build new and “more energy efficient” is like flaunting your choice of compostable paper plates and then throwing them away. YOU’VE MISSED 3/4 OF THE POINT!!

So, RH is serving as a pilot project to this green-rehab initiative. As we make necessary repairs to our building this year we are also making energy efficient upgrades, the biggest issue of course being climate control in the building.

While RH was formerly heated fairly efficiently by radiators (gas boiler in basement), the AC in the summer was another matter. Window units chugged noisily in all the downstairs and 2nd floor rooms while on the 3rd floor a central HVAC system kept us mostly cool but also cooled the uninsulated attic through leaks in the ducts. After much research and debate on the part of the Southface and The Georgia Trust and more debate before approval by the Board, we installed a central HVAC system (heat inverter?) downstairs zoned so that C’s office and the kitchen can be blocked off and controlled separately from the rest of the main floor which is often not “in use.” This was ideal for the museum/events space of our building, the least visible system we could install, but there is nowhere for ducts to run on the 2nd floor so up there, where most of our offices are, we installed top of the line split system electric units which are minimally invasive (least damage to the building itself and most removable), very efficient, and don’t block windows.

The basement ceiling and the attic were insulated with spray foam which has made the attic remarkably temperate year-round.

So how is it all working out?

Well, this is still a big building with high ceilings (for hot air to rise) and opulently expansive single-paned windows. On the first floor, the central heating does an excellent job of warming the entire area*, but on the 2nd and, subsequently the 3rd floors where we put in our 9-5, we are sorely missing the radiators. Here’s what seems to be the problem:

  • the individual room units are operated on a room by room basis, meaning the entire floor (notably the center hall and large bedroom opening onto that) are rarely heated. These large spaces of cold air make it harder to heat up our offices and, even if we close the door, we must pass through these unconditioned spaces to get to the bathroom, the copier, or any other room.
  • speaking of the bathroom, they did not receive any climate control at all and, since the 1st and 2nd floor bathrooms open onto unoccupied (and thus unconditioned) rooms, they are even colder, not an ideal place to pull your pants down. We got space heaters which take the edge off but the heat unfortunately is also rising into that 12 foot ceiling space!
  • there is no heat from the 2nd floor to rise up and warm the 3rd floor as there once was, so that by midday it is colder upstairs than ever (if the central air up here was actually warming that might help but i can’t say that it is)
  • we won’t even go into the aesthetics of the things.

center upstairs hall electric split system hvac

We have miles to go before our work here is done. Work on the windows for instance—fixing drafts, adding storm windows—may help heat retention throughout the building but we still have to turn on the heat and I don’t expect to come to love these Mitsubishi split system units.

I say, if you’ve got radiators then by all means maintain them and if at all possible find a way to install central air on all levels for the summer months. save the split system hvac units for hotel rooms or other closed off and smaller spaces. Despite the selling points of the Mitsubishi units (they ARE quiet and good air conditioners and efficient) I’m not sure they were ideal for us here, then again, anything is efficient if you don’t turn it on.

honestly, this is how energy efficiency looks at RH these days

honestly, this is how energy efficiency looks at RH these days

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ARGUMENT UPDATE:
I just ran across something on ZONE CONTROL on the US Dept of Energy website that better says I was trying to say about heating the whole house vs. just the rooms you are sitting in and something in between.

They write that “one way to save energy.. is to retrofit systems to provide separate control for different areas of large homes (RH). Zone control is most effective when large areas of the home are not used often or are used on a different schedule than other parts of the home.”—At RH this would definitely be the main floor/event space, and possibly the central areas of the 2nd floor, although… “Zone control works best in homes designed to operate in different heating zones, with each zone insulated from the others. In homes not designed for zone control (RH), leaving one section at a lower temperature could cause comfort problems in adjacent rooms because they will lose heat to the cooler parts of the home (unconditioned spaces).”

It goes on to say that you can of course enforce zone control/”insulation” by closing doors which we reluctantly do at RH right now though it shuts us off from each other. However, social/work interaction aside this is also not an entirely effective solution as everyone’s office opens onto the cooler central space and thus there is a lot of opening and closing doors. It would probably be advantageous to heat the central spaces daily in conjunction with our offices, thus providing a more reasonable level of comfort all around. let’s put these energy efficient units to work! sigh.

—-
* update in January: The HVAC system downstairs is failing miserable due to several likely factors: the basement now has NO heat where it was once quite toasty thanks to the boiler, this makes it harder for the heat inverter system to warm up and provide properly warm air to the 1st floor, it also means there is a major updraft from the basement door (we use the basement which is partially finished but unconditioned), even though, yes, there is insulation in the floor joists below the 1st floor.


how insulation works

I have recently rediscovered the “Preservation in Mississippi” blog and am trying to read it when i get a chance. This morning I delving into the concrete block construction fad in Vicksburg (this relates to studying for my test tomorrow i swear) and was curious as to why they claimed to provide excellent insulation. Some readers were curious too and one guy had an answer:

“The blocks used for the cap of the low wall show some playfulness with the block machine. The manufacture used a form for the short side of the block that was half the size of the block they were making. This gave it a half rockface, half smooth finish to the block.

“[The concrete block construction] claims are 100% valid. The continuous dead air space they refer to in the article is a pretty good insulator since dead air does not transfer temperatures. With modern insulation like fiberglass bats or spray foam (gasp, boo, hiss) its not the product insulating the structure but the dead air space the insulating material tries to create. Like Malvaney said air infiltrating the space will negate the value of a cavity.

“Well maintained this method of construction is fairly efficient. Although temperature transfer through walls is pretty low on the list of concerns. Walls are fourth on the list behind roof, floor, & openings(doors and windows).”

Dead air space provides insulation?! This was something I didn’t know but it makes sense of course. The “loft” of your sleeping bag or comforter keeps you warm (and when you loose that loft cause you washed it, you’re not warm anymore). I sought to verify this with a trip to howstuffworks and learned that the purpose of insulation is to retard the transfer of heat and since air is poor conductor of heat it is probably the most basic, effective, and accessible form of insulator. This would also explain [to me] why all these new thermal fabrics and such are so full of “technology” because they have to get around the most basic rules of insulation.


not exactly related, but this is a picture of the very uninsulated (and drafty) attic of Sunshine. You can imagine how all that hot hot air in the summer transfers DOWN into the house!