Wednesday, January 25, 2012

Cap and Boots (II)

In the previous post in this thread I dealt with two of the most vital components in terms of keeping a house protected from the elements over time: the roof (cap) and the foundation (boots). You can have the fanciest German triple glazed low-e windows, doorbells with fancy chimes, Brazilian Cherry flooring, and gold-plated faucets, but if the foundation or roof have been shoddily built, all the trimmings amount to little more than lipstick on a pig. The trouble is, the way we build houses, the foundation and roof are two of the parts of a house which are often the most concealed from view. Out of sight means out of mind and the cap and boots tend to receive little to no attention until a problem arises.

Couple this hidden world with a culture that is programmed to be obsessed with superficial concerns, and you end up with some confused priorities. A couple gets a full reno done on their kitchen, gleaming new stainless jacketed appliances which will fail probably in 15 years, particle-board biscuit-joined cabinets with some jazzy veneers that are just making their 10 year detour before the landfill, and some clever accent lighting and tile work. They have guests over who ooh and ahh over the new kitchen, and they feel pride in 'what they have built'. But if the same couple instead put a new roof on or repaired the foundation, they're unlikely to receive the same accolades from their guests - I mean, how does one show off a new roof exactly? "Hey, look at the freshly-pointed bricks" is at best going to elicit an uncomprehending stare, a facile oh that's great!, or a quizzical look perhaps - why are you telling me this? The things that are most important in terms of the integrity of the house we tend to pay little attention to - and I mean that in respect to all phases of the life of the house, from the initial siting of the building without respect to where the sun shines, to its ever-so quick construction, to the places where we spend money on the house, to the areas which are given maintenance.

A constructional system in which critical aspects are concealed from view turns out to be a problem affecting many other aspects of the buildings we inhabit. In this post and the ones to follow I wanted to look as some of the less obvious aspects of a building, particularly old buildings, many of which I have had a good chance to examine over the past few months. First up: electrical.

Wiring.

Wiring needs to be protected from impacts and tends to look unsightly when visible, so we hide these systems in the walls and floors. The problem is, if there are problems with these systems later on, they are difficult to work on without, in some cases, ripping the walls and ceilings out to gain access. If the wall is sheet-rocked, this is not such a traumatic event, however most older houses have lath and plaster walls, not to mention one or more layers of wall-paper, cast plaster moldings, etc., and thus the decision to rip such walls out are not made lightly.

Many old houses around here have remnants of knob and tube (K&T) wiring:


In the photo you can see the 2-piece porcelain knobs fastened to the sides of the studs, and the tubes are the little ceramic pipes which guide the wires through any penetrations - like the wall plate in the above picture. This wiring is visible in old houses, particularly in the basement and attic. K&T wiring is/was quite safe when installed properly. The porcelain standoffs have a virtually unlimited lifespan, and even if the fabric jackets on the conductors is in poor condition the porcelain connectors keep any wire, even a bare one, safely insulated. The open air aspect of the design allows any heat in the wires to dissipate readily. Another advantage: by arranging wires on opposite sides of building structural members, some protection was afforded against short-circuits that can be caused by driving a nail into both conductors simultaneously.

It's a safe system in certain respects, but after 80~100 years, well, not so much. Two main weaknesses of this system are the lack of a ground conductor and a switch-protected neutral which could turn off a circuit (but not, unfortunately, the current).

The reason that K&T wiring was employed in early electrified structures was that it was, surprise-surprise, the cheapest option. According to one book, Wiring Houses for the Electric Light (1916), flexible armored cable cost about twice K&T, and conduit cost about three times the of K&T.  Knob and tube wiring persisted since it allowed owners to wire a building for electricity at the lowest cost. Not much has changed I guess. The alternatives were armored cable (commonly termed 'BX' cable), and using conduit.  In the aforementioned book, page 84, the matter is spelled out clearly:


While this K&T system was adequate in its day, problems do arise over time, as the building learns, to borrow a term from Stewart Brand. One issue is that of subsequent splicing of new wires into old. With additional branches and fixtures added, fuses are likely to blow more frequently. Then what people will do is install larger fuses, an unsafe solution since the wire and fuses are meant to be related to one another in capacity. The wires in such a system then tend to overheat from the added loads, which causes their insulation to become hardened and eventually the insulation starts to disintegrate.

Some people do not grasp that these cloth covered wires in their basement actually carry electricity, and may do unwise things, like hang their damp laundry off of the wires. Another problem that crops up with K&T wiring systems is that of retrofitting insulation in the hope of improving energy efficiency - this being installed quite often in attics where the K&T is also placed. Fitting insulation in and around the conductors of a K&T thwarts their ability to dissipate heat, and thus a potential fire hazard is created. Of course, this practice is now forbidden in building codes, but not every householder chooses to employ contractors who adhere or are aware of provisions of the building code.

Certain rodents seem to like to chew on the conductors - probably they like the fabric. Basically, houses with the old K&T system still installed are living on borrowed time. Many insurance companies will not provide insurance unless all the K&T is removed, and tearing it all out can be costly. Some older houses have had parts of the old wiring ripped out, but if the job was not done thoroughly and carefully, there still could be remnants of the system in place which are live. Then you have a mystery wiring situation on your hands, where it can be hard to tell what is part of what.  I've run into this problem doing renovation work before - an old wire is thought dead, the breaker switched off at the panel and then you go to cut that wire and zzzzzzzzz!  Not recommended!

The system which supplanted K&T after about 1930 in most N. American households was one based on encasing two or more conductors (but no ground wire) in a polymer sheath. This system is present in most houses built before the mid 1960's. If the receptacles in the wall only allow for two-prong plugs in your house, then you have this system. Since the early 1960s, wiring in new construction has required a separate grounding conductor used to bond (electrically connect) all normally non-current carrying parts of an electrical installation. To bring an older non-grounded electrical system into line with modern practice is costly and may require walls to be ripped open, so a lot of old houses have not had their wiring upgraded. The very way in which the wiring is placed in the walls, passing through studs and stapled into position, makes it a hassle to repair or replace. It's not an integrated part of the building system really.

In my current rented accommodation, only two receptacles in the apartment accept three prong grounded plugs, and this is inconvenient to say the least. My computer, for instance, is plugged into a surge protector, but the surge protector in turn has to attach to an adapter so that it can connect to the two prong receptacle. I can fasten a small screw to the adapter which connects it to the receptacle, but have no idea if the receptacle is properly grounded. So I live in hope of not having to have this system tested by a voltage spike.

I agree with that 1916 wiring book - the best way to wire a house is to put the wiring inside of conduit. It costs more to do so, maybe, but it allows wires to be pulled in and out with relative ease, which makes the system more resilient and adaptable over time. It's a question, I suppose, of having foresight so as to devise a system with problem-prevention in mind, which is relatively cheap in the long run, versus a system which might be cheapest to build initially but has no allowance for anything but problem-cure, which is often expensive. If the wiring isn't easily repaired and adapted to new circumstance, then the wiring tends to become a drag on development and in many cases a trade-off happens between the cost of making changes weighed against the risk of having electrical problems down the, uh, line.

In the next post I'll get the lead out with a look at plumbing. Thanks for visiting the Carpentry Way.  ➦ on to post 3

8 comments:

  1. Surge protector is useless without a good ground. Get cheapie outlet analyzer from hardware store and find out for sure.

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  2. R. Davis,

    good idea! It would be something to add to my 'to-do' list, except for the fact that regardless of what I found out in regards to the outlet's grounding, my landlord would do nothing about it. So, there's no point.

    ~Chris

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  3. Chris,
    Kudos on your excellent survey of residential wiring. I just finished the rough-in wiring of my own home using metallic wireways ie, conduit, flex, and mc cable last week. It cost about thirty percent more in materials and took three times as long as installing a non-metallic system but I wouldn't have it any other way. In my opinion, having been in the electrical trade for twenty five years now, residential wiring as commonly done with NM-B and plastic boxes represents everthing that's wrong with modern homebuilding. In fact I'd go so far as to say that it's unconscionable. If a wiring sytem leaves even a hundreth of a percent chance that it will lead to fire or electrocution then there is no place for it. When I was in the residential phase of my apprenticeship a master electrician who was loath to Romex taught me to quickly unroll wire in such a way that every inch passes through my thumb and index finger in order to detect damage. I estimate that one roll out of a dozen has damage that necessitates it being cut out. It could be a manufacturing defect, the roll could have been dropped on the ground and it's outer and inner insultion pierced,
    you name it. Sadly, most electricians aren't on the look out for things like this, nor are they wiring with the care and consideration that future occupants deserve. Sorry for the rant when I just wanted to thank you for the post.
    Michael

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  4. Michael,

    you're more than welcome to 'rant' anytime - I enjoyed the read and appreciate your perspectve!

    ~C

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  5. Chris,
    As with so many many of your posts here, I am enjoying this so far and look forward to reading more. I have been working with a few different carpenters over the last few years, and have had the chance to poke around inside quite a few old homes (and not so old), seeing what they did wrong or could have done better. All of this time I have plans in my mind for my future dream home that I would like to build. Every time I see something shoddy or hard to access for repair, I revise the plans. I haven't done much if anything with electrical, so hadn't given any real thought to it, but this post makes too much sense. By the end, my house is going to be awfully strange, but at least it will be comfortable and easy to care for.

    I have worked on a number of ice-dammed roofs this past year as a result of last winter, and according to everything that I've read (and simple applied physics), the best solution for ice dams is to properly insulate and seal the attic to prevent heat leakage through the roof plane. So far the only roof dam repairs I have done include tearing off part or all of the roof shingles, replacing rotten plywood along the eaves, and laying down a rubber roof membrane such as Grace Ice and Water. No one is willing to go through the process of really fixing the issues, they just want to put a bandaid on it.

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  6. Simon, yep, you've got that right. A nation of bandaids and quick fixes I'm afraid, and a lot of money and energy wasted. Thanks for sharing your perspective.

    ~Chris

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  7. "an old wire is thought dead, the breaker switched off at the panel and then you go to cut that wire and zzzzzzzzz! Not recommended!"

    That how I got tiny holes in the cutting edge of my side cuts...more of a POP!sound... NotCool!

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  8. I guess that would be the joy of insulated handles...

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