Archives for June 2013

Factory-Built Modular Homes

Modular homes are an approach to modern construction that has slowly been gaining acceptance. Probably because the efficiencies of constructing buildings in a factory setting has several advantages. Regardless of the weather, the materials and crew are protected indoors; water damage is eliminated and productivity is high. On-site time is greatly reduced and much of the construction waste is handled at the factory.

I recently went on a tour of Guildcrest Homes in Morewood, Ontario, just outside of Ottawa. Several model homes are on display at the property to help purchasers see some of the many designs available, but the real action is in the factory behind. In a one hundred thousand square foot building, house modules start their life at one end of the building and emerge at the other end packaged and ready to ship. The company manages the construction process through eighteen stages of completion supplying materials and related tradespeople as required.

First wall on deck In the first stage, the deck is built and set onto steel wheels that guide the developing module through the factory on tracks in the floor. Here we can see that a protective layer of paper has been laid down on the deck and the first wall section has been lifted into position by crane. The section already has vapour -barrier and drywall installed. To the right, we can see a module that already has its interior and exterior wall sections in place.

Walls up The factory has workshops that specialize in producing various sub-components like stairs and roof trusses. The sub-components are made to the custom requirements of the individual module’s design and transported to the factory just in time for assembly. With the framing done and drywall in place, crews can work to install electrical and plumbing from the outside and the interior through openings in the drywall where required.

Siding and trim Insulation, sheathing, windows and doors, siding, soffit and facia trim are all applied on the exterior while drywall is taped sanded and painted on the inside. The completed module will have shingles and interior finishes including flooring, cabinets and plumbing fixtures installed. Sufficient wiring is bundled at the end of each electrical circuit to complete the run to the electrical panel. I’ve glossed over the work performed here pretty quickly because the materials are not unique its the environment and the order they are installed in that differs.

In normal construction emphasis is on getting the building envelope sealed so that materials are protected and the work then shifts to building from the outside shell inwards. In the factory environment, once the drywall is installed work can be performed on both sides of the wall. Supply of materials is much easier, as is working from a level concrete floor or from permanent overhead scaffolding when shingling the roof.

Ready to travel At the end of the production line, the module is wrapped in plastic to protect it from the wind and elements while shipping. Hydraulic jacks lift the module off the steel wheels and onto higher stands. A transport truck backs a trailer under the module and it is lowered to be hauled away. Guildcrest’s website has a nice sequence of shots showing the craning of the finished modules onto a waiting foundation. Their installation makes for a dramatic advancement in a single day at the construction site. Of course there is still work to be done on site to link the modules together, connect electrical and plumbing runs and install any brick veneer or stonework required.

Guildcrest estimates that only one percent of the new-build housing market is being supplied by factory-built modular homes. Given it’s advantages we are likely to see more of this approach to residential construction. As a home inspector, I like the potential of higher quality construction in homes that are better sealed from the elements. If significant cost savings are passed on to the consumer, expect to see more modular homes going up in a subdivision near you.


Author: Rob Cornish is a Home Inspector in Ottawa, Canada. © 2013 HomeXam Inc.
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Engineered Trusses

The traditional method of assembling the wood framing members that hold up a residential roof structure was a manual process of custom cutting rafters, ceiling joists and the various pieces required. For the last couple of decades, virtually all roof framing is built as factory manufactured components that are assembled on site. There are several advantages to this approach. Engineered designs allow greater loads to be carried with smaller dimension lumber; saving material costs. Greater uniformity in the components helps with the quality of construction. Factory automation provides labour savings on-site as trusses can be lifted into place as finished components. Less skill is required in the field and roof structures can be framed in less time.

Truss manufacturing companies serve builders by efficiently producing trusses at their factories and shipping them to the construction site. Smaller trusses are lifted by hand and larger ones are often lifted by crane to be installed. The process start with specialized design software that takes design parameters as input and creates truss designs that meet load, span and code requirements. In large part, trusses form a repetitious design element where each truss is offset parallel to the next by a standard amount.

A truss is made up of a top and bottom chord and supporting pieces between called webbing that are often arranged in a triangular pattern. There are truss designs to accommodate different requirements like cathedral ceilings, attic storage, tray ceilings and so on. Truss manufacturers cut several of each component and assemble the parts in jigs for speed and accuracy. At the joints, the pieces are held in place by a gusset, which is a plate with many fasteners. In earlier versions the gussets often were a piece of plywood covering the end of several parts held together with numerous nails. Now the most common gussets are galvanized sheet metal cut with many tangs that are pressed into the wood.

Laying out truss components

You can see how the workers assemble each part of the truss on a table according to the design. Gussets are laid on the joints and a press rolls into position and pushes the tangs down into the wood for a strong and secure joint. The process is repeated over and over until enough trusses have been produced for the house. Then they are shipped to the construction site. The first picture shows the layout of pieces and the second the press in action.

Pressing the gussets

In the example shown the trusses are relatively small and only form one half of the roof for a modular home. It’s not uncommon for trusses to span more than thirty feet in length and take the entire load for that distance. This removes the need for load bearing walls in the interior space of the house and facilitates open designs and subsequent interior renovations. Because trusses carry so much of the load in a house, it is critical that the design follows engineered specifications and that the plan is followed accurately on site. Municipal building officials help to ensure that code issues like nailing, bracing and other requirements are consistently applied. As home inspectors, we visually examine the trusses, typically from an attic hatch, to see if we can spot any damage to truss components or improper modifications. Given the limited view possible from this vantage point it can only be a cursory examination.


Author: Rob Cornish is a Home Inspector in Ottawa, Canada. © 2013 HomeXam Inc.
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Knob and Tube Wiring

Knob and Tube wiring was one of the earliest techniques used to distribute electricity in our homes. It’s referred to as Knob and Tube because of the ceramic insulators that were used to pass the wire through and around obstacles. The Tube lined a hole through a stud or joist and the wire fed through it to protect the structure from contact. Knobs were used to secure the wire and at points with changes in direction. The wire itself was a product of the times; copper with a cloth woven covering impregnated with a waxy substance to protect the wires from moisture. Unlike modern wiring, each conductor was a separate wire and there was no ground wire.

Aluminum wires in electrical panel

The first installations were all retrofits and the wiring was mounted on wall surfaces. As new homes were built knob and tube wiring was incorporated into the wall structure like today’s wiring is. Since using electricity was new, there were very limited uses for it and the amount of current supplied was small, typically 30 amps. Today’s homes use at least 100 amps and in those of any size 200 amps is common. As new electric appliances, televisions, computers and other devices came along electrical services were upgraded in older houses.

It wasn’t overly difficult to upgrade the electrical service and distribution panel, but the existing distribution wiring hidden in the walls was a greater challenge. The effort and disruption of opening walls to replace the wiring was more than many homeowners were prepared to undergo. Often older houses developed into hybrid systems. This left sections of Knob and Tube wiring in some of the more difficult to access original sections of the home and updated wiring was used in remodelled sections and new additions.

This is part of the reality that home buyers face today when purchasing homes that predate about 1940. Somewhere in that building one or many runs of old Knob and Tube wire may still be hidden in the wall. It’s not that the wiring doesn’t work, but it doesn’t meet modern electrical and safety standards. Amateur connections between old and new wiring can be problematic and because the presence of Knob and Tube is considered undesirable, old wiring is sometimes left hidden and goes undisclosed. To be fair, the current owner may have no idea that it’s there.

Ultimately this falls into the risk that a home buyer accepts when they purchase an older home. Along with the charm comes the workmanship and technology of the day. As Home Inspectors, we look for signs of Knob and Tube wiring, but it’s a visual inspection and we can’t open up the walls to satisfy our curiosity. Another reason that Knob and Tube wiring becomes relevant at the time of purchase is that insurance companies are none too fond of it. You may have fewer companies to choose from, and those that do cover it, may do so at a higher cost.

The purpose of this article was to help you understand Knob and Tube wiring and the issues it raises in buying older homes. Wiring issues can be always be addressed with enough effort. It is just one of many issues to be considered and a licenced electrical contractor should be consulted when it is discovered. Hopefully the remaining use of Knob and Tube is limited and the associated costs to upgrade will be manageable.


Author: Rob Cornish is a Home Inspector in Ottawa, Canada. © 2013 HomeXam Inc.
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Aluminum Wiring in Houses

First of all, aluminum is a good conductor. It weighs less and costs less than copper. That’s why utility companies have been using it in their transmission lines for many decades and continue to do so to this day. From the mid-sixties to the late seventies aluminum wire was installed in residential electrical systems because the price of copper had spiked. You may have heard that the presence of aluminum wiring in a house is a cause for concern. I’ll try to explain what the issues are and you can decide what to do from there.

The primary concern is the risk of fire from improper installation. It all happens at the connection points. Aluminum oxidizes when exposed to the air. This really doesn’t matter except at the connection points between wires. Unfortunately aluminum oxide is a poor conductor. It creates resistance in the flow of electrons and it results in heat being generated. If there’s enough heat, there’s a chance of fire.

To add to the problem, aluminum has a different expansion ratio than other metals commonly used in electrical systems. Repeated heating and cooling of connections where aluminum wire joins copper wire or another metal, such as under a receptacle screw terminal, can cause the connection to work its way loose. Once loose, oxidation between the formerly airtight connection now starts to build up.

There are products that have been developed to help deal with these issues. One is anti-oxidant compound that can be applied over the tightly twisted ends of the wires. It looks and feels like grease and blocks oxygen out of the joint to stop oxidation. Special aluminum-rated connectors or “Marrettes” should be used to join aluminum wires and aluminum to copper wires.

Terminal crews on components like receptacles and switches were improved to have more secure terminal screws. Of course these more specialized components come a significantly higher cost. To reduce cost, tradesmen have adopted the practice of “pig-tailing” the final connection. This means that regular components are used with a short “pig-tails” of copper wire which is then properly joined to the longer run of aluminum wire through the walls.

Aluminum wires in electrical panel

So if all this works, why do you still care about whether there’s aluminum wire in the house? One reason is that just the stigma alone may discourage buyers when you go to resell. On the other hand, if it doesn’t bother you there’s likely other buyers who don’t care either. There’s thousands of houses out there that are still happily standing with aluminum wire in them. Depending where you live another challenge might be getting insurance coverage. You are likely to pay a premium price when you find it.

So why don’t you just replace all the wiring with copper? The key question is how much it will cost. The major hassle is accessing those wires behind the walls. Bungalows with unfinished basements are the easiest to deal with since the electrician can get to most of the wiring directly. When you have to open up the walls and repair them things quickly get more challenging and expensive.

Hopefully this article has given you a better understanding of why Home Inspectors try to point out the presence of aluminum wiring in any house they inspect. You should have gained an idea of the impact that its presence may have on you. For some it’s and major issue and for others it’s barely a blip in the new home buying process.


Author: Rob Cornish is a Home Inspector in Ottawa, Canada. © 2013 HomeXam Inc.
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