Moisture – The Un-seen Enemy In Your Home

Every week I receive calls from people asking for advice of information about wall movement, drywall cracks and humps in floors. Usually I try and answer these questions on the phone although some people are quite insistent that I visit their home to see for myself.

Most builders and contractors are professional and will take responsibility for their workmanship, others are quick to point the finger at somebody else, usually any other trade will do as long as it is not them. Tarion allows your house to settle for one year before they will look at or discuss any drywall cracking issues.

First problem is, your load of lumber used to build your home. Un-like myself when buying lumber, choosing the straight lumber takes up most of that time. On the other hand, your home package is dumped off in one large skid at the construction site. So your framer has just the right amount of lumber to build your home. Most framers won’t bother checking moisture content and straightness of the lumber, he will make do with what he has. A good framer will use most of the warped pieces as fillers etc where they won’t matter as much.

Most homes in the Barrie, Alliston, Orillia area have 2X8 floor joists. If it is raining when your package is delivered these joists will be exposed to extreme moisture until the roof is completed. This is a recipe for high moisture content and eventual shrinkage and possible warping etc.

As the lumber gives up this moisture, the change in size can be dramatic. But it is important to know that a standard piece of lumber does not shrink the same amount along all of its dimensions. The greatest amount of shrinkage occurs across the face of the grain.

Let us assume that a standard 2×4 that is 8 feet long will be exactly 96 inches long, 1.5 inches thick and 3.5 inches wide. Once this 2×4 has been in your house for 6 months and had a chance to acclimate and dry out if it was wet, it will still be nearly 96 inches long. There is very little shrinkage along the length of the lumber.

The thickness of the 2×4 will change slightly, but not by much. But the width of the 2×4 will experience the greatest shrinkage. It may only measure 3 and 3/8 inches in width. Imagine how much shrinkage might happen with a large 2 x 12

Wood shrinks only when moisture content falls below about 30%. A 6-in. wide treated southern pine deck board should shrink by about 3/16 in. if it reaches 12% EMC, so laying wet decking boards tightly against each other should result in a 3/16-in. gap when the boards dry (photo top right). For redwood or cedar purchased at 20% MC, a nominal 6-in. decking board will shrink only about 1/10 in. when a 12% EMC is reached. If the lumber installed is drier than the local EMC, and if the boards are laid tight, there’s potential for the wood to pick up moisture. swell and buckle.

Truss uplift is a condition where the bottom chord of a truss lifts or cambers in the winter and then lowers again in the spring. The movement of the truss is caused when there is a temperature and moisture difference between the top chord and the bottom chord. The wood in the top chord expands with the absorbed moisture from the attic space. The bottom chord remains stable with the heat from the space below. Structurally this is not a problem but it can produce cracks in the tape joint at the ceiling and wall junction on partitions near the center of the truss span. If the truss is connected rigidly to the to the top plate of the partition wall it can even lift the wall revealing a gap under the baseboards.

truss-uplift
Two items need to be addressed during construction to prevent problems caused by truss uplift. First the partitions should be connected to the truss bottom chord with a slotted ‘L’ bracket to allow vertical movement of the truss. Secondly the ceiling drywall should not be connected to the truss within 18" of the partitions. The simple use of 2×6 blocking on top of the 2×4 wall plate will provide a fastening point for the drywall which will stay with the wall. The ceiling drywall will flex from the blocking to the first fastener to the truss.

After two years all your lumber has settled and your house should not be moving either. Some houses will settle more than others. New homes are required to be built on un-disturbed soil but when building sub-divisions, who is there to ensure the ground level was not altered exactly where your house was built?

If you are not willing to have possible humps in your floors I would recommend upgrading to the engineered floor systems. Some builders offer Silent Floors as one of many upgrades thrown in when the real estate market tightens up a bit.

When the builder does come in after your one year period is over to repair those drywall cracks, pay attention to what he is doing. Some builders will want to trim your door rather than re-level your frame. This is totally up to you but I would rather have a square door than one which has been trimmed to fit a jamb that is no longer square.

Written by Roger Frost 

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Concrete Crack Repair – Types and Methods

Polyurethane Foams for Low Pressure Injection Crack Repair

What is the better choice: polyurethane or epoxy? Epoxy is the better choice if structural strength is required to be maintained. If the crack is only repaired to prevent water leakage then either product can accomplish this task.

Cause of Cracks

Lack of joints, to accommodate drying shrinkage and thermal movement during the construction phase is one of the major causes of concrete cracks. Settlement and overloading are also common causes of cracking. Cracks usually appear within the first month after construction. These cracks can leak as soon as they are formed or might expand and leak later. Crack can grow and cause problems as they expand.

How Cracks Grow

Moisture, which is the worst enemy of homes, enters the tiny cracks in the concrete and in colder weather, freezes, enlarging the crack. Also, movement of soils surrounding your home, through settling, can also cause expansion of your cracks. In extreme cases, soils that are unstable can overcome the inherent strength of concrete causing crack and expansion.

Cracks caused by construction, heat, freezing and settlement can be corrected by injection. Cracks caused by unstable soils must have soil problem stabilized prior to attempting injection corrective methods.

Low Pressure Injection

This method of injecting polymers into the concrete is adequate for repairs of cracks not involving high volumes of water. High-pressure injection is better suited for this type of application. Low pressure is defined as injection pressures between 20 to 40 psi and can be used with either ports or surface injection. Pressures as high as 250 psi may be used.

High Pressure Injection

1,000 to 10,000 psi utilizing injection packers usually placed in holes drilled at 45 degrees to intersect the interior of the crack. This is common method of repair using polyurethane foam. High cost of packers, clean up of excess, potential stress damage and dangers of using high pressure are overcome by using low-pressure injection methods.

The use of surface ports (with one-way check valves) together with low-pressure injection of a sealed crack eliminates these problems in most situations. The injection of high-density foam is an effective water proofing method.

The best method for low-pressure crack repair is to slowly inject liquid polymer into crack until crack is completely filled, filling of adjacent surface port is visual confirmation. Using pressures above the 40-psi will allow polymer to rise and may indicate a false presence of the polymer filling voids.

Methods of Surface Sealing and Placing of Surface Ports

Surfaces are first cleaned with wire brush, and then surface ports are placed along crack at intervals equal to the thickness of the wall. The surface crack is then filled with epoxy paste which when sufficiently hardened allows filling of surface ports to begin. Hydraulic cement is used when cracks are actively “wet”. The ports must then be anchored to prevent blowing off during injection.

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Deck Collapse – Is Your Deck Safe?

Safety Alert: Study Reveals Sharp Increase in Deck Failures A landmark study reveals that there have been 179 reported deck collapses from January2000 through December 2006, killing 33 and injuring 1,122.By: Michael Morse, Brittney Corwin, Robert Morse and Andrew JohnsonIn September 2006, a particularly violent deck collapse occurred. What made this collapse so frightening was it occurred with surprisingly little impetus. The potential purchasers, a family of five, were doing a final walkthrough on a single-family house in a quiet, older subdivision in Lawrenceville, Georgia. The house was situated on a lot that sloped away from the street. The back sliding door was about 12’ above grade. There was a well built and well maintained 12’ by 15’ deck overlooking a wooded backyard. When the husband, wife, and two of their teenage children stepped out onto the deck, it pulled off the house… but it did not just fall down. As the deck pulled away from the house, the deck swung underneath, struck the outside support columns, and landed upside down. The family fell to the ground and the deck, now upside down, landed on top of them. They were trapped underneath the deck, injured and traumatized. Emergency services were called and the family was transported to the hospital. Fortunately, the deck’s guardrail acted like a roll bar and held the deck off the ground, preventing the victims from being crushed.Why did this happen? How could a solidly built structure just detach and collapse?
While the deck itself was structurally sound, the connection of the deck to the house was not. When the family walked onto the deck and then stopped, their momentum was transferred to the fasteners that held the deck to the house. That little bit of movement was just enough to overcome the friction holding the fasteners to the house rim joist. The deck simply pulled away from the house.
Since the deck was built to the standards prescribed by national building code, it was supposed to be capable of accommodating the weight of 48 people, but it only took four people to bring it down. Why?Scope of the problemThere is no reliable source for statistics on how many decks there are in the United States, how many decks are being built annually, or by whom. Several indirect approaches were used to generate reasonable estimates relating to deck construction and the number of decks there are in the United States. Information was collected referencing housing starts, home design trends, and the do-it-yourself market.Home BuildersGrowth of the decking industry is partly driven by sales of new homes. The National Association of Home Builders (NAHB) estimated housing starts in 2006 to be nearly 2 million units houses being built today new home options in 2006. This number does not include new decks installed on older homes, or renovations of older decks.Deck BuildersThe North American Deck and Rail Association (NADRA) estimates the annual retail installed value of deck components and accessories in the United States to have been between $9 and $10 billion in 2005 coming years. In fact, NADRA was started in response to this terrific growth. Based on a 2005 survey performed by national retailers, the average cost of a deck is approximately $11,300 decks were constructed in 2005 alone.HomeownersDeck construction appears to be simple and straight forward, and many homeowners undertake the project themselves. With readily available calculators, guides, and premade construction plans, it is easy to see why deck building has become one of the most common ‘do-it-yourself’ projects. Although this group makes a significant impact on the decking market, there was no apparent way to quantify its contribution.House Design InfluenceIn 2005, more than 60% of all new homes either came with a deck, or incorporated the opportunity for future outdoor living space delay the construction of a deck, the layout of the house includes, and anticipates, this future addition.While some homeowners may choose to Subdivisions, such as this town-house community, can be found across the United States. It is clear that these homes were designed to include a structure outside of the rear door. The rim joist located just below this door was intended to be the point of attachment for the future deck. Building CodesThe International Residential Code (IRC) is one of the primary references for both deck builders and code officials. It contains instructions on how to build reliable and safe structures. General requirements for all structures, including decks, are in Chapter 3, Section R301 Design Criteria. This section states that: “Buildings and structures, and all parts thereof, shall be constructed to safely support all loads, including dead loads, live loads, roof loads, flood loads, snow loads, wind loads and seismic loads as prescribed by this code. The construction of building and structures shall result in a system that provides a complete load path capable of transferring all loads from their point of origin through the load-resisting elements to the foundation.”Specifications concerning decks are found in the chapter on floors (Chapter 5) of the IRC. One section that is written specifically for decks (R502.2.2 Decks), provides a very brief and non-prescriptive recap on how decks must be attached and supported. “Where supported by attachment to an exterior wall, decks shall be positively anchored to the primary structure and designed for both vertical and lateral loads as applicable. Such attachment shall not be accomplished by the use of toenails or nails subject to withdrawal. Where positive connection to the primary building structure cannot be verified during inspection, decks shall be self-supporting.”All other guidance must be derived from sections that do not specifically cite deck construction. They are written with house building, not deck building, in mind.The Study of Reported Deck CollapsesThis study seeks to better define the scope of deck failures in the United States by providing statistical evidence of the problem. This report includes deck, porch, and associated collapses that were reported from January 2000 through the end of 2006. Although a few Internet sites referenced deck failures, no central source of data was found.MethodologyUntil now, conclusions drawn on deck collapse were based on a very limited sample size. This report hopes to establish a database with a statistically significant sample size, and to then identify trends, characteristics, or weaknesses. In order to draw accurate conclusions on deck failure, there must be adequate data to analyze.Deck collapse or deck failure, for the purpose of this report, is defined as a single negative structural event that renders a deck non-functional. If a deck either detaches or shifts away from the primary structure, it would be included in the study.An incident report form was developed, completed, and archived for every collapse. Data sought for each event includes: the height and size of the deck, construction materials, occupancy and activity at time of collapse, and cause of failure. These data points were then analyzed to identify trends or patterns.The data used for this report was gathered through comprehensive searches of Internet and periodical archives using key phrases including deck collapse, deck injury, rail collapse, etc. Great care was taken to include all legitimate events; that is, events based on construction technique rather than an unrelated accident.Source of InformationThe primary source of information detailing deck collapses is the news media. News reports focus on injuries sustained rather than the actual cause of the event. Reporters reflect the statements of emergency responders or eye witnesses, neither of which are focused on the physics or engineering of the deck structure. The cause that was initially reported may be different than what a subsequent investigation would find. This lack of complete information can lead to flawed assumptions as to the cause of deck failure.Correcting the design defects that cause deck failure is impossible if solutions are based on inaccurate information. Deck collapses are reported as isolated events. Very little background information is provided on the scope of this problem. Subsequent reporting could include the reasons why decks go down in the United States. There have been news segments on building a better deck; however, there also should be reports on the actual causes of failures and segments on preventing deck collapse.Data, Trends, and Analysis DataFrom January 2000 through December 2006, there were 179 reports of deck and railing failure. In these events 1,938 people were exposed to injury; they were either on or under the deck when the failure occurred. Of those involved, 1,122 sustained injuries, and 33 people died. This translates into 58% of the people involved in reported deck and railing failure were injured or killed.Virtually no municipalities perform an investigation that documents the cause of the deck collapse. A smaller sample was used to investigate this trend. Out of all the collapses included in the subcategory, only one such report was found.TrendsAn examination of the data on reported deck collapses reveals several interesting trends. Deck collapses are increasing at an average rate of 21% per year. Twice the number of deck collapses occur as compared to the rest of the year.There is a well-defined deck collapse season (June through August) in which over. Virtually all reported deck collapses occur while the deck is occupied. AnalysisAn analysis of the data and trends for deck collapse has led to the following observations.DECK CONSTRUCTIONReported deck collapse. This type of failure includes the separation of the rim joist from the house floor joists, the separation of the ledger board from the rim joist, and the separation of the ledger board from deck joists.Failure of the house to deck ledger connection accounted for over 90% of all deck collapses. Decks are built to the same codes and standards that houses are, yet decks are more prone to collapse. Current deck connections and/or the deck components are subject to failure long before the end of the service life of the deck. Follow up investigative reports on the cause of collapses are rarely generated.Ninety-five percent of reported collapses occurred when the decks were occupied.ConclusionAre there right ways (or, more importantly, wrong ways) to build decks? Is anyone watching?An analysis of deck collapse data indicates that deck connections are subject to failure long before the end of the service life of the other components of the deck. The lack of structural redundancy, especially at the critical connection points, leads to deck collapse.Specifically, deck collapse is related to the connection assembly of the deck ledger board to the house substructure. In the scenario where the house was built to accommodate a deck, it is assumed that the floor joist system of the house was constructed to support a deck. This intention was known by the architect, the builder, and the homeowner. Was it known by the framing contractor? A better question is: did the framer prepare the point of attachment (the rim joist) for the loads associated with a deck in use? Can this rim joist resist the pull out force exerted by a deck, no matter how large?When a deck collapses, people are injured, or worse. A design flaw in deck construction may lead to these catastrophic events. One can disagree with the process used to estimate the number of decks being built, but the underlying fact is that the growing number of decks in existence will directly translate into a proportionally larger number of collapses, which presents a significant public health risk.When a deck is bolted to a house, the strength and durability of this attachment depends primarily on the ability of the rim joist of the house to transfer the load to the house foundation. Unfortunately, the rim joist was not designed to resist the pullout action imposed by a deck. Current building codes provide details for the installation of rim boards. These details are the same whether or not a deck is to be attached. Building codes should require additional anchoring for the rim joist when constructing decks and/or houses onto which decks will most likely be attached.As with any new development, there is a learning curve to discover the long-term performance of a product. The shortcomings of current deck construction must be studied, understood, and addressed. A factor that complicates this process is the incredible number of new decking products and techniques that are constantly being introduced. There is no time to slow down and evaluate the effect that one individual product or new technique has on the overall structural performance. With new products and new techniques being introduced so quickly, there is no easy way to generate a base line of deck performance against which to evaluate change.The popularity of outdoor living space is growing despite the increasing number of deck collapses. There is a perception that each collapse is an isolated event that is dependant on the quality of the deck builder, as opposed to part of a larger trend predicated on a design or structural flaw of the deck’s critical connections.The public is not aware of the increasing danger associated with deck failure, largely because of a lack of conclusive data. A central database is needed to collect and analyze reports on deck collapses, the cause of the collapse, the number and severity of injuries, and the associated costs. Only after this information is assembled can the effect on public safety be evaluated and addressed.A central database is now being created to allow for the archiving of deck collapse events. The purpose of this new database is to provide information for the further study of deck collapses.A Bad WinterThe winter of 1996 saw an unusual amount of snowfall in North Dakota. As it continued to snow in the Fargo area, a repetitive phenomenon occurred: deck after deck collapsed under the weight of the accumulating snow.The number of collapses intrigued a local deck builder. Mr. Todd Funfar, President of Deck Masters, began keeping a photographic log of deck failures. He cataloged over eighty separate collapses that occurred during the winter of 1996.A review of his photographs leads to the following observations:.The deck detached from the house foundation, either from the house band board or from the outside support beams, and then dropped. This suggests that the deck joist system was capable of carrying loads greater than the capacity of the ledger connection and/or outside load beam connection.Rather than the deck floor joists breaking mid-span, decks simply detached from house.The loads increased very slowly and over an extended period of time. As it snowed, the weight grew greater, exerting a sustained load on the decks throughout the winter months. Normally, loads on a deck are applied quickly and for a much shorter period.Due to adverse weather conditions, this series of collapses occurred without the condition. Heat from the house would induce snowmelt adjacent to the ledger board. .The most common point of failure was the connection of the ledger board to the house. While the mechanics of ledger failure varied, the result was the same; the assembly that links the deck and the house floor joists failed, causing the deck to collapse. With the Fargo collapses, the conclusion that can be drawn is that the connection of the deck to the house was not adequate to transfer the loads from the deck, through the boards and hardware, to the foundation of the house.As an aside, while researching reports of deck collapses (covering hundreds and hundreds of hours in national archives and internet search engines) not one of the collapses from the North Dakota winter was discovered.

The deck connections and deck components were in a prolonged wet service.

Large Buildings and Fire Protection

 

Firestopping is installed mainly in large building but may be found in small residential multi-family units etc. Firestopping is installed in strategic locations to resist the passage of fire from one area to another.  One use of firestopping is to maintain the integrity of fires separations such as penetrations by pipes, wires or other building services.  The second purpose is to limit the size of concealed spaces as found in stud walls, attics, crawl spaces, and spaces in between the superstructure and exterior building envelope.

 

Firestop systems are rated based on tests in accordance with CAN4-S115-M, “Standard Method of Fire Tests of Firestop Systems. Four ratings ( F, FT, FH and FTH) are assigned based on test results.

 

Firewalls are a special type of masonry or concrete fire separation that subdivide a building into two or more entities with a fire-resistance rating from between 2 to 4 hours. Firewalls are usually used by designers to limit size of individual areas to allow for cheaper construction costs by eliminating need for expensive fire-protection equipment such as sprinklers etc. This procedure does not apply to fire alarm or detection system however as this is based on entire buildings “gross area.”

 

Flame Spread and Interior Finishes is the measurement of the surface characteristics of materials used in finishing buildings. Buildings are broken down into three categories which are combustible construction, non-combustible construction and high rise buildings. This is broken down into a further sub-category of whether building is sprinklered or not. The Ontario Building Code provides tables which provides the rules that govern finishes on walls, ceilings, surface – rating applies to surface only and cut test – which applies to any surface that can be exposed by cutting.

 

The importance of fire protection has been proven over and over again when lives have been lost in large buildings whose fire protection equipment has been either compromised or disabled for various reasons. One large fire in a high rise, which started in café on first floor, which contributed to lost lives, was blamed on missing fire-stopping. Such a small failure can have disastrous consequences.

 

This is our second article on large buildings based on requirements of the Ontario Building Code.  We will be endeavouring to provide basic information which we use on inspecting large buildings. Municipal inspectors are not permitted to inspect buildings that they do not hold qualifications for but there is no such restriction in place for commercial building inspectors.  Caveat Emptor – Buyer Beware

 

 

 

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