Your Homes Structure

Your Homes Structure.  One of the most frequent questions I am asked during a home inspection is if certain walls can be removed.  To answer that question it must be determined if the wall is load bearing.  A load-bearing wall is one that bears the weight and force of a structure, and transfers that weight to the ground.  As rule of thumb any wall on the first floor which is directly above a wall or structural beam in the basement must be considered load bearing.  If you have rafters then you will most likely have a supporting wall running parallel to the roof ridge to support your roof.

Point Load on Exterior WallPoint Load is the localization of the homes load to specific areas such as support walls, steel beams and foundations.  In a home you can follow the supporting load from the second floor right down to the basement, where the load is distributed down to the footings.  Older bungalows typically had a supporting wall built in the center of the basement with a poured footing below.  This wall support was then continued on the second floor with another supporting wall directly above basement supporting wall.  Any openings in these support walls requires a header designed to span codes of the Ontario Building Code to continue support for open area.

The use of truss construction has removed the need for supporting walls in the first floor of most bungalows.  The truss provides a clear span without the need for supporting structures and most subdivision homes now use trusses for roof support.  Read our recent article on trusses for more information.

 

The primary structure of the building provides a framework and the exterior supporting walls. The external cladding can be attached to this framework, usually via secondary steelwork. It is the primary structure which transmits the loads exerted on the cladding (wind, snow etc.) to the ground.  The entire structural load is distributed down to foundation walls and then to the footing.  In Ontario if your building lot is considered to be wet or on expansive soils such as clay, you will be required to double the size of your footings to provide the necessary support.  One other requirement is to build on undisturbed soil which does not require compaction.  Using machinery to level a foundation could cause settlement cracks in foundation due to the massive weight being supported by your footings.  Your local building department is responsible to ensure that contractors follow all applicable building code requirements.

 

Water intrusion can affect your homes supporting joists, whether visible or concealed above a ceiling.  A joist is typically made of dimensional lumber, although some products are also used. The purpose of the joist is to provide a nailing and support system for the floor sheathing and for the floor itself. The joist supports the live and dead loads placed on the floor assembly. TJIs (or the equivalent) are like mini wooden I-beams, with 2″x 2″ square stock on the top and bottom (chords), and plywood or oriented strand board (OSB) between the two. Attic or ceiling joists are used to provide floor support in attic spaces, and also help prevent the roof rafters from collapsing downward and pushing outward.

 

A  home’s roof is usually constructed of trusses or rafters.  A roof truss is a pre-engineered assembly of smaller individual framing components attached together and in a design suited to provide greater support and economy, as well as a faster installation time. It takes the place of rafters, attic (or ceiling) joists, and ridge beams, and is hoisted and nailed in place, forming the entire roof and attic structure. A roof truss spans the distance between exterior walls and requires no additional support. It is designed to take the guesswork out of field-framing for the connecting points for intricate or multiple rooflines, tray and cathedral ceilings, roof penetrations.

 

Many older homes and cottages have a visible sag in the roof line.  The middle of the roof may also have sagged. A lack of rafter ties (collar ties) can cause rafter spread, especially during heavy snows.  This often occurs near the middle of the ridge board, as outside walls keep the ends of the ridge supported.  Rafter spreading causes ridge sagging and can push the top parts of the walls out, especially during heavy snows.  Many older structures have a visibly bowed exterior walls and if still standing usually have support bolts passing completely through structure to provide support and prevent collapse.

 

Platform framing is the most used type of framing in modern homes.  The floor, or platform, is made up of joists that sit on supporting walls, beams or girders and covered with a plywood or OSB sub-floor. In the past, 1x planks set at 45 to the joists were used for the sub-floor. Floor joists can be engineered lumber trusses or I-beams that have increased rigidity and longer spans, with the added benefit of conserving natural resources. They allow easier access for runs of plumbing, HVAC, etc.  Balloon framing is no longer in use as this type of wall structure allowed fire in a wall to quickly spread to adjoining floors usually resulting in loss of whole structure.

 

Inspecting your homes foundation is a very important aspect of the home inspection and identifying locations and causes of cracks involves years of practice and knowledge. Diagonal cracks that grow in width, especially ones that are wider at the bottom than at the top, indicate settlement.  Diagonal cracks over windows indicate a weak header.  Diagonal cracks in a poured concrete foundation that are fairly uniform in width or are hairline-type are caused by shrinkage and, though they may allow water entry, do not constitute a structural defect.

crack in foundation - barrie home inspectorAny crack in your foundation is capable of allowing water to penetrate into your basement.  Hairline cracks are usually not considered a problem and the Tarion Home Warranty will not considered them an issue unless they are wider than 6mm or are actively leaking water.  Cracking can be the result of one or a combination of factors such as drying shrinkage, thermal contraction, restraint (external or internal) to shortening, sub grade settlement, and applied loads.   Cracks that occur before hardening usually are the result of settlement within the concrete mass, or shrinkage of the surface (plastic-shrinkage cracks) caused by loss of water while the concrete is still plastic.

The most accepted method of repairing a crack in the concrete is foam injection.  Foam is injected into the crack and expands and seals the crack preventing any water penetration.  The old method was to drill a home at a 45 degree angle into the crack and pump in foam under high pressure.  The newer method is to drill straight into the crack and inject the foam.   If you see a line of plugs protruding from a crack in your foundation with foam residue then this is the method that has been used to repair wall.

When planning any renovations involving your homes structure remember you must obtain a building permit and submit a plan for approval.  Most building departments will have a plan of your home on file and can assist you for minor projects, depending on the staff.  You may require the services of architect or registered designer to design a drawing for your building department.  Never remove walls without the proper approval or consulting a qualified person.

Your Qualified Home Inspector can provide you with information that will allow you to make an informed decision regarding removal of walls etc but you still should seek a professional advice before proceeding with any work. The Barrie Home Inspector is a Certified Building Code Official and has many years experience in reviewing designs and inspecting construction projects. We provide Construction Inspection services to Canada and USA.