Structural
I am not an engineer, all views expressed in this post are based on my opinions and experiences. If you encounter anything that you are unsure about, consult with an engineer or contractor that specializes in structural repairs.
Structural work includes foundations, drainage, and framing. These areas of a house are often the least understood and most feared, and for good reason. Structural integrity is critical for any kind of measurable value, and it’s typically the most expensive type of renovation. While many finishes can be preserved during structural repairs, the work is inherently invasive and often requires rebuilding sections or systems in the affected areas. Because structural systems, defects, and repair methods vary widely, accurate cost estimates are nearly impossible. Costs can range from a few hundred dollars for a single footing and steel column to six figures for a full foundation rebuild. It is also impossible to estimate costs without knowing exactly what will need to be replaced after that work is completed. Structural work often does not produce a positive net value, especially for extensive rebuilds where the expense and disruption may exceed the value gained. For this reason, cost assumptions are secondary to identifying and performing only the necessary repairs. That being said, structural work is not an area to cut corners. While it’s possible to manage or perform much of the labor yourself, all work must meet or exceed minimum code requirements to ensure safety and avoid scrutiny. Extensive projects will require an engineer to design repairs and permits to oversee compliance. Often, particularly with framing, defects are uncovered that require localized repairs. When this occurs, it’s crucial to follow code requirements and best practices. Only conceal the area once repairs are properly completed using the correct methods and materials.
Quick Tip: Only work with structural engineers and contractors you trust. Home inspectors typically defer structural issues to engineers for liability reasons, and engineers, in turn, often recommend the most extensive repairs possible to protect themselves. Some may even refer you to a contractor, which itself is a questionable practice. Contractors, naturally, are inclined to suggest repairs since they are trying to sell a job. Left unchecked, this sequence can turn a minor hairline crack into a full foundation underpin. It’s essential to perform your own due diligence and verify the necessity and scope of any recommended work.
Foundations
There are many foundation types, but for this book we’ll group them into three main categories: basement, crawlspace, and slab. We will focus purely on structural symptoms in this chapter, and save moisture concerns for the drainage section. They all share a few core principles defined here, that I refer to throughout.
Footers and footings: Footers or footings are the widened, reinforced concrete bases that sit at the bottom of a foundation wall, pier, or column. Their job is to spread the structure’s weight over a larger area of soil so the building doesn’t settle, shift, or sink. Footings should be placed below frost depth and on stable soil (sand or gravel) to ensure long term stability.
Frost depth: Frost depth is the maximum depth in the soil at which groundwater is expected to freeze during the winter. This depth varies by climate and region and determines how deep footings and foundations must be placed to prevent movement or damage caused by soil expansion during freezing and thawing cycles.
Frost heave: Frost heave is the expansion and movement of moisture rich soil as it freezes. When water in the soil forms ice and ice lenses, the soil expands and exerts pressure in any direction where there is the least resistance. In open areas this shows up as upward heaving of slabs, walkways or even fence posts. When the soil is trapped against a basement or crawlspace wall, the expansion creates strong lateral pressure.
Expansive soil: Expansive soils are types of clay rich soils that swell significantly when they absorb moisture and shrink when they dry out. This constant cycle of expansion and contraction creates strong pressure on anything built over or against them. Expansive soils are a major cause of structural movement and foundation damage in many regions, especially where the soil contains high levels of montmorillonite clay. Homes built on expansive soils require proper drainage, moisture management, and sometimes engineered foundations to prevent shifting and cracking.
Hydrostatic pressure: Hydrostatic pressure is the force exerted by water when it builds up in the soil around a foundation. As the surrounding soil becomes saturated from rain, poor drainage, or a high water table, the water can’t drain away fast enough. This trapped water pushes outward, and sometimes upward through the slab.
Lateral pressure: Lateral pressure is the horizontal force pushing against a foundation wall, usually caused by soil and water. Unlike the vertical load of the house pressing downward, lateral pressure pushes inward on basement or crawlspace walls. When it becomes excessive, it can bow, crack, or even collapse a wall. This is the leading cause of horizontal cracks in a foundation. This is usually caused by frost heave, expansive soils and hydrostatic pressure.
Differential settlement: Differential settlement is when different parts of a building’s foundation settle into the ground at different rates or by different amounts. Instead of the structure moving uniformly, one section drops more than another, creating stress. This uneven movement leads to symptoms like stepped or widening cracks in walls, floors that slope, doors or windows that stick, or gaps opening between building elements. It’s more serious than uniform settlement because it indicates inconsistent soil support, moisture imbalance, or structural issues that can worsen over time if not corrected.
Point load: A point load is a concentrated force applied to a very specific, localized area of a structure, rather than being spread evenly over a surface. In building terms, it often occurs where a beam, column, or footing transfers the weight of a structural element, like a post, directly onto a single spot of the foundation or framing. Point loads must be properly supported and distributed to prevent excessive stress, cracking, or structural failure.
Underpinning: Underpinning is the process of strengthening or stabilizing an existing foundation by extending it to more stable soil or adding support beneath it. This is typically done when the original foundation is settling, shifting, or unable to carry the load of the structure. Common underpinning methods include installing concrete piers, helical piers, or steel push piers to transfer the building’s weight to deeper, more stable soil layers, effectively preventing further settlement and restoring structural stability.
Basements
Basements are my favorite type of foundation for several reasons. They make it easy to confirm the footing is below frost depth, and they’re far easier to access and inspect than other foundation types. Older homes with basements as opposed to crawlspaces and slabs are also more likely to be salvageable. The open space also makes running or repairing MEP’s (mechanical, electrical and plumbing) far simpler. Homeowners value basements for storage and the potential to add finished space, but they’re also the most expensive foundation type discussed in this book. Because basements often house the home’s MEP’s and are considered usable space, they’re usually held to a higher standard. Some older homes have stone basement foundations, later replaced in history by block or poured concrete. A stone foundation isn’t automatically inferior, if you’re looking at it today, it has likely performed just fine for more than a century. Sandstone can be problematic because its porosity allows it to wick and retain moisture easily. In some cases, the stone was stacked directly on the ground, which isn’t ideal, but even so, many of these foundations have remained stable for hundreds of years.
Inspecting basement foundations: Inspecting basement foundations focuses primarily on the blockwork or poured walls. Walk the perimeter inside and out, looking for cracks and displacement. Small cracks are normal, especially in older homes where settling has occurred and stabilized. Pay close attention to horizontal cracks, which are more concerning than vertical ones. For vertical cracks, note whether they widen toward the top, as this can indicate differential settlement. Displaced or offset cracks are also worrisome, signaling lateral pressure or movement beyond simple shrinkage or minor settling. Sight down the walls to check for bulging, and be aware that plaster or mortar may be used to conceal problem areas. Even if shifting has stopped, cosmetic repairs often aren’t sufficient for resale unless the seller can provide documentation showing the work was properly performed.
The next areas to inspect are the point loads. Steel columns are often installed through the middle of the structure to transfer weight down onto footings. While you usually won’t see the footings because they’re buried under the slab, you can check the base of the posts, if they’re embedded in concrete, they’re likely sitting on a proper footing below. In older homes, it’s common to find temporary jack posts placed on top of the concrete, added to support sagging beams or headered joists. This is technically an improper repair, since a footing is needed to prevent punch through from overloading the slab. However, if there are no signs of cracking or displacement under the column and the work appears reasonably aged, it’s generally not a major concern. Footings should always be poured for new columns, but the widespread homeowner practice of skipping them makes this a common, often tolerated issue. Inspect the post bases for corrosion, which can compromise structural integrity, and watch for wooden posts sitting directly on concrete or dirt, as they can wick moisture, rot and compress over time, causing further sagging.
If there is a slab, inspect it for cracking, as this can indicate heaving from expansive soils or hydrostatic pressure. Cracks up to about ⅛ inch are typical in most slabs, but when one section is raised above another, it can signal a more serious problem, especially if paired with issues in the foundation walls. Displacement confined to the slab alone is generally less concerning and may result from poor compaction or suboptimal subgrade material. If the cracks are no longer widening or shifting, they are often tolerable.
Once you’ve gathered evidence of foundation movement, compare it with signs throughout the rest of the house. Check for cracks in drywall, particularly above doors and windows, and inspect siding, soffits, and trim for separation caused by settling. You may also find corresponding cracks or gaps in brickwork and other attached masonry. These observations can help estimate the age of the movement and indicate whether it has likely stabilized. Assessing this accurately is challenging, and a fair, unbiased structural engineer can provide valuable guidance.
Crawlspaces
Crawlspaces can be a major concern, especially in older homes. They were a common building method before improvements in concrete technology made slab on grade construction standard. Many older crawlspace homes were built with DIY methods or cost cutting shortcuts, often sacrificing proper building practices. Footings are sometimes less than a foot deep, which is far shallower than the 32”-36” of frost depth in my area, and block walls may sit directly on the soil. Another significant issue is the close proximity of framing to the ground, which allows moisture to accumulate and gradually degrade the lumber. Never consider buying a crawlspace home without thoroughly inspecting the crawlspace.
Inspecting crawlspace foundations: Be attentive when walking through a crawlspace house, feeling for signs of shifting in the floor planes. As you move from room to room, notice if the slope of the floor changes between sections, this is often the first warning of structural issues. Accessing the crawlspace is essential. In older homes, you may not be able to enter due to lack of an access point or low clearance. If you feel moderate floor sloping, it’s prudent to budget for structural repairs, as they will almost certainly be needed.
Once inside the crawlspace, inspect the perimeter as you would a basement foundation, checking for cracks and displacement. Pay special attention to point loads and continuous pier walls running down the middle of the structure, which are often resting directly on shallow soil prone to heaving or washout. Look carefully for signs of flooding. Persistent moisture is extremely damaging to framing and will often affect the foundation. Indicators include hard, compacted depressions that remain damp, rotting framing members, and small holes suggesting termite or insect activity.
Slab on grade foundations
Slab on grade foundations are simpler and generally lower risk than crawlspaces and basements because there’s no below grade wall to crack, leak, or bow, and no exposed framing that can rot from moisture. Proper grading is extremely important for slabs. At minimum, you want the standard 6 inches of fall over the first 10 feet as you move away from the house, and more if soils are expansive or the lot holds water. The main concerns with slabs are settlement, heaving from expansive soils, and plumbing leaks embedded in the concrete. Ductwork can also be buried under the slab, and this can be a major concern if water isn’t properly mitigated.
Inspecting slab on grade foundations: A slab on grade inspection starts with walking the full exterior perimeter to look for cracks, displacement, erosion, or undermining, and to confirm that grading and drainage move water away from the structure. Inside, your slab will likely be concealed by finishes, so you must be keen on investigating the covering material for signs of settlement or moisture. Most slab evaluation ends up being indirect, you rely on floor movement, door and window operation, cracks in finishes, and exterior clues at the slab edge. Check the floor for sloping, humps, dips, and cracks. Look for moisture issues such as damp spots, efflorescence, musty odors, or swollen baseboards, and check for gaps or distortion where the slab meets interior walls and doors. Pay close attention to areas around plumbing fixtures for localized sinking that might indicate a slab leak. From outside, note any tree related movement near slab edges.
When to repair foundations
It is difficult to generalize foundation repairs because it often requires monitoring cracks over several years, taking into account both their size and the age of the home. Also, the first step in addressing foundation issues is ensuring all drainage requirements are met. Often, simply controlling water is enough to stabilize the foundation. The next chapter will cover drainage in depth, but this section focuses specifically on methods for structural correction.
Vertical cracks: Cracks under ⅛ inch typically require no action unless you know they are recent. Cracks up to ¼ inch often only warrant monitoring, particularly in older homes, as they are fairly common. However, multiple cracks showing continued progression, even after drainage corrections, may indicate the need to underpin all or part of the foundation.
Horizontal cracks: Horizontal cracks and displacement demand immediate attention. If the tilt exceeds 1” over the full height of the wall, it is often deemed unsafe. Common repairs include installing wall anchors or tiebacks to pull the wall back into place, bonding carbon fiber straps to reinforce masonry, or adding bracing or deadman anchors to resist soil pressure. In severe cases, helical or push piers can stabilize the foundation, and rebuilding or partial replacement may be necessary if integrity is lost. Correcting drainage and soil conditions around the foundation during this process is also critical, since water pressure is often the underlying cause. Cosmetic fixes alone, like filling cracks, won’t stop movement and should never be relied on as a solution.
Mud jacking is a slab lifting technique in which a slurry mixture is pumped beneath a settled concrete slab to raise it toward its original level. The injected material fills voids and lifts the slab, but it is not a substitute for underpinning a slab on grade foundation. Pouring a new concrete overlay is also common, though it is only appropriate when the slab is stable and there are no voids beneath, as added weight could otherwise cause problems. These methods are often combined to both stabilize the slab and achieve a level, usable surface.
Jacking the foundation: This should only be done once the structure is stable and any causes of settlement have been addressed, like poor drainage, soil issues, or plumbing leaks. The process involves placing hydraulic or screw jacks under load bearing beams or walls and raising the structure slowly and evenly in small increments, alternating jacks to avoid twisting or cracking. Once the desired height is reached, permanent supports such as steel piers or footings are installed to hold the foundation in place. Careful monitoring for cracks or movement during the lift is essential, and a licensed structural engineer should design or supervise the operation to ensure safety. Complex foundation repairs are not beginner friendly projects, so it’s probably best to hire a professional if your project involves jacking the foundation.
Pouring footings and adding support columns: This may be required to support over spanned beams or damaged framing, but it is generally much less expensive than large scale foundation repairs. A professional can help size the footing appropriately based on soil tests and calculated loads. As a safe rule of thumb, a footing measuring 30” by 30”, 12” thick, with 6” of compacted gravel and reinforced with rebar, will over engineer the footing for most typical residential applications. Always make sure your footings are installed below frost depth, and always follow the manufacturer’s instructions when installing the steel column.
Unsupported stairwell headers: It’s very common to see sagging around stairwells in older homes because the original header joists were often undersized. Correcting this usually means adding a properly sized steel column on an adequate footing to stop further movement. In some cases you can gently jack the area to recover part of the sag, but this has to be done slowly and safely. The proper method is to pour a footing, set the adjustable steel column in place, then use a bottle jack and a temporary 4×4 post to apply upward pressure to the joist. Raise the section gradually, no more than about an eighth to a quarter inch per day, to avoid cracking finishes or unloading adjacent supports. Once the height is where you want it, lock the steel column in position.
Chimney as a point load: Most houses over 100 years old relied on the chimney as a structural support point. That’s a problem because chimneys are extremely heavy and prone to settling, which can create noticeable slopes in the floors framed into them. Modern code requires a gap between chimneys and framing, but many old homes have joists sitting directly on the masonry. Even without fire exposure, those joists can rot from the moisture the chimney collects and releases, especially if the chimney is unlined.
Drainage
Proper drainage is the single most important factor in protecting a home’s foundation and preventing costly structural repairs. Water is the primary cause of settlement, heaving, and lateral pressure issues that compromise slabs, crawlspaces, and basements alike. Even the best built foundation will fail over time if water is allowed to pool near or under the structure. Before undertaking any structural repairs, addressing grading, gutters, downspouts, and drainage is essential. Diverting water from the house often stops movement and preserves the integrity of the foundation, reducing or even eliminating the need for more invasive corrective measures.
Inspecting for drainage issues If you notice cracks or movement in a foundation, your first step should be to check for improper drainage or poor grading. A negative grade that slopes toward the house is a major red flag, and whenever I see it, I immediately expect foundation issues in that area. I also look for evidence of past repairs to gauge whether the problem has already been addressed. Newer PVC cleanouts or standpipes near downspouts often indicate that drainage work has been done, and these are commonly paired with a trench of gravel showing where excavation occurred. Conversely, if the yard feels spongy or stays saturated after normal weather, you can safely assume the drainage system is either inadequate or nonexistent.
From inside the basement, you can often find clear evidence of moisture intrusion. Smell the air, musty odors almost always signal moisture, even if it isn’t immediately visible. Start by inspecting the lower portions of the walls and slab, where water typically first appears.
- Look for efflorescence (white, chalky deposits), which is one of the most reliable signs of chronic seepage.
- Check for discoloration, peeling paint, or bubbling drywall in finished basements.
- Pay close attention to corners, where the wall meets the floor, and areas around penetrations such as plumbing or buried conduit. These are the likely infiltration points.
- Hairline cracks with staining or darkened edges usually indicate active moisture flow.
- Inspect mechanicals for rust streaks on furnace legs, water heater bases, or other metal components in contact with the floor.
- Examine baseboards or wood in contact with the slab for swelling, rot, or mold growth.
- Water often leaves visible trails where it has run down walls or pushed up through cold joints in the floor.
- Many people apply sealants to basement walls (Drylok), but stark white walls can indicate a half measured attempt at repair. Without proper drainage, these coatings will eventually fail, and the basement will likely continue to leak.
How to address drainage
Proper drainage begins with the gutters and downspouts. It is essential to ensure gutters are functioning correctly and that downspouts carry water well away from the foundation. At a minimum, downspouts should discharge at least five feet from the house, and even farther if the yard lacks proper grading. In many cases, faulty or poorly routed gutters are the primary cause of basement and foundation moisture intrusion.
Once gutters and downspouts are functioning properly, the next step is to evaluate the grading around the house. In some cases, this can be addressed by filling low spots to create a consistent slope that directs water away from the foundation.
Sometimes grading alone isn’t enough due to the surrounding topography, and some form of drainage is required. A French drain outside the house is essentially an engineered pathway that collects and redirects surface or groundwater away from the foundation. It usually consists of a perforated pipe laid in a trench filled with gravel, often wrapped in fabric to prevent sediment from clogging the pipe. Water from the surrounding soil enters the gravel filled trench, flows into the pipe, and is carried to a safe discharge point, such as a storm drain, dry well, or lower area of the property. By intercepting water before it reaches the foundation, a French drain prevents pooling and reduces hydrostatic pressure that can cause basement leaks or crawlspace moisture problems. With proper research and materials, this is a project that can be completed by a knowledgeable DIYer.
A footer drain, also called a perimeter drain or foundation drain, is a drainage system installed at the base of a foundation wall to relieve water pressure and carry groundwater away from the structure. It typically consists of a perforated pipe laid alongside the footing, surrounded by gravel. The system collects water that accumulates around the foundation and directs it to a sump pit, daylight outlet, or storm drainage system. Homes built before the 1950s often lack foundation drainage, making them more susceptible to damage from moisture saturation.
Retrofitting a drainage system is frequently the most effective way to address the effects of water at the foundation. This type of system is also a kind of French drain. When installed inside a basement, it functions like a footer drain, except it diverts water from the interior rather than the exterior of the foundation. Interior French drains are popular because they require minimal excavation and are significantly less expensive than digging down to the footer from the outside. It’s critical not to damage the footer (if there is one) when jack hammering or saw cutting the slab to trench for a drainage system. You should be able to jack hammer the slab and leave the portion of the footer below it intact as long as you are careful not to run it too deep. Some footer edges are messy and unformed, so you may not end up with a clean profile to work with. Your perforated pipe should lay in front of the footer, on two inches of gravel. Best practice is to install drainage matting along the foundation wall, extending down into the trench, to channel any water seeping through the wall directly into the drain. This approach is highly effective and is my preferred method whenever I encounter moisture intrusion in a basement.
Exterior waterproofing involves excavating around the foundation to expose the walls and applying a waterproof membrane or coating to prevent water from entering. This method is highly effective because it stops moisture before it reaches the foundation interior. This is the most expensive approach to waterproofing the foundation and may be overkill depending on the circumstance. There are usually simpler and more cost effective measures to employ first. As a result, exterior waterproofing is usually only practical when the foundation is already exposed for a full or partial rebuild.
Framing
The framing is probably my favorite component of a house. When people talk about a place having “good bones,” they’re almost always talking about the framing. There’s no ROI angle here, framing repairs either need to be done or they don’t, and theyre usually a part of different standalone projects, so It’s too fundamental to ignore, so the focus isn’t on whether it pays back, but on making sure the structure is sound. In older homes especially, you’ll run into quirks and defects that require attention. Here we’ll focus on how to recognize common framing problems and how to repair them efficiently when they arise.
A pick test is a simple way to assess whether a wood framing member has begun to rot. You use a sharp tool, typically a screwdriver or knife, and press or “pick” into the wood to gauge its hardness and fiber condition. Sound wood will resist penetration, and the fibers will splinter cleanly. Rotted wood lets the tool sink in easily, feels soft or spongy, and the fibers pull apart in stringy chunks instead of crisp splinters. The deeper the tool sinks and the more the fibers crumble, the more advanced the decay.
Deflection is the amount a structural member bends, sags, or moves under load. Every beam, joist, or rafter will flex a little when weight is applied, but deflection becomes a concern when the movement exceeds what the structure was designed to handle. Excessive deflection can show up as bouncy floors, sagging ceilings, uneven surfaces, or visible bowing in the framing.
Sistering is a repair method where a new framing member (usually a joist, rafter, or stud) is installed alongside an existing one to reinforce it. The new piece is fastened tightly to the old member so the two act together structurally. Sistering is used to correct deflection, strengthen damaged or undersized framing, support cut or notched members, or bridge areas weakened by rot or insects. In most cases, the sistered member spans as far as possible past the damaged area and is attached to create a rigid, unified section. Inspectors may require the sister board to run the full span when the board it is reinforcing has lost enough structural integrity. It’s a straightforward, cost effective way to restore strength without fully removing or replacing the original framing.
Inspecting the framing
Rot is the single most critical framing defect to watch for. It’s what ultimately destroys a house once the weather barrier fails and moisture penetrates the structure. Crawlspaces are particularly vulnerable because of the framing’s proximity to the ground. In the earlier story about the crawlspace house I bought, the floor collapse was the result of widespread rot in the beams and joists. Poor building practices and accidental damage to framing from plumbing, HVAC, or electrical work are also common, hence the saying, “there’s nothing more dangerous than a plumber with a sawzall”. Houses rarely fail all at once. Damage to the structural web destroys the house slowly, causing sagging, shifting, and distortion until rooms become unusable or the structure itself is compromised. The good news is that the house usually gives warning signs before it reaches this stage, you just need to know what to look for.
- When a crawlspace or basement floods, the moisture condenses on the bottom of the framing members and degrades the lumber from the bottom. Always pick test the bottoms of the joists and beams to determine their salvageability.
- Look for signs of insect activity. Tiny holes in the lumber, mud tubes, and channels eaten through the wood. Moisture attracts insects to wood because it makes it easier to penetrate and consume.
- Check for deflection in the joists. The most reliable method I’ve found is using a laser level. Measure down to the laser line at each end of the joist, then measure at the midpoint. Because older homes are rarely perfectly level, take the two end measurements and use their median as the expected midpoint height. The difference between that expected value and the actual midpoint measurement is your deflection. Anything over about ½” is worth noting. In a 100 year old house, around an inch of sag over a long span isn’t unusual and doesn’t always require repair. But if deflection is remarkably greater than an inch over roughly 14 feet, reinforcement or added support is usually necessary.
- Look for notches in the joists or beams. This is one of the most common causes of deflection in older homes. In many cases, channels were carved into the tops of joists to retrofit electrical or plumbing into houses built before those systems were standard. Some notches are harmless, shallow cuts near the ends of joists usually don’t affect structural performance. But deep, wide, or mid span notches can weaken the member significantly. When the notch removes too much material or is located in the wrong part of the span, the joist will often need to be sistered to prevent further sagging.
- Check framed walls for plumbness. It sounds extreme, but I’ve actually come across a load bearing wall that was leaning so far out of plumb it had to be rebuilt entirely. The odd additions and questionable framing techniques that caused it aren’t worth detailing here, just know that it can happen. You want to train your eye to catch subtle structural issues. Older homes are almost never perfectly plumb, even being out by an inch over the full height of the wall isn’t unusual or immediately concerning. If the lean is obvious without measuring, or the wall visibly tilts, it’s time to plan on rebuilding or reframing that section.
- Inspect framing where it rests directly on masonry, particularly porous stone. Joist ends in direct contact with the foundation are highly susceptible to rot and can deteriorate completely over time.
- Inspect sheathing, subfloor, and roof decking, particularly OSB, which is less forgiving of moisture. Check for soft spots, swelling, or delamination. Wall sheathing can absorb moisture, causing it to expand and distort exterior siding, which may lead to buckling, gaps, or misaligned boards. Subfloor and roof decking can similarly swell or sag when wet, compromising structural integrity and making floors or the roof plane uneven. Pay close attention around roof penetrations, plumbing, and areas prone to leaks, as these are the most common points where OSB degrades quickly.
- Look for a history of past problems. Charred, water stained, or moldy wood, as well as replaced framing members, can indicate previous structural compromise. It’s important to examine any repairs closely to ensure they were done correctly and that the underlying issue has been fully addressed, rather than being a recurring or persistent problem.
- When inspecting framing, start by checking for proper bearing of structural members. Every beam, joist, or rafter should rest on an appropriate support, such as a post, sill plate, or load bearing wall. Understanding point loads and load paths helps identify subtle defects, like undersized or improperly seated members, which may not be obvious at first.
Repairing the framing
It’s necessary to repair framing when it’s rotted, damaged, or simply inadequate for the loads it’s supposed to carry. The fix can be as simple as sistering a few joists or as complex as rebuilding entire sections. I’ll break the topic into sections to keep it more digestible.
Repairing or adding beams: This will usually require temporary support to carry the load while you remove the material to prepare the placement of the beam. This temporary wall will be installed on one or both sides of the area, usually about a foot or two back. You can also use the opportunity to jack up sagging areas, although this will only allow you to reclaim so much. It’s important to consult the span tables for your species and size of lumber to know what is required for the given application. Repairing load bearing walls will usually require a similar process, but instead of installing a beam, you rebuild the wall under the affected area.
Repairing or replacing floors: Uneven floors are the bane of my existence. Every old house has them somewhere. The right repair depends first on the condition of the framing. If many of the joists are rotten and the floor has sagged beyond what’s reasonable to correct, a full rebuild is usually the only real option. I’ve done two full floor rebuilds this year, and neither was cheap or easy. The end result is a nearly flat floor that makes finishing easier and makes the house feel newer. Sometimes the decision isn’t straightforward, so I’ll use my most recent repair as an example of how I approach the evaluation.
Example: I recently rebuilt the first floor of an 1860 house with a sandstone foundation. Parts of the floor were collapsing into the basement because the sandstone had destroyed the joist ends, there was no sill plate, and the bearing was inadequate. The subfloor had cupped and warped so severely that nothing was salvageable. I ended up removing every joist and rebuilding the entire floor system, since patching sections wouldn’t have produced a reliable or high quality result. The rebuild also gave me the opportunity to extend the bearing by epoxy bolting a treated ledger to the stone and installing a treated sill plate to protect the new joists. This repair was reviewed and approved by the building department.
On the second floor, I was able to take a more localized approach because most of the joists were still structurally sound. The floor had significant sloping and the plank subfloor was heavily scalloped. This was caused by a combination of excessive mid span notching for retrofitted plumbing and electrical, along with overloaded beams that had sagged over time. The repair involved extensive sistering, installing two large beams, and adding several supporting members to properly transfer the loads down to new footings. After the structure was reinforced, the oak subfloor was planed to reduce the scalloping, making it flat enough for carpet. It wouldn’t have been suitable for a floating floor, but it was the appropriate repair given the circumstance.
Sistering damaged framing: Sistering is a common method for reinforcing damaged or weakened framing, and the exact requirements can vary widely depending on the severity of the damage and local building codes. In some cases, a small section of sistering is sufficient, just enough to reinforce a notched or slightly weakened area. These short sisters may be nailed and glued, and don’t need to extend all the way to the joist ends. On the other end of the spectrum, if a joist has been significantly compromised by rot or structural failure, a full length sister that bears properly on both ends may be required to fully restore load capacity. Because practices and code requirements can vary so much, from minimal reinforcement to full length load bearing sisters, it’s important to consult local building regulations or your inspector before proceeding with any sistering project.