Monthly Archives: May 2012
Thursday, May 31st, 2012
Written by: carmstrong
By Jerod B. Faris
Building type:
Single-family residence
Issues:
Beam pocket blow-out at top of foundation wall
Diagnosis:
Top of foundation wall is experiencing lateral movement from the backfill
Solution:
Recommend installing an interior buttress to provide intermediate support to foundation wall
The Problem and Diagnosis
When drywall began cracking in the finished basement of a residential home, the homeowners contacted SBSA’s staff for an evaluation. We performed an evaluation of the exterior and interior of the home, as well as a relative level survey. Level surveys help determine if there’s any vertical foundation or floor movement occurring in the basement and the garage.
During the investigation, SBSA discovered multiple exterior locations where the main floor beams were punching through the exterior foundation. This is a common sign that the top of the foundation wall is rotating inwardly as a result of lateral loads from the soils. After evaluating the interior distress and level survey results, SBSA concluded that the damage to the home was a result of this lateral wall movement, not vertical foundation movement.
Two counterforts were installed along this foundation wall as part of the original foundation design. Typically 3 – 4 feet in length, counterforts are installed on the exterior of the foundation, perpendicular to the wall near its mid-span. As the lateral loads from the soil try to push the foundation wall in, the counterforts are designed to hold the wall back. In this case, the counterforts were not sufficiently preventing the walls from moving inward. It was this inward movement that was causing the cracking in the drywall that the homeowners were seeing.
The Repair
To repair this condition, SBSA recommended abandoning the exterior counterfort design and replacing it with an interior buttress. Buttresses are wall supports identical to counterforts except they are installed on the interior of the foundation. While buttresses are more inconvenient and intrusive for the homeowners—since they encroach on the finished space—SBSA prefers using buttresses for supporting foundation walls in Colorado.
Since Colorado has expansive soils, any heave of the soils around a counterfort will cause the counterfort to push against the exterior of the foundation wall, increasing—rather than decreasing—the inward rotation of the foundation walls. When soils heave around a buttress, the buttress pushes back against the interior of the foundation wall in the opposite direction as the loads are imposed by the exterior soils.
Cutaway view showing a counterfort and buttress.
Green arrows show forces from soil heave from below; blue arrows show forces from lateral soils. Counterforts help to resist these forces, reducing the amount of deflection.
Green arrows show forces from soil heave from below; blue arrows show forces from lateral soils. Together, the deflection of the wall increases if only a counterfort is used.
Tuesday, May 22nd, 2012
Written by: carmstrong
By Ethan McKee
Mold in attic after re-roofing.
Building type:
Single-family residence
Issues:
Mold growth in attic
Diagnosis:
Attic vents covered during reroofing
Solution:
Remove and replace affected portions of roof sheathing. Reroof with adequate ventilation.
Moisture meter readings in the attic revealed that the humidity levels were elevated enough to sustain biogrowth.
When the homeowners had noticed dripping water and mold growth in the attic, they contacted SBSA for an evaluation of the cause and conditions.
Built in the 1970s, the original wood shake roof of the house had been recently replaced. SBSA performed the observation of the home on a clear and warm January day (65° F); the relative humidity outside the home was approximately 15%. Inside the attic, the relative humidity was as high as 67%.
At such a high relative humidity, the dew point—the temperature at which water condenses—was 54° F. When the temperature inside the attic got below 54° F, condensation formed and was causing the drips and mold that the homeowners reported. How did the attic get so humid?
Common household activities such as cooking, bathing, cleaning, and even breathing introduce water vapor into the air.
This water vapor permeates through holes and cracks in the ceiling and into the attic. The homeowners were not using humidifiers in the living space below, and the ventilation in the attic wasn’t adequate.
Roof underlayment removed; staining from moisture.
The attic ventilation had been sealed over when the new roof was installed, and no new ventilation was provided. Although the roof was not actually leaking, the vapor condensing on the inside left the roof sheathing dripping wet and mold was growing. Because this ventilation issue was detected within months of the roof replacement, structural damage to the wood framing was not yet an issue.
However, the roof sheathing needed to be replaced and extensive mold remediation of the framing was required. The brand new roof had to be removed and the roof rebuilt to include adequate ventilation. This example illustrates how changes that are meant to be improvements can actually create new, unintended problems.
SBSA can help prevent such unintended consequences through peer design review, effective new design, and construction quality assurance.
Moisture meter reading of the roofing sheathing.
Friday, May 11th, 2012
Written by: carmstrong
By Mary Jean McCarthy-Tapp
Type: Residential
Issues: Unprotected wood below-grade
Repairs: Remove and replace damaged sheathing, apply fluid-applied membrane along concrete foundation wall
SBSA was contacted to observe repairs to a handicap-accessible patio home. The patio slab had been poured flush with the door threshold in order to make the unit accessible. But the concrete was blocking the weep holes in the door’s sill pan. Consequently, water was leaking into the unit, buckling the wood floor inside.
Patio door providing rear access to a handicap-accessible patio home. The concrete slab patio was poured up to the level of the main floor without any thought given to protecting the vulnerable wood sheathing and rim joists below.
To perform the repair, the contractor jack-hammered out the concrete patio and removed the first row of hardboard siding. When the siding was removed, it quickly became apparent that this home was going to require more than a simple door repair and concrete replacement.
Buried below the concrete, the OSB sheathing, rim joists and sill plates were rotting away. One wall was covered in building felt below-grade, and the other had one layer of building paper for protection. The rim joists are part of the structure of the main floor. If they rot out, the wall that sits on top of them could fall down, creating a life-safety issue. Additionally, according to building codes, unprotected wood should not be in contact with grade.
To repair this condition, SBSA provided new details to the contractor to protect the vulnerable wood below grade. First, the damaged OSB sheathing and rim joists were replaced. Then a liquid-applied waterproof membrane was applied from eight-inches above the surface of the concrete to six-inches below the top of the concrete foundation wall. The patio door was reset in a sill pan flashing that was integrated with the liquid-applied waterproof membrane. After backfilling, the patio was re-poured and the siding and stone were installed with a two-inch clearance to the slab. Galvanized flashing and counter-flashing provide an extra layer of protection above the surface of the patio.
Rim joist stained and covered in biogrowth. The PVC pipe under the slab was supposed to drain the downspout, but it was backsloped, further compounding the problem.
Liquid-applied waterproof membrane installed over the repaired sheathing and rim joists. The site is ready for the concrete patio to be re-poured.
Friday, May 4th, 2012
Written by: carmstrong
By Justin Foy, R.S.
Case Study:
A reserve study was recently performed at a Homeowners Association that is 26 years old. During the observation, the following immediate concerns were noted.
A PVC roof system was used throughout the community. These roofs are 26 years old, and have exceeded their useful life. The seams had begun to fail, which can permit water to enter through the roof and potentially cause damage.
Repair: Replace roof, including underlayment and relevant flashings.
Estimated cost: $400,000.
The asphalt conditions throughout the community were also observed. Roads and driveways were experiencing distress, and needed to be replaced.
Repair: Remove asphalt, recondition the subsoils and to place a new asphalt system down
Estimated cost: $650,000.
The façades throughout the community are board and batten siding. The siding has become warped from moisture and needs to be replaced in order to continue providing a weatherproof exterior.
Repair: Remove board and batten siding, install new weather-resistive barrier, install new flashings and install new siding.
Estimated cost: $750,000.
Unfortunately, the association has roughly $500,000 in reserves and cannot cover these immediate needs. What are the Association’s options?
Option 1 – Defer the asphalt and siding projects and do the roof project.
Option 2 – Special assess the homeowners $1,200,000 at around $6,500 each and perform all of the necessary projects.
Option 3 – Pay for the roof project and have the association get a loan to cover the $1,200,000 needed for asphalt and siding project.
Option 4 (recommended) – Based on a risk analysis of the consequences associated with deferring any of these projects, the roof and the siding projects are necessary immediately. Moisture is penetrating into the buildings through the failed seams in the roof and areas of the façade. This is causing ongoing and progressive damage, as well as creating potential health risks.
Therefore, SBSA recommended replacing the roof using the available funds, special assessing each homeowner $3,700—which is much more manageable—for the siding replacement, and deferring the asphalt until the funds are built back up to afford the asphalt.
SBSA’s Construction & Property Analysis department can help associations determine the importance of various repairs and the potential risks associated with deferring certain repair needs. We take into consideration the available funding of the Association, and balance that with the existing conditions of the property.
Need a reserve study from SBSA? Download our reserve study proposal request form here.
