Last year my company, New Dimension Construction, began restoring the exterior envelope of a neo-colonial home, in Millbrook, N.Y. The scope of work included tearing off an existing wood-shingle roof, replacing windows, and upgrading the siding and trim with more-durable materials. The house was only 28 years old, but poor trim detailing had caused the exterior cladding and windows to prematurely fail on many parts of the home. Making matters worse, the existing clapboard siding was not back-primed or installed on furring strips, which led to numerous issues with peeling paint over the years. Also, back-priming and the spot priming of end-cuts on the existing trim was not always done. For this story, I’m going to focus on a few of the trouble spots I encountered on this project—and continue to encounter on similar projects built around the same time period.


Trouble Spots


Failing trim. The cedar water table trim was rotted in numerous locations (A). Traditionally, water table was topped off with a wood drip cap, which makes it prone to rotting if regular maintenance painting is not kept up. And if, as was the case here, it has no metal flashing installed over the wood drip cap, it’s doomed to failure. The stepped-out corner boards suffered the same fate; wood drip cap allowed water to pool, causing the caps and the bottom of the corner-board trim to rot (B). At the gable-end stone chimney, a large gap opened up in the poorly constructed mortar joint between the chimney and house—loose rubble was used as backing for the wide mortar joint. Exacerbating the problem, the existing trim was scribed to the mortar and stone, making the gap larger and harder to repair as the joint began to disintegrate (C). The home’s existing fir gutters rotted where they were spliced together. The long runs of gutter were joined with 45-degree miter cuts, lapped with the short pieces of copper set in asphalt, which eventually gave way and leaked (D).
Failing trim. The cedar water table trim was rotted in numerous locations (A). Traditionally, water table was topped off with a wood drip cap, which makes it prone to rotting if regular maintenance painting is not kept up. And if, as was the case here, it has no metal flashing installed over the wood drip cap, it’s doomed to failure. The stepped-out corner boards suffered the same fate; wood drip cap allowed water to pool, causing the caps and the bottom of the corner-board trim to rot (B). At the gable-end stone chimney, a large gap opened up in the poorly constructed mortar joint between the chimney and house—loose rubble was used as backing for the wide mortar joint. Exacerbating the problem, the existing trim was scribed to the mortar and stone, making the gap larger and harder to repair as the joint began to disintegrate (C). The home’s existing fir gutters rotted where they were spliced together. The long runs of gutter were joined with 45-degree miter cuts, lapped with the short pieces of copper set in asphalt, which eventually gave way and leaked (D).


Failing windows. To begin with, on the windows, the metal cap flashing at the head was not sloped properly and the wood cap trim was not kerf cut. This caused water to pond (A), then run off the ends of metal flashing and behind the siding (B). The siding was scribed around decorative head trim and no thought was given to directing water outwards from the WRB, so it ran down the factory-applied pine trim (C), collecting at the sills. Roughly half of the home’s 30 windows exhibited the level of sill rot shown in photo (D). Note: the black Zip System tape shown here was used to temporarily seal window during construction.
Failing windows. To begin with, on the windows, the metal cap flashing at the head was not sloped properly and the wood cap trim was not kerf cut. This caused water to pond (A), then run off the ends of metal flashing and behind the siding (B). The siding was scribed around decorative head trim and no thought was given to directing water outwards from the WRB, so it ran down the factory-applied pine trim (C), collecting at the sills. Roughly half of the home’s 30 windows exhibited the level of sill rot shown in photo (D). Note: the black Zip System tape shown here was used to temporarily seal window during construction.


Portico problems. At the entry portico, kickout flashing had not been installed. Here, trim was placed over the step flashing, but no attempt was made to direct water running down the step flashing outward at the bottom (A)—water was allowed to flow behind the siding. This problematic detail also occurred in a couple of other locations, higher up on the roof. At the rake returns, the aluminum cap flashing sloped the wrong way, which caused water to pond against the trim and siding (B). The returns were probably built with too little slope to begin with, and over the years, settling caused them to reverse slope. Eventually, the silicone caulk sealing the aluminum cap flashing failed. When we started our repairs, we found the underlying rake-return boxes (C), adjacent trim, and framing had turned into compost (D).
Portico problems. At the entry portico, kickout flashing had not been installed. Here, trim was placed over the step flashing, but no attempt was made to direct water running down the step flashing outward at the bottom (A)—water was allowed to flow behind the siding. This problematic detail also occurred in a couple of other locations, higher up on the roof. At the rake returns, the aluminum cap flashing sloped the wrong way, which caused water to pond against the trim and siding (B). The returns were probably built with too little slope to begin with, and over the years, settling caused them to reverse slope. Eventually, the silicone caulk sealing the aluminum cap flashing failed. When we started our repairs, we found the underlying rake-return boxes (C), adjacent trim, and framing had turned into compost (D).


Mixing New Products With Time-Tested Methods


One facade at a time. In general, we replaced existing trim located closer to the ground, which was more prone to rotting; the home’s upper trim (the fascia, frieze, rake, and soffit) was in good shape. Working one facade at a time, we removed the existing siding and trim and replaced any rotted sheathing we came across. For the new weather-resistant barrier (WRB), we opted to use a drainable housewrap manufactured by Benjamin Obdyke called “HydroGap.” It comes with raised dots placed in serpentine pattern that provide a capillary break between the WRB and new siding, while also offering some ventilation. For the new siding, we installed HardiePlank lap siding, which we had pre-primed and painted. All the replacement trim was cellular PVC manufactured by Koma and the metal flashing was 16-ounce copper—we like copper because it’s long lasting and aesthetically pleasing and because you can solder the seam-work rather than relying on sealants to make watertight joints. Our painting subcontractor used Benjamin Moore Alkyd primer and Benjamin Moore Exterior for all the trim and siding finish.
One facade at a time. In general, we replaced existing trim located closer to the ground, which was more prone to rotting; the home’s upper trim (the fascia, frieze, rake, and soffit) was in good shape. Working one facade at a time, we removed the existing siding and trim and replaced any rotted sheathing we came across. For the new weather-resistant barrier (WRB), we opted to use a drainable housewrap manufactured by Benjamin Obdyke called “HydroGap.” It comes with raised dots placed in serpentine pattern that provide a capillary break between the WRB and new siding, while also offering some ventilation. For the new siding, we installed HardiePlank lap siding, which we had pre-primed and painted. All the replacement trim was cellular PVC manufactured by Koma and the metal flashing was 16-ounce copper—we like copper because it’s long lasting and aesthetically pleasing and because you can solder the seam-work rather than relying on sealants to make watertight joints. Our painting subcontractor used Benjamin Moore Alkyd primer and Benjamin Moore Exterior for all the trim and siding finish.


A better head detail. We joined the Koma head, jamb, and sill stock on the ground and fastened the resulting trim surrounds in place using the Cortex hidden fastening system (A). Out of Koma, we milled cap trim with a slope for drainage and a continuous kerf cut, and decorative molding. We fabricated the copper cap flashings on site with our Tapco Pro-III metal brake and metal cut-off wheel. After installing the PVC head cap trim, we slit the HydroGap WRB and slid the vertical leg of the cap flashing into the cut opening (B). To direct water outward from the head flashing, we slipped square copper flashing under the cap flashing on both sides of the head trim; the bottom of square flashing was lapped onto the fiber-cement siding. We fastened the cap flashing and square, lap flashing off with a four to five copper nails (C). The slit in the WRB was sealed with 3M all-weather flashing tape, which adhered to the raised, dimpled WRB without problems (D). Later on, the siding was butted to the head trim and then the decorative trim (with mitered returns glued up) was installed. This avoided the need to scribe the fiber-cement siding around a decorative molding, eliminating a potential water entry point, as was the case with previous head flashing.
A better head detail. We joined the Koma head, jamb, and sill stock on the ground and fastened the resulting trim surrounds in place using the Cortex hidden fastening system (A). Out of Koma, we milled cap trim with a slope for drainage and a continuous kerf cut, and decorative molding. We fabricated the copper cap flashings on site with our Tapco Pro-III metal brake and metal cut-off wheel. After installing the PVC head cap trim, we slit the HydroGap WRB and slid the vertical leg of the cap flashing into the cut opening (B). To direct water outward from the head flashing, we slipped square copper flashing under the cap flashing on both sides of the head trim; the bottom of square flashing was lapped onto the fiber-cement siding. We fastened the cap flashing and square, lap flashing off with a four to five copper nails (C). The slit in the WRB was sealed with 3M all-weather flashing tape, which adhered to the raised, dimpled WRB without problems (D). Later on, the siding was butted to the head trim and then the decorative trim (with mitered returns glued up) was installed. This avoided the need to scribe the fiber-cement siding around a decorative molding, eliminating a potential water entry point, as was the case with previous head flashing.


Rot-proof water table and chimney trim. In the rear of house, the existing water table trim transitioned into base trim, which butted stone pavers on a raised patio area. The existing rotted patio-to-wall base trim was too close to the ground and was not flashed properly. Here, we fit copper Z-flashing between the pavers and the rigid foundation insulation (A). Stone entry steps at the rear patio and front portico were rebuilt and pitched away from the house. The PVC corner boards were built to match the existing; the mitered drip cap was milled from Koma stock with a slope for drainage and a continuous kerf (B). For the water table, we purchased new Azek PVC drip cap; its trim profile was sloped for drainage and had a continuous kerf on the bottom edge. We fastened off the 12-inch-wide water table with Cortex screws and then installed the PVC drip cap with white aluminum L-flashing on top (lapped under the WRB) to prevent water from getting behind it. Here, the water table transitions to base trim the patio steps (C). For the stone chimney, we demoed the crumbling mortar joint and rubble backing and then slipped a wide piece of Koma trim into the resulting gap. Next, we finished the mortar joint to a continuous spacer placed over the Koma, which when removed, left a quarter-inch-wide gap to provide a flexible sealant joint (D).
Rot-proof water table and chimney trim. In the rear of house, the existing water table trim transitioned into base trim, which butted stone pavers on a raised patio area. The existing rotted patio-to-wall base trim was too close to the ground and was not flashed properly. Here, we fit copper Z-flashing between the pavers and the rigid foundation insulation (A). Stone entry steps at the rear patio and front portico were rebuilt and pitched away from the house. The PVC corner boards were built to match the existing; the mitered drip cap was milled from Koma stock with a slope for drainage and a continuous kerf (B). For the water table, we purchased new Azek PVC drip cap; its trim profile was sloped for drainage and had a continuous kerf on the bottom edge. We fastened off the 12-inch-wide water table with Cortex screws and then installed the PVC drip cap with white aluminum L-flashing on top (lapped under the WRB) to prevent water from getting behind it. Here, the water table transitions to base trim the patio steps (C). For the stone chimney, we demoed the crumbling mortar joint and rubble backing and then slipped a wide piece of Koma trim into the resulting gap. Next, we finished the mortar joint to a continuous spacer placed over the Koma, which when removed, left a quarter-inch-wide gap to provide a flexible sealant joint (D).


Restoring the covered entry. On the front-entry portico, we salvaged the existing roof framing, vaulted soffit, and four fiberglass columns, which we removed and stored on site. We replaced the roof’s built-up 2-by carrying beams and rake-return boxes (putting a decent slope on the top of the rake return) and then trimmed out the fascia, rakes, and rake returns with Koma (A). The rake-return cap flashing was made with three pieces of copper, its seams soldered to act as one piece (B). We re-shingled the roof and, for aesthetic reasons, we doubled up on the new kickout flashing. The larger, upper kickout sheds most of the water, allowing the lower one to be more subdued (C). Finishing up, the fiberglass columns were re-installed, new fiber-cement clapboards were installed on the front façade, and the trim work was primed and painted (D).
Restoring the covered entry. On the front-entry portico, we salvaged the existing roof framing, vaulted soffit, and four fiberglass columns, which we removed and stored on site. We replaced the roof’s built-up 2-by carrying beams and rake-return boxes (putting a decent slope on the top of the rake return) and then trimmed out the fascia, rakes, and rake returns with Koma (A). The rake-return cap flashing was made with three pieces of copper, its seams soldered to act as one piece (B). We re-shingled the roof and, for aesthetic reasons, we doubled up on the new kickout flashing. The larger, upper kickout sheds most of the water, allowing the lower one to be more subdued (C). Finishing up, the fiberglass columns were re-installed, new fiber-cement clapboards were installed on the front façade, and the trim work was primed and painted (D).


Elliptical flashing; new siding and gutters. There were a few instances where we had to flash above elliptical-shaped head trim. Rather than cobbling together the flashing with a series of stepped pieces to make a curve, as shown here (A), we fabricated one-piece head flashing in our shop. We shaped the three-directional head profile with shrinker and stretcher metal fabricators from Eastwood. Next, we, installed the elliptical flashing similar to the standard head flashing, lapping the ends onto the fiber-cement siding to direct water outward from the WRB (B). For the siding, we field-tested the new dustless siding shear from Bullet Tool to cut the HardiePlank (C). The cutter has a super stiff, sharp blade mounted beneath a lever that shears the material when pressure is applied on the lever. The resulting cut is crisp and smooth, and this method allows the user to skim material off in very small increments. For the replacement gutters, we chose fiberglass ones, manufactured by the Fiberglass Gutter Company. The gutters have been molded from actual cedar and fir wood gutters, which transfer the wood grain look and texture. We visited their factory in Pembroke, MA a few months ago for a demonstration (my crew will be assembling the gutters on site). The gutters are surprisingly strong, given their thin profile (D). The seams connecting long runs and mitered corners are joined with site-mixed resins and fiberglass reinforcing mesh. We’re installing the gutters in the near future and plan to use appropriate respirators while doing the seam work.
Elliptical flashing; new siding and gutters. There were a few instances where we had to flash above elliptical-shaped head trim. Rather than cobbling together the flashing with a series of stepped pieces to make a curve, as shown here (A), we fabricated one-piece head flashing in our shop. We shaped the three-directional head profile with shrinker and stretcher metal fabricators from Eastwood. Next, we, installed the elliptical flashing similar to the standard head flashing, lapping the ends onto the fiber-cement siding to direct water outward from the WRB (B). For the siding, we field-tested the new dustless siding shear from Bullet Tool to cut the HardiePlank (C). The cutter has a super stiff, sharp blade mounted beneath a lever that shears the material when pressure is applied on the lever. The resulting cut is crisp and smooth, and this method allows the user to skim material off in very small increments. For the replacement gutters, we chose fiberglass ones, manufactured by the Fiberglass Gutter Company. The gutters have been molded from actual cedar and fir wood gutters, which transfer the wood grain look and texture. We visited their factory in Pembroke, MA a few months ago for a demonstration (my crew will be assembling the gutters on site). The gutters are surprisingly strong, given their thin profile (D). The seams connecting long runs and mitered corners are joined with site-mixed resins and fiberglass reinforcing mesh. We’re installing the gutters in the near future and plan to use appropriate respirators while doing the seam work.


Completed restoration. In the end, our clients were pleased with the restoration. All told, replacing the home’s trim, siding, and windows took about 950 man-hours to complete. One wonders how many more years the homeowners would’ve got out of their exterior cladding had the existing trim and siding been properly primed and flashed—not to mention the direct correlation to poor window head flashing and damage to about half of the home’s windows.
Completed restoration. In the end, our clients were pleased with the restoration. All told, replacing the home’s trim, siding, and windows took about 950 man-hours to complete. One wonders how many more years the homeowners would’ve got out of their exterior cladding had the existing trim and siding been properly primed and flashed—not to mention the direct correlation to poor window head flashing and damage to about half of the home’s windows.