Brand New Porch Roof is Leaking in Seam Between Soffits and New Porch Roof. What is Needed to Fix It; Cost?

Updated November 24, 2020
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Question by Rtg205: Brand new porch roof is leaking in seam between soffits and new porch roof. Contractor came out 2xs to "fix" the issue and re-caulked the seems, it's still leaking. Appears to have tape like material over seams, that has been caulked over 2x's now and continues to leak.What will be needed to fix the issue, and how much will it cost?

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Answered by LCD: In my response I am going to assume house and porch roof both slope same way, though maybe at different slopes. If they slope opposite directions (downwards towards each other) or in perpendicular directions (typically at 90 degree angle with each other, as with a peaked or gabled porch roof intersecting the house roof plane) then that interface should be treated as a roof valley, with ice and water shield and water barrier under metal flashing under the roofing material (maybe with exposed metal flashing in center).

Generally, caulking is not a permanent roof fix for more than leaking nail holes or such - and certainly not with a new roof. The "tape like material" you mention is likely ice and water shield (sticky-backed bitumastic/asphaltic roll-out waterproofing) - which should not be permanently exposed to the weather and rain - it is a backup protection against backup of water or leakage through the primary roofing material.

Assuming this is a situation with a porch roof abutting the fascia of the house roof, unless the elevation drop is enough for the house roof to have gutters above the porch roof, or the porch roof is built with a horizontal clearance gap between it and the fascia, this requires ice and water shield running off the house roof (generally should run up under the singles 3-9 feet depending on your icing/snow damming conditions and roof slope), and running continuous down over the joint between the two roofs and onto the porch roof. Detail depends on specific circumstances - but the key is getting the roof runoff (including any leaking water running off the house roof water barrier and/or ice and water shield under the roofing itself) to drop onto the porch roof if they are not continuous and are abutting with an elevation change. Or if continous from house to patio roof without an elevation drop at the interface (though there may be a slope change) to have continuous roofing and water barrier from house onto the patio roof without a "joint" at all. The latter where the porch roof is tight against the house roof fascia or is built continuous with the house roof rafters with the roofing surface continuing onto the porch roof.

Cost - to do it right probably about $2000-3000 assuming about an assumed 40 foot or so contact length - though since this is a new roof that should come out of the contractor's pocket, or if he is unable or unwilling to fix it right, paid by his Bonding company for another roofer to do it right. Will generally require removing about a 4-8 foot wide strip of roofing straddling the interface line and some opening up of the water barrier (roof wrap) along the interface line to make it right - towards the lower width if there is a vertical offset or steep (4:12 or steeper) roof, wider for continuous transition or for flatter roof or heavy ice damming risk area, because assuming the porch roof is unheated in winter that interface becomes a natural ice damming formation point.

If the porch roof connects in at the house roof fascia rather than extending each rafter out over the porch, that vertical transition area should be ice and water shielded as well to keep water out of the fascia/soffits. If a vertical offset exists, fascia should be ice and water shielded, ideally be metal clad as well, and the house roof should have substantial metal dripedge flashing to divert its runoff onto the surface of the porch roof.

Of course, details will vary depending on the exact configuration at the interface, but the key is when tracing water downhill on any surface (roofing, water barrier, ice and water shield) that water should continue on the same surface (if continuous porch to house roof) or if there is a vertical difference in roof elevations at the interface, be deliberately and in a controlled manner ejected from the house roof onto the surface of the porch roof with proper roofing and ice and water shield overhang and underlying drip edge.

Here is an article with illustrations showing the transition for a continuous roof with slope change - higher quality roofing jobs will use metal strip flashing under the transition as well as ice and water shield, though not required by all building codes.

For a roof with a dropoff from the house roof to the porch roof but abutted tight against the fascia on the house roof rafters, the fascia should be fully top and front-face waterproofed with ice and water shield and/or metal flashing because if it ever rots out you have a horrendous job replacing it. The rest of the detail would be similar to a porch roof abutting a vertical house wall - with ice and water shield and flashing running continuous from the house roof down over the fascia and then onto porch roof (ice and water shield onto top of porch roof ice and water shield, flashing onto top of porch roofing) to protect against splash, with dripedge intercepting and dropping the house roof water out onto the surface of the porch roof- preferably well out beyond the interface by tucking the porch roof in under the overhanging rafter tails to provide a foot or two house roof overhang over the back edge of the porch roof.

If the porch roof is flat ideally an air gap would be kept between house roof fascia and porch roof (so independently support porch roof on all edges) so any backup does not back up into the house fascia and roof. If that is not possible than a sloping transition is recommended to keep any ponding from backing up against the house structure - keeping any ponding at least 6 inches and hopefully a foot or more out in front of the house roof fascia and rafter tails.

If an elevation difference exists but is less than about three feet, then the ends of the house roof rafter tails need to be fully protected against splashing on the porch roof from saturating the edge of the house roof framing. A fully metal clad fascia board covering the rafter tails is commonly the easiest way to do this.

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