When roofing has to be done in stages, for instance on multi-family structures such as townhouses or duplexes, tying the new shingles into an adjoining, existing roof can be a challenge.

Atlas Roofing recommends shingling the entire roofing plane, if possible, to maintain what it is known as “the watertight integrity of the adjoining roofs.”

In situations where re-shingling the entire plane is not possible – for instance, if the age, condition or color of the existing roof is different from the new shingles – Atlas offers the following installation guidelines:

• Install an area divider between the section being re-roofed and the existing roof area, which creates a stopping point and a clear separation between the two roofs.
• Flash the new section in accordance with Atlas application instructions and follow guidelines and best practices outlined by the Asphalt Roofing Manufacturers Association (ARMA). The remaining roof will need to have new step flashing installed as well.
• Finish the area divider with metal coping that can be removed if the other section of roof needs to be replaced in the future.
• Do not cover the open seam between the connected roof areas with ridge cap shingles. Water moving laterally under the ridge caps can cause leaks if it reaches the vertical seam.
• Do not weave shingles at the tie-in area.
• As always, follow all local building codes.

Atlas Roofing’s Limited Warranty on roofing shingles is intended to cover manufacturing defects and is valid within the terms and conditions stated in the written warranty document.

For coverage details, refer to the Atlas Limited Warranty page on the Atlas website.