Roofing/roofing problem


How to fix a dead mans valley on a 3year old house.
Four slopes of the roof come together at one point for about four to six feet. What can be used to seal this area?

Just to be clear about our terms, a "dead or deadman's valley" is where the downhill edge of a roof section joins the downhill edge of an opposing roof section(s) so that the valley created is virtually flat.  Water flowing down those sections will end up at the bottom of this valley and have to flow sideways to exit the valley.

In the past on residential homes they may have used 90 pound roll roofing. On a three year old home the builder may have used and eave protection membrane under a metal valley, you did not say what was there.

Today we have SBS modified membranes. These membranes come in a metre wide roll and can vary from 8-15 metres long. The base sheet membrane is smooth om top whereas the cap sheet membrane has the granular finish of a shingle.

I would suggest a two-ply modified membrane, base and a cap.

The base sheet can be installed either fully adhered (a self-adhesive base sheet is available) or laid loose and nailed in the laps before sealing and in the body of the sheet.

The cap sheet membrane can either be torch-applied, cold applied with adhesives or self-adhered.The base sheet would have a plastic film on top (self-adhesive or torch on cap) or a sanded finish for cold applied with adhesives.

Depending on the products used the base sheet can be 10-15 metres long and the cap sheet 8-metres long. The product will be reinforced with polyester fabric.

Consult a local roofing material supplier for info on products from companies such as Soprema, IKO, Bakor.

The shingles will have to be removed in the valley so the membrane can be terminated at least one foot up and under the shingles before they are re-installed. Check the manufacturer's detail on their websites.

If you need more info please feel free to contact me.
a fellow Canadian.


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D. John Henderson


My 33 years in the building science business has involved air barriers, waterproofing, and flat & steep slope roofing systems.


My roofing encompasses commercial systems (BUR, mod-bit, single-ply) and residential applications (asphalt shingles, cedar shingles, slate and metal. I am cognizant of code stipulations in regards to FM and UL for commercial roofs.

Attended numerous courses offerd by Roof Consultants Institute, Roofing Industry Educational Institute, Factory Mutual Research Corporation, University of Wisconsin, and BURSI. Lectured for RCI and mentored at a local university for a Building Science Certificate.

Past/Present Clients
Government, commercial businesses such as The GAP, hospitals, school boards as a roof designer.

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