Flashing Roof Repair

by Fred on November 2, 2012

flashing roof repair

Using Lead Flashing And Lead T-caps For The Weather Proofing Of Building Roofs, Chimneys And Walls

Lead strips are often used in construction to provide a weather proof barrier and sealer, particularly, in historic building restoration. Examples included Lead flashing for roofing systems, where a masonry chimney connects to the house and a leak proof roof penetrations. Lead T-caps are used to bridge and seal gaps in masonry walls.

The properties of lead make it ideal for this kind of application, Lead is malleable so it will easily conform to the roof contours and lead will also stand up to inclement weather particularly observed in the North Eastern United States.
This article describes the varies uses for lead flashing, lead t-caps and other lead products used in the weather proofing of roofs, chimneys and walls.
Lead Roof Flashing
Lead flashing is used in roofing systems to eliminate leaks at intersections and roof edges. The most common locations for lead roof flashing include Roof joints, valley flashing, chimney flashing, and roof penetrations such as lead roof jacks.
Lead flashing materials are popular particularly in northern climes as they are soft and easy to bend to shape, durable and weather resistant. Lead flashing is also able to accommodate movement between adjoining components.
Lead Chimney Flashing
Lead chimney flashing easily accommodates any movement caused by the settling of the chimney foundation which is often separate from the main house foundation.

The correct use of lead flashing around chimneys includes two layers. The first called step flashing, involves sections of L-shaped lead roof flashing which are lapped up the side of the chimney. Secondly, lead counter flashing is folded down to cover the top of the lead step flashing.

Repairing Lead Flashing on a Roof
Lead flashing can last up to 500 years, however proper installation requires some experience and skill. Damaged lead roof flashing should be replaced as soon as practical. Lead flashing where shingles meet a wall or other vertical surface may be patched. However, it’s not practical to repair lead flashing in the valley where two roof planes intersect; in this case new lead flashing must be installed.
On older houses the flashing is a common point of water entry, even though lead flashing can last for centuries eventually it will need to be repaired or replaced.
The most common locations for roof flashing are at valleys, chimneys, roof penetrations, eaves, rakes, skylights, ridges, and at roof-to-wall intersections.
Lead flashing usually comes in the form of lead rolls consisting of flexible lead sheets.
If the lead flashing was installed when the house was built it is likely embedded in mortar, if it was added later the flashing may be in the form of a lead strip attached across the joint using waterproof adhesive.
Minor repairs can be performed with the lead flashing still in place. Small cracks can be repaired using bituminous sealer, and small holes or small areas of light corrosion can be repaired using metal backed flashing strip.
Over time the mortar is likely to become cracked and to flake away, this will have to be repair to maintain a water tight seal. In this case the lead flashing will have to be removed or moved aside so that the mortar can be repaired or replaced. Rack back about a dozen millimeters of mortar to get a good fixing point for the lead flashing and then feed the flashing back into its slot and re-point with new mortar
If the lead flashing is substantially corroded it will have to be replaced. Chip out the old mortar with a hammer and chisel, clean out the gap using a wire brush and repoint with new mortar. The new flashing will not be embedded in the mortar so it should be allowed to dry. Apply flashing primer to the joint and apply two new strips of metal backed self-adhesive flashing, one slightly offset above the other. Finally, coat or paint the flashing as desired.
Care must be taken when dealing with corners, for internal corners cut into the lower edge of the lead flashing, overlap the edges and smooth. External corners require that an additional square patch of flashing be attached around the corner prior to attaching the main strip. As with an internal corner cut part way through the bottom edge of the strip where it passes around the corner and smooth down.
Lead t-caps
Building movement or settlement with resultant joint checking can result in leakage and moisture penetration. When the movement is significant caulk or sealant will not be sufficient to create a weather tight seal.
T-Caps installed in caulked joints will reduce the size of the opening of a joint to be caulked to assure improved, long lasting leak free joints. The proper sized T-Cap is determined by measurement of the joint opening to be caulked plus maximum percentage of joint movement experienced plus 1/4 inch.
T-Caps are a soft lead strip which when set and bedded in caulking compound, forms a cap which assures a permanent elastic seal for any masonry joint. After installation, the surface oxidizes rapidly to a neutral grey which blends with the masonry.
T-cap Locations
1.Top, side and cross joints of copings and balustrades. Extend from outer face, across the top of the coping and down parapet side.
2.All cross joints on cornices and belt courses. Carry down at least 1 inch on front face of stone, or down front face of stone to first change in contour as desired.
3.All cross top joints on window and door lintels, entrance porticos, brackets, pilasters, water tables and any other piece of masonry which projects beyond the face of the building.
4.The joint at the top of all projecting window or door lintels, entrance porticos, brackets, pilasters and any other masonry projections where those units join side wall or parapet at approximately right angles.
5.All joints between sill of window frame and masonry supporting sill.
6.All joints around plain or ornamental window and door frames
7.All right angle joints on building entrance steps where the treads and risers meet, and where treads and risers join stringers.
8.All joints around perimeter of glass block windows or panels.
9.The Flat Cap – for Use in joints between units set in the same plane. It is made in sizes as shown below.
T-Caps typically come in sizes ranging from 9/16 to 2
Other applications for Lead in construction
Custom Lead Gutter Outlets and Lead Goosenecks – Standard outlets, range from 1.25 to 2.00 in diameter. diameter x 5.5″ length
China Cap Vent – Used for exhausting inside air, bathroom fans, kitchen stoves and heated exhausts where code allows.
Dormer Vents – Used for attic ventilation

About the Author:
Nuclead offers lead shielding & lead flashing, lead bricks & sheets, lead based alloys, lead bar stock, lead bullets & extrusions, lead weights, ingots & other lead products.

Source: http://www.articlesnatch.com/Article/Using-Lead-Flashing-And-Lead-T-caps-For-The-Weather-Proofing-Of-Building-Roofs–Chimneys-And-Walls/3917146

Frequently Asked Questions

  1. QUESTION:
    Is there a way to repair flashing around chimney (or a few shingles) without going on top of the roof?
    I want to see whether we can open a small hole from the roof (under the roof) to repair the flashing or a few shingles without going on top of the roof. It is because the roof is high and it is not safe to do it yourself I think. Your feedback and experience will be greatly appreciated! Thank you!

    • ANSWER:
      use scaffolding and roof jacks to make a safe work platform…you could fix the flashing from a hole in the roof but then you have to fix the hole…so just do the flashing from the roof…

  2. QUESTION:
    how do i repair lead flashing around stench pipe on roof?
    There is a stench pipe sticking out of the roof of my house. The lead flashing around it is coming away. How do I repair it?

    • ANSWER:
      Clean it well, but don’t use an abrasive. Layer roofing cement or torch-down material over the lead to seal it.

  3. QUESTION:
    Roof repair-Replacing lead flashing (valley) on a pitched roof.?
    Hi, i’m looking to replace the lead lining (code 4/code 5) on a semi-detached roof. I’ve searched the internet and i’ve come across a ubiflex product which is a lead alternative and its self adhesive . Will this product be good enough for roof valley flashing and if so whats the procedure for the installation. Thanks

    • ANSWER:
      Usually it is the middle of the lead that is white and oxidised.Instead of replacing it,I have found that coating the whole area in ACRYPOL is best solution.Look up on google for instructions

  4. QUESTION:
    Would like to know if a repair collar is available for a vent pipe roof flashing?
    My vent pipe flashings are leaking due to cracking of the rubber donut which slips over the pvc vent pipe. The metal flashings are fine, only a couple years old, but the rubber is badly deteriorated. A web search mentioned that a repair collar is made to slip over the vent pipe so that you do not have to tear up the shingles to replace the entire metal unit. I have checked with plumbing supply houses but no one has heard of it. Does anyone know the manufacturers name of this repair collar or where I could buy it.

    • ANSWER:
      Buy a new aluminum vent cap at your local home center. Cut off the square part so it is round. Put flashing caulk on the old riser part of the flashing and slide the new one over the whole thing. Use tin sheers and cut about 1/2 inch off the bottom of the new riser. The flashing caulk will hold the new riser down .

  5. QUESTION:
    Rust under flashing on metal roof.Repair?
    I have some rust and corrosion under metal flashings on a roof. If I exclude moisture (apart from that in the air) by placing another flashing over the top will this stop the rust continuing? It would be easier than removing the existing flashing.Thank you. Neil

    • ANSWER:
      putting something over it will not stop the rust.


Flat Roof Flashing Repair, Tile Roof Flashing Repair, DIY Flashing, Flashing Leak, How to Roof Flashing, How to Fix Roof Flashing, How to Install Roof Flashing, Roof Flashing Repair Cost,

flashing roof repair

Fred (380 Posts)


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