Find the right caulk for your home project | Consumer Reports
  • Latex - Inexpensive - can be sanded and painted - won't adhere to metal Will crack eventually where temperatures vary greatly
  • Acrylic latex formulations are more durable.
    It is water-based, so shrinks at it cures.
  • Butyl rubber - More flexible than silicone - can be painted after 1 week
  • Siliconized latex - very durable and flexible - can't be sanded
  • 100% Silicone - Very durable - can't be painted or sanded
Most caulks are composed of latex, acrylic latex, silicone or polyurethane.
Latex is easier to apply. Can work on porous and nonporous surfaces
Acrylic Latex is more durable
Silicone is more difficult to apply, best on nonporous surfaces and only some are paintable.
  It is more flexible and lasts longer. See below.
Polyurethane is difficult to work with, but better for concrete because it adheres well to porous surfaces.
Many companies now make caulks that are combinations of latex and silicone. They are often marketed as "siliconized latex" or "latex plus silicone." These products offer the ease of use of latex with the added durability of silicone.
But they can't be sanded.
In 2007 PaintPRO said "Paintable silicones have proven to be far from perfect"

Commercial Grade:
I noticed the stuff my roofers used was better than the stuff I got at HomeDepot.

I went to my local Allied Building Products (recommended by a contractor/engineer friend).
The recommended NPC Solar Seal #900 ($7.40 per tube). A premium adhesive/sealant based on terpolymer technology which offers an alternative to silicone & urethane sealants and caulk.
Technical Data Sheet
Ingredients: Resin, Rubber Elastomer mixture (proprietary); Petroleum Solvent; Titanium Dioxide; Calcium Carbonate
Standards: ASTM C-920, Type S, Grade NS, Class 25, TT-S-00230c, Class A, Type II

NPC Solar Seal 900 Adhesive Sealant: Industrial & Scientific

My local lumber store (Somerville Lumber) recommended Sashco Through the Roof ($8)
Super elastic, Lasts 20x longer than asphalt.
Standards: ASTM C794

The following are some rules of thumb for specifying roofing sealants:

On asphalt: use an asphalt caulk.

On modified bitumen (asphalt and a variety of rubber modifiers and solvents.): use a modified bitumen mastic. In critical areas where movement is anticipated, use a good grade of urethane or polyether sealant.

On EPDM ((ethylene propylene diene terpolymer) - synthetic rubber: use a solvent-based EPDM lap seal caulk on splice joints. On flashing: use polyether sealants. Urethane sealants usually don't adhere to EPDM.

On PVC: use a polyether sealant, urethane or an oxime-cure silicone.

On Hypalon (less than six months old): use only fresh Hypalon sealant. On weathered Hypalon: don't attempt to use a sealant; it will probably fail.

On TPO (Thermoplastic polyolefin): use a urethane or polyether only with an effective primer. Carlisle and Chem Link have an effective TPO primer.

On polyurethane foam: use urethane, oxime-cure silicone or polyether sealants.

On most metal roofs: urethane or oxime-cure silicone (non-corrosive) and polyether sealants work well.

On Kynar (polyvinylidine flouride)-coated metal: oxime-cure silicone works well. Urethane does not bond at all to Kynar.

Avoid using caulk on all single-ply membranes.

Source: From Caulk to Sealants |

Chimney repair:
Repair Cracked Chimney Crown - Add Top Sheet Metal Flashing Cap - Flue Guru - YouTube
Find the right caulk for your home project | Consumer Reports
Caulk Buying Guide Lowes
Best Exterior Caulk? - Painting & Finish Work - Contractor Talk
Exterior Caulkling - PaintPRO Magazine
From Caulk to Sealants |
Caulking - Wikipedia, the free encyclopedia

last updated 22 Mar 2016