CDH said:
Thanks for your input. I'm sure that what you're saying is correct and I will be taking your advice to have an experienced installer look at the site to determine the best course of action.
However, the DNSC installer had many more issues than simply following a no-chimney policy. He had never seen a 942, had no idea about the TV2 output, had no idea how to integrate an OTA antenna, etc. He wanted to slap two roof-mounts into the plywood of my roof with the silicon gel mentioned above. He was very clear that he and his company would take no responsibility if the install was botched and caused leaking into the roof.
Also, as I'll be resurfacing my roof in the next couple of years I didn't want to have to remove and then reinstall dish mounts.
CDH.
Being in the came geographical area as you are, I know the subcontracted install outfit that you had to deal with. They are not DNSC, but a large contractor for installs. In your case, I would have not recommended that such installers mount on the roof either. I have a degree in structual and mechanical engineering and 35 years of experience with house and building structures. I am a master electrician and have been involved with OTA antennas since the
Golden Age of Television ,when everything was OTA. Silicone sealant is not a good sealing method for asphalt based fiberglass matted roofing material.
THis is a correct roof install method;
DBS ROOF INSTALL TECHNIQUE
I install a lot of roof mounts on pitched asphalt shingle roofs. I never never use silicone or roofing cement or coatings. And, I never use those lag screws that require predrilling.
I use #14(1/4"dia) fully threaded hardened hex head drive sheet metal screws. I drive two three inch long ones into the rafters and four 1-1/2" long ones into the corners of the feet. It is not difficult to find the rafters, since hitting the roof surface with the back of your fist will result in a solid sound. Even if you miss, six fully threaded screws will provide a very good hold that will require a hurricane or a tornado to blow off. In that case, the home owner's insurance will apply, since it will be considered an "Act of God."
The above provides for one solid mount. The screws driven through the shingles, without predrilling, provides a near perfect seal, since the heat generated in driving them melts the asphalt, which rehardens around the screw. This is also basically how roofing nails work. Just for insurance and for those customers who inspect the install, I cover the heads with a pliable modeling clay like duct seal. A one pound brick costs no more that $2 at Home Depot. This is also perfect for sealing cable wall entries.
The best level that I have used is the Israeli made Post-Rite sold at Sears for $5.99. It is a post level with two bubbles spaced 90 degrees apart on a vertical hinge. The magnets don't work that well, but the elastic strap holds it firmly on the "J" pole. It's worth having, if you do a lot of installs. Forget the bubble level that fits on the inside of the mast. It requires you to get up and increase your center of gravity to look at it from the top, which can be dangerous on a steeply pitched roof. With the Post-Rite, you can do everything while sitting on the roof's surface and still have access to see the levels, without moving your position above and back down to the mounting.
The center of the dish mounting foot is usually marked with an embossed line down the center. Except for a very old mounting foot, one of the center holes is round, and the other is a slotted arc. The first step is to screw in the long 2-1/2" to 3" long screw into the round hole, just driven down enough so that you can pivot the foot on this one screw. Swing the pole up and down and pivot the foot until both bubbles on the Post-Rite are centered. Drive in the second lomg screw. Then, drive in the short corner screws until snug. Using the bolts and nuts that hold the pole to the foot, tighten them for a final adjustment, if plumb had shifted a little due to the roof shingles having been compressed from driving in the screws. Use small balls of duct seal the size of a small marble and work them over the screw heads.
Set the skew or tilt and elevation correctly on the dish correctly for the locality. Place the dish back on the pole and tighten the vertical clamp bolts just tight enough to take up all of the wobble. Swing the dish horizontally until you get the highest signal levelon the meter. Tighten the vertical sleeve mounting bolts. Check the TV to verify signals for each satellite position.
Removal of Dish Mount
Backing out the screws leaves holes of less that 1/4" that are almost undetectable to the casual observer on the ground. The mounting foot is not "glued" to the shingles and comes off without tearing them. Whoever thought gluing the mounting foot to the shingles provides security is a fool. If the wind blows the dish off in a hurricane, a lot of shingles comes off. If held only with screws, a dish blown off results in less damage. The duct seal is great for sealing the holes left from the removed screws. Filled holes can be very discrete.
If you are removing a previously "glued" mounting foot, the way to do this with the least damage is with a thin stainless steel wire, such as aircraft safety wire or a piece of piano wire wrapped between two sticks like a garotte. Saw away the silicone with the wire, and the mounting foot comes off pretty clean. I're even used this method to take off mirror tiles stuck to dry wall, without damaging the surface.
If you are replacing shingles, the dry wall knife is your best friend. It allows you to lift the heat activated glue down tabs of asphalt shingles without breaking them off.