Flat Roof Analysis

Some good info from Maggio Roofing:

Flat Roof Analysis

Almost all flat roofs in Washington DC are constructed with main support beams (2x10's) that are pocketed into the side brick walls. On top of these walls sit rafters (2x6's) that are fastened to these main support beams. Then, there is wood sheathing (1x6's) that are fastened into the rafters. The roofing materials are then installed over top of the sheathing.

Current building code requires that this roof structure be able to hold a live load (LL) of 30 lbs per sq foot, a dead load (DL) of 15lbs per sq foot with a total load (TL) equal to 45 lbs per sq foot. The issue at hand is that almost all of these flat roofs have the rafters spaced at more than 24" apart. This means that the code will require this roof structure assembly to hold 90lbs per sq foot. The problem is that this assembly will only have an allowable load of 60lbs per sq ft. What does this all mean? It means that your roof structure does not have the structural support to handle the necessary loads that current building codes calls for. Even though structural engineering requirements are conservative, there is a risk here. In January 1922 the roof of the Knickerbocker Theater in Mt. Pleasant, collapsed under snow from the storm subsequently named for this same collapse. January 14, 1996, during the "storm of the century", Potomac Mills Mall was evacuated due to snow causing metal beams to sag in two places, which caused the ceiling to droop about three feet. Inspectors declared the mall unsafe at that time. These stories have a tendency to be forgotten.

During the year, we find that 10-15% of the new roofs we install, require structural work due to sagging, cracked, or broken main support beams. Another 10-20% require rafter repairs due to sagging or rotting conditions. Many homeowners are quick to say, "my house has been here for 80 years and hasn't collapsed, why would it now?" My answer to that is, "What is your life worth? Do you really want to take that risk?" This risk gets worse when negligent contractors start installing heavy solar panels or other roof top equipment without taking the structural loads into account.

In order to meet code, the structure would need to be composed of 2x8's 24" on center or 2x6's closer together (less than 16" on center). So, in order to install solar panels on roofs (since roofs in your neighborhood are composed of 2x6's) you will need to modify the structure to support the new loads on the roof.

If contractors are not getting in the attics and looking at the rafters, then they are putting residents at extreme risk. If they are looking and tell you that its OK, they are either not being truthful or they just don't know the facts. Don't let anyone install any solar panels or other heavy equipment on your roof without having the structure visually seen. This may not be possible most times due to access. In those situations, it is better to assume that the structure is not built to support the load and will need modification.

This means that the only way to install solar correctly (and not put residents at risk) is to install one of the following methods:

1. Remove the roof and install additional main beams (either sister laminated beams or install new)
2. Install new 2x6 rafters sistered to the existing or new 2x8 rafters.
3. Install new sheathing.

OR

1. Install steel I beams that rest on the parapet walls
2. Install solar panels on racking that are attached to I beams

OR

1. Install thin film solar system.

http://www.maggioroofing.com/services/roof-analysis/

11 Kw Home System

President Solar hopes to find its place in the sun

By Thomas Heath
Monday, April 26, 2010; 2

I caught up with Roy Dunbar on the telephone as he was fending off hungry herons trying to poach at his koi pond outside his McLean home.

The former chief executive at Herndon-based Network Solutions has launched a new business called President Solar, which will distribute rooftop photovoltaic (PV) solar panels to solar companies that install the panels for residential and small commercial customers.

Dunbar has invested $500,000 already, and probably will invest another $500,000 in the near future. And he wants to make money.

"I have actually been involved and interested in solar for quite some time," said Dunbar, 49, who left Network Solutions last fall. "On the roof of my house is an 11-kilowatt system."

Although the systems can cost thousands to install, Dunbar said federal, state and even local tax breaks and rebates could induce residents and businesses to take the plunge. Solar customers also can sell solar renewable energy certificates to utilities and others on a secondary market.

He has an office and warehouse in Fairfax County and three employees. He is buying the panels in volume from a supplier in Eugene, Ore., called Grape Solar.

"What we are doing is distribution," he said. "But with this market getting so hot . . . I am toying with the idea of setting up an assembly plant," which would manufacture the panels.

The market wasn't hot enough for BP Solar, a unit of the British oil giant that last month announced plans to stop assembly at its Frederick plant because of a big drop in prices for solar systems.

"I know it flies in the face with what just happened to BP Solar, but you might be able to put [a factory] together that makes 60 or 70 jobs on a local scale," Dunbar said.

PVs contain a solar photovoltaic material that converts solar radiation directly into electric current. Dunbar said the solar panels on his roof had stored enough electricity in batteries to keep his home's critical systems running for more than four days during February's "Snowmaggedon."

http://www.washingtonpost.com/wp-dyn/content/article/2010/04/23/AR2010042303966.html

Latex Paint Disposal

The DC Department of Public Works web site seems to be of two minds about latex paint (and it's can). First latex paint is listed as "Unacceptable household hazardous waste" and then under a section called "How You Can Help" we are told that latex paint is "not hazardous".

"Unacceptable household hazardous waste and e-cycling items include:

• Air conditioners (Call 311 for a bulk trash collection appointment.)
• Ammunition (Take to the closest police station.)
• Explosives (Take to the closest police station.)
• Latex paint (Dry out and place in the trash.)

How You Can Help

Latex paint is NOT HAZARDOUS. If you have unused latex paint, remove the lid and let it dry out. Then place the can in the trash. You can speed up the drying process by adding some kitty litter to the paint."


Not sure I want to cut through the semantic acrobats of the logic that allows both of those assertions to be true nor do I want to push the limits of recycling possibilities - I just want to get rid of the stuff in as safe a manner as I can given the circumstances...... and it is clear DPW wants me to dry the paint out and put it in the trash.....

So I dried out the paint and left the paint can in the trash container a couple of weeks ago. After the garbage crew came through, I found the paint can left behind next to the garbage can. Other garbage was gone but not the paint can. Hmmmmmm. Will try again.