12:07 PM 08/14/2012
I have an typical interior row-house in Petworth, and my porch looks original--concrete, perhaps reinforced with rebar sloped slightly toward the street to drain water. Nearer the street, the porch is supported by a low brick wall about 8 inches thick that runs the length of the porch parallel to the house. At the house, the porch seems to be supported underneath by a protruding ledge of brick, and may, in fact, actually connect to the house. It's hard to tell, but that ledge of brick seems to be in pretty bad shape. The porch is not supported on the sides
Here's my problem: About a month ago I installed rain barrels, 2 in the back, 1 in the front. But as I was about to hook up the one in front--which happens to be on the porch itself--it occured to me that maybe the porch couldn't handle the weight. We're talking about 500 or so pounds of water when full. So, to the Petworth community... Should I be concerned? As I said that ledge of brick underneath does seem to be in pretty bad shape, but I honestly don't know how this porch is *really* supported. Or, perhaps 500 extra pounds is inconsequential compared to the weight of the slab.
Thanks for any advice.
Concrete has enormous strength in compression, but is relative weak in expansion. The rebar in the concrete helps absorb some of the expansion force from deflection of the slab, and taller structures in DC use post-tensioned steel cables through the slab to reduce net expansion forces. So keeping in mind that the mass of the porch is probably greater than the mass of the rain barrels, as long as the load of the porch is bearing directly on something (say, a well-mortared brick ledge) and not toward the middle of the slab you should be alright. (Disclosure: Lector emptor - reader beware)
2:42 PM 08/15/2012 | 0 Votes
If you pass on the address, I'll stop by and take a look. Desvcrptions may be accurate but it is field conditions that provide the answers...retired building inpector in DC
7:20 AM 08/16/2012 | 0 Votes