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Weekly Engineer’s Jargon

rebarRebar (reinforcing bar) is used to reinforce concrete structures. A stick of rebar is categorized by a number (i.e. #4). The number represents the number of 1/8ths inches in diameter of the bar. For example, #4 Rebar is 4/8” or 1/2” in diameter, #3=3/8”, #8=8/8” or 1” and so on… The largest I’ve specified was a #11 bar for a building at Glenridge in Atlanta. That’s heavy duty reinforcing!


Picture Of The Week

pow
That’s what I call a leaky foundation!



Question #3 from Ms. A.: 
We bought a home and have noticed that the floors are not leveled. Our chairs with wheels roll down hill as your sitting in them. We went under the house and found that there are no cement blocks holding up the house. All we saw were 4×6’s. The roof is sagging and uneven as well. Would it be possible to level out the house and put down a sturdy foundation? The home was supposedly updated in 2005. 


Answer from Chris: 
Ms. A., 
Thanks for contacting us through our Ask the Engineer page. 

Yes it is possible to rework the foundations to provide a more level floor system at your home. The primary goal, however, is to stabilize the home to ensure the settling does not continue. Re-leveling is typically considered a cosmetic step that follows stabilization. Sounds to me like someone has made attempts to stabilize the main level floor framing by installing retrofit 4×6 posts. Unfortunately, I find that most of these retrofits installed by homeowners or fly-by-night contractors do little to provide permanent stability. You may need an overview structural inspection in order to wrap your arms around the extent of the problem. Best case scenario, we determine that the house is stable but out-of-level and you can call it “character” in an older home. Worse case scenario… you need to redo the “temporary” posts and footings and push the floors back into position. 

We can send out a technician to give you a free estimate for repairs or, for an inspection fee of $500, we can provide you with a structural inspection and report listing required repairs from a professional structural engineer licensed in the state of Georgia followed by a cost proposal to execute the plan. 

Give us a call at 678-290-1325 and we’ll get you on the schedule! 




Question #2 from Jon: 
Just bought an old (1924) beach cottage on Tybee Island in Georgia. Thinking about raising it just enough to meet local flood level code, but not so high that it looks like its on stilts. Lot elevation is about 7′ now, flood hight is 13, so technically I only need to raise the house 6 or 7 more feet. The issue is I still want to be able to park an SUV underneath. Is it possible to build the new foundation at a level lower than the existing ground and engineer it so it is relatively waterproof? 


Answer from Chris: 
Jon, 
Thanks for contacting us through our Ask the Engineer page. 

The answer is, yes. We actually install foundation systems as deep as 10’ below the existing ground. Of course, it’s not easy and not cheap but it can be done. In your case, special attention should be paid to the waterproofing aspect. I expect that you may need to go 3’ into the ground to give a total clear height of 8’ to 9’ inside the garage area. As long as the water table is lower than 3’ below the surface, a typical drain system should do the trick. 

Let us know if we can be of further assistance. 




Question #1 from John: 
I have a block wall in a basement that is sub grade. I have a crack in the mortar joint that runs almost the full length of the wall. The wall is slightly bowed as well. Do you have any suggestions as how to best repair this sort of issue, or does it need to be repaired? 


Answer from Chris: 
Here’s the bad news…YES, the wall most likely does need to be repaired. The crack has opened up in response to movement caused by the lateral pressure exerted by the retained soils outside. You now have a “hinge” joint in the wall that is a great amount weaker than the original mortared joint. Unless you either remove the pressure (remove the soils outside the wall) or brace the wall, the movement will likely continue. 

Here’s the good-ish news… The wall can typically be braced without having to rebuild it. There are 3 main ways to brace a failing wall such as this. 1) Install carbon fiber straps at the inside face of the wall. 2) Install steel “soldier beams” against the inside face of the wall. 3) Install a helical tie-back system. Some options are better than others for certain conditions. 

You need to have an expert come out and determine the proper bracing solution. Make sure you retain the services of a company with a great customer service reputation, a true lifetime of the structure warranty and a license to practice structural engineering. (Warning: sales pitch ahead) We are the only company in Metro Atlanta that meets these criteria. If you are in Metro Atlanta, call us at 678-290-1325 and we can get you scheduled for an evaluation by a licensed structural engineer.