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Sawn beam pocket


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This beam pocket in a 9' basement wall was saw cut instead of cast. All of the beam pockets are simular. The original pockets were cast, but for some reason were lowered (9' wall maybe?)I haven't come across this method and was wondering if it is acceptable or deficient. This area has a crack that has leaked where it intercepts a cold joint but shows no movement. This foundation is 9 years old and holding up a manufactured home. In your opinion, how should I report this?

Thanks for any help,

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P.S. Notice the professional plumbing and electrical installations.

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If you give the situation a little thought and put it in proper perspective, in spite of all of the conditions you've mentioned, a reinforced concrete foundation is able to bear so much more weight than a home that it's hardly worth talking about.

According to a local manufactured home transportation department, the average modular home ranges between 56,000 to 100,000 pounds. The average bearing capability of concrete is typically better than 6,000 psi. Assuming the home was 50 by 30 and weighed the maximum weight of 100,000 pounds, that would translate to roughly 500 pounds per linear. That, in turn breaks down to a whopping 5.2 pounds per square inch applied to the the surface of the foundation top and center beam. In light of all of this, even the weight applied to the beam pocket by the center beam, is pretty insignificant.

The only thing I would want to see is that the steel bearing plate under the center beam was set in high psi grout.

In cases like this you have to wonder if we are qualified to say anything more or less than to describe exactly what we see and express a mild curiosity or concern as to whether the building department actually blessed it as it is. If you aren't seeing a portion of the concrete under the beam bearing that is stressed and cracked, it's most likely fine. Since in the ideal world, the half-life of concrete is some ridiculous figure like 100 years, the concrete is still a bit green. If it hasn't begun to fail yet, it probably won't.

I personally would not loose much sleep over it, and could see saying too much become a problem.

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This beam pocket in a 9' basement wall was saw cut instead of cast. All of the beam pockets are simular. The original pockets were cast, but for some reason were lowered (9' wall maybe?)I haven't come across this method and was wondering if it is acceptable or deficient. This area has a crack that has leaked where it intercepts a cold joint but shows no movement. This foundation is 9 years old and holding up a manufactured home. In your opinion, how should I report this?

Thanks for any help,

P.S. Notice the professional plumbing and electrical installations.

I can't tell you how to report it, but cutting a pocket in a concrete wall is almost never a problem.

- Jim Katen, Oregon

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You're right, Jim, now that you've made me think about it more. I'm glad you questioned it. It's been so long since I've needed to think about any of this.

A quick google refreshed my memory: Residential concrete shoots for 2500 psi and anything within 500 psi is considered acceptable. Commercial concrete shoots for 4000 psi. The maximum psi attainable psi appears to be 7000 according to the Portland Cement Association.

So, that slightly more than halves my original calculations which means that the average residential foundation can bear about 500 times more weight per square inch than its asked to. Even at the new figures, the load applied to the beam pocket is pretty insignificant.

Again, probably the most important factor with steel would be bearing it on a steel bearing plate, which is set in high psi grout to properly apply the load to the concrete bearing surface.

Whew! It has been too long...

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3000 PSI is the common mix around here with high strength in the realm of 5000 PSI. Flat work is mostly reinforced with fiber, with steel reserved for heavy loads like bus garages, factory floors, and road beds. Cure rate, working characteristics and load ratings are further refined with additives, aggregate size and composition, adjusting the mix recipe ratios, the amount of air entrained in the mix, and even the number of turns in the drum. The mix for a bridge deck on a State road in NY can satisfy all the test standards and be rejected if it sees more than 100 revs before placement begins.

Tom

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Thinking about all this brings back the memory of an incident that is funny now, but was far from funny when it happened.

We were in the middle of a pour on a formed and reinforced concrete foundation for an office building. One of our 'home from college for the summer' laborers was manning a vibrator and got it hung up in all the reinforcement steel. He never alerted us and just kept trying to free it in a panic. Unfortunately, the first we knew of it was when the form finally ruptured. What a nightmare that became.

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So, that slightly more than halves my original calculations which means that the average residential foundation can bear about 500 times more weight per square inch than its asked to. Even at the new figures, the load applied to the beam pocket is pretty insignificant.

For the purpose of discussion, the beam may be carrying much more than the average weight per linear foot. Plus, it may be carrying 50% of the live loads. Every structure is different but the load on the beam could easily be from 10k lbs through 25K lbs. So each pocket may have 10 or 12k lbs to support. Call the point of contact 20 square inches (and many installations have less than that) it ends up being around 600 psi.

I agree that the pockets are fine.

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Yeah, I started to go down that road, regarding probable loads applied to a pocket, and the array of possible structural layouts above made the range of possibilities too wide to arrive at an average figure. I found myself considering the fact that a center beam won't bear much, if any, weight from the roofing system, yet bears twice the live load that the perimeter walls do (per floor, so it would be doubled again for a second floor with a load bearing center wall) along with possible loads from the upper floors transferred onto it by a column. So, it does begin to add up quickly.

Any way you cut it though, a concrete foundation is taking a walk in the park supporting a residence.

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This is a typical installation for HUD code manufactured homes when installed on full basements. The defining element of the HUD code home being the full-length steel beams carrying the floor system. The transverse beams supported at the beam pockets carry the entire home load transmitted by the full-length beams of the home, of course double-wides will have a center lally column. The required number of transverse beams will be specified by the home manufacturer. There is routinely no support at home perimeter unless specified by snow load requirements. If this is a double-wide installation, a key item to note, that is often overlooked, is a support from the center of the transverse beam to the marriage wall band joists. Please excuse any posting errors as this is my first time!

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This is a typical installation for HUD code manufactured homes when installed on full basements. The defining element of the HUD code home being the full-length steel beams carrying the floor system. The transverse beams supported at the beam pockets carry the entire home load transmitted by the full-length beams of the home, of course double-wides will have a center lally column. The required number of transverse beams will be specified by the home manufacturer. There is routinely no support at home perimeter unless specified by snow load requirements.

Thanks for pointing this out, Greg.

The steel frame carries the weight of the manufactured home and is generally narrower than the home.

Notice that in the OP's pic, the steel frame is resting directly on the foundation wall, so that spreads the weight and, as everybody has said, there should be no problem with those beam pockets.

In cases where the frame is narrower, I think the transverse beams under the frame carry much more of the weight than they would in typical home construction, where the walls of the home rest directly on the foundation walls. I dug up a couple of pictures that show this. The OSB walls of the basement are more for skirting than support. One pic shows the end of an I-beam resting on the plate, not very well supported. I think most of the load was on 3 8X8 wooden beams with central steel jackposts. About a 50 ft double-wide.

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Thank you all for your responses. I've only been inspecting a few years and sometimes worry too much when I see the unfamiliar. I was concerned about the radii of the overcuts somehow isolating the bearing surface. After thinking about what was discussed I don't see this as a problem anymore.

Thanks again.

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Hmmm.. Is that a square steel tube under the beam? That's what it looks like. That's funny. I also used to detail steel. (The ADD mind at work - a wanderer until I finally found a home in home inspections). We never would have found a tube as an acceptable bearing plate. A steel tube isn't designed to receive weight that way, but if it hasn't collapsed or mis-shapen yet, I guess it's ok. As Sargeant Schultz, of Hogan's Heros used to say, "I see nothing... " [:-bigeyes

Don't worry about it Hoosier, I'm just surprised by the off the wall (or to put it more accurately 'out of the back of the truck') materials choice. It's fine...

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Brilliant, Jim!... I love it...

You know? I really wish I hadn't seen that tube. The steel of the square tube is at least half the thickness of the web and flanges of the I-beam that was, most likely, engineered for that application. The tube, unfortunatly, truly is the overload indicator. What is happening to the trades? Are there any true tradesmen left or are there merely guys who made it through another week to collect another paycheck?

I'm not a big union fan, but there is a LOT to be said for forcing a tradesman to go through a very structured deliberate apprenticeship with levels of accomplishment and earned designations, which instill a sense of pride in both the trade and the workmanship.

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Having inspected some 500 manufactured homes for FHA loan approval, I see nothing wrong with the pocket being cut out versus cast, as long as the job was done without cracking the concrete. At the least, the installer did not try chipping the pocket out.

BTW, maybe some folks do not know that most manufactured homes are constructed to be supported on piers when installed over a crawlspace, in which case the perimeter wall is not load bearing, per se. The per se being that HUD rules, as adopted by the states, requires that some perimeter openings, such as doors and some windows, be supported. Many installers shim between the perimeter wall and the underside of the frame under the edges of these openings.

When these homes are installed on basement (and some crawlspace) foundations, the foundation becomes load bearing. In most cases, transverse beams are used in place of piers under the carriage beams, which means about every 8 to 10 feet. These beams each must have a column or pier supporting the mid-point. Recently, more manufactured homes intended for basement foundations have been produced that are more like conventional homes in that the home is supported around the perimeter by the foundation and a central beam running the length of the home. The central beam is supported on columns or piers.

However, I have another concern in looking at the picture, for homes supported on transverse beams, EVERY end of the beams are supposed to be anchored to the foundation. Additionally, a problem I often find is that the carriage beams are supposed to be welded or bolted to the transverse beam at EACH point where they cross to complete the anchoring of the home. I usually find transverse beams anchored to the foundation, but the home not anchored to the beams. For all purposes, if the home is not attached to the transverse beams, it is not anchored. For homes with a central beam, anchoring is to the foundation, usually using pipe strapping every 6 feet as required by the codes.

If in doubt about how a manufactured home is installed, be sure to record the home's manufacturer, where the home was manufactured (because many MH manufacturers have multiple plants or used to before the bad times), and the serial and model numbers. Then call the manufacturer and ask for an installation (piering) diagram to be faxed to you. If the home is newer, the manufacturer might still have the diagrams. Some are better than others. Luck is usually involved, though.

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This is a typical installation for HUD code manufactured homes when installed on full basements. The defining element of the HUD code home being the full-length steel beams carrying the floor system. The transverse beams supported at the beam pockets carry the entire home load transmitted by the full-length beams of the home, of course double-wides will have a center lally column. The required number of transverse beams will be specified by the home manufacturer. There is routinely no support at home perimeter unless specified by snow load requirements.

Thanks for pointing this out, Greg.

The steel frame carries the weight of the manufactured home and is generally narrower than the home.

Notice that in the OP's pic, the steel frame is resting directly on the foundation wall, so that spreads the weight and, as everybody has said, there should be no problem with those beam pockets.

In cases where the frame is narrower, I think the transverse beams under the frame carry much more of the weight than they would in typical home construction, where the walls of the home rest directly on the foundation walls. I dug up a couple of pictures that show this. The OSB walls of the basement are more for skirting than support. One pic shows the end of an I-beam resting on the plate, not very well supported. I think most of the load was on 3 8X8 wooden beams with central steel jackposts. About a 50 ft double-wide.

Click to Enlarge
tn_20091230154244_basement1.jpg

44.71 KB

Click to Enlarge
tn_2009123015437_basement2.jpg

67.65 KB

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