Piers-Part 2-Cap Blocks & Spacers & Shims!

Last week we talked about pier footings, today we need to look at the top of the footings, the cap blocks, spacers and shims.

The job of the pier cap is to take the all the weight from the I-Beam and spread it out over the entire surface of the Concrete Masonry Unit (that is fancy talk for concrete block). So, we are taking between 5,500 and 6,900 lbs. concentrated in the 3″ flange of the chassis beam, and spreading it out over the top of an 8″ x 16″ block.

Double block piers need double cap blocks!

Keep in mind, while a concrete block is very strong, it is also very fragile. But I think you would agree that it is very rare to see a concrete block fail if it was properly loaded and supported. While the footing provides the support, the cap blocks handle the loading! If the pier is made of single stack blocks, the cap must be 8″ x 16″, if double stack blocks, the cap must be 16″ x 16″.

Also, if capping double block piers, with two 8″ x 16″ caps, the joint in the cap blocks must be at a right angle to the joint of the blocks being capped. AND, the joint in the cap blocks must be at a right angle to the chassis beam.

Generally, the cap block must be 4″ solid, pre-cast concrete or 2″ x 8″ x 16″ pressure treated lumber. Most installation instructions also allow ½” steel to be used as a cap, but I have never seen this in the field (if you use steel, could you send me a picture?).

These are NOT hardwood shims!

1″ concrete broken-Where is the shim??

Shims are needed between the I-beam and the cap block. While a few manufacturers might suggest that shims are optional, I think they are very important and I highly recommend that you always install shims in your installations. Shims need to be used in pairs and should only take up 1″ of space between the cap block and I-beam. Most shims are hardwood (usually made from locust or oak) 4″ x  6″, however ABS shims are also available. One thing about the ABS shims is that them have grooves that lock them together so they can’t slip apart.

Spacers are needed if you have more than 1″ of space between the cap block and I-beam. Manufacturers differ somewhat on what you can use as a spacer. Some say a maximum 2″ thick hardwood lumber, or a 2″ or 4″ solid block (I assume that this manufacturer allows 1″ hardwood as a spacer as they don’t indicate a minimum). Yet a another manufacturer allows the use of two layers of 2″ lumber. Most manufacturers simply say 2″ lumber or 2″ to 4″ solid concrete.

1″ concrete spacer not permitted.

For me, the take away is that the use of 1″ concrete is not permitted, and most installation instruction do not permit 1″ lumber. Sorry!

Just remember, you want to spread out the load to as large of an area as possible. So be sure your cap blocks are the same size as the pier. Be cautious when selecting spacers and shims.

As always, verify your installation practices to the manufacturers installation instructions that come with the home!

Ok, next week we will take a closer look at the pier itself!

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Breaking Down Pier Construction-Part 1-Footings

So far this month, I have had the chance to work with over 50 professional installers over several different training opportunities. One thing that became evident is that we all need to improve our understanding of the most basic part of a manufactured home foundation, the piers and footings.

When examining our support piers, I think it best to drill down to the bottom and work our way up. And at the bottom of every pier is the footing. Basically, the job of the footing is to spread the pier load in a way that keeps the pier from sinking into the earth (I like to compare a footing to a snow shoe. It keeps you from sinking into the snow by spreading out your body weight over a larger area).

There are three things you need to consider when you are determining what size and type of footing to use:

1.       How much weight will the footing have to support?

2.       How much weight can the ground under the footing support?

3.       Will the footing shift or heave due to frost penetrating under the footing?

To be straight with you, there is a lot of information in our industry that is peppered with wiggle words and qualifiers that can mislead or misguide professional installers. I will do my best to just give you the facts based in the building science that I have examined.

Typical Pier Load Chart

In general, a pier supporting the manufactured home along the frame (you may call it the chassis), spaced every 8’ will need to support approximately 5,500 lbs. in the South roof load zone. If you are installing the home in the north roof load zone, you are looking at up to 6,900 lbs. These loads include the actual weight of the home, the assumed weight of people, furniture, the other contents inside the home (live load), and the anticipated weight of snow on the roof. The pier load charts in the manufacturers installation instructions are where you will find the actual load per pier. Since most of the country is in the South roof load zone, we will assume that each of our piers will need to carry 5,500 lbs. 

Unfortunately, too many professional installers don’t put much thought into how much weight the soil can carry (AKA Soil Bearing Capacity). So either they use the default approach, or just do it the way they have for years. The default approach is found in the International Residential Code and referenced in the manufacturers installation instructions. This basically allows you to assume 1,500 lbs. per square foot soil bearing capacity for a decent, typical, well drained site.

So, if my pier load is 5,500 lbs., and my soil can carry 1,500 lbs. per square foot, I need to spread the load out over 3.6 square feet of earth (5,500 ÷ 1,500 =3.6). But you should go to the charts in the installation instructions where the math is done for you. This chart shows a 24” x 24” footing is needed, slightly larger than the 3.6 we calculated.

Footing must be smooth and flat! This is certain to fail!

 

If your footings are poured in place concrete, they must be at least 6” thick and depending on the load and soil bearing capacity, possibly thicker. The chart above requires our footing to be 8″ thick.

mushroom-footing

Poorly constructed footing

When you order the concrete, make sure the “footing mix” you request is 28-day compressive strength of 3,000 psi. In checking with a few concrete suppliers, there was some variation. Be certain that you finish the concrete to provide a flat, smooth, and level surface for the pier to rest.

If you use pre-cast concrete, they must be at least 4″ thick, meeting with the ASTM standard C90-02a. Patio slabs from the garden center generally do not meet this standard.

Listed and labeled ABS plastic footing pads can be used where protection from frost has been provided, or if the pad is placed below the maximum frost penetration line.  

Ok, so we now know that our load on the pier is 5,500 lbs., and our footing will need to be 2 feet square as determined from the chart. But what about the construction of the actual pier? Almost every installation manual states that a single 8” x 16” concrete block can carry 8,000 lbs. (just stay under 36″ high). So, your pier can be constructed with single blocks that can easily carry the 5,500 lbs. load (If you are installing a Clayton product, they limit a dry stack, single block pier to 5,760 lbs.).  Make certain you look at the specific installation instructions for the home you are installing.  

In the Middle and North roof load zones, the piers loads are a little greater, and remember that not every home is the same! Next week we will talk about frost protection, the cap blocks, shims, and spacers that are needed to complete pier construction.

Personalized Small Group Installer Training Available!

Last week I traveled to New England to present a HUD Manufactured Home Installer Training course specifically for a community owner and his crew so they could get their HUD Manufactured Home Installer License.

Friday morning I received an email from that community owner that I wanted to share:

  • “The course was great and we all learned a lot, but more important the understanding behind the license makes sense. The explanation & knowledge you have from HUD & industry is important to this process… 
    The real installer needs the license attained in this fashion.”

I had to agree! Working with this small group allowed us to focus the training on areas of greatest need, and we were also able to highlight the manufacturers installation manuals specific to the homes they sold/installed.

So retailers, community owners, manufacturers, installers, etc., if you would like to coordinate a HUD approved Manufactured Housing Installer Training for your smaller group, contact me and let’s see what we can work out!

Mark

markconte3@yahoo.com

Safety Pays!

 

My grandfather Giovanni Battista Conte

My family has been in the construction business ever since my grandfather immigrated from Italy in the early 1920’s. Having five sons, my grandfather always had an in-house work crew and back-log of work. Not only was he a skilled carpenter, but he was extremely frugal  and always looked for ways to save time and money. Unfortunately, his focus on saving  time and money  failed to include working safely. Eventually this ended up costing him dearly. You see, when my grandfather was in his mid-twenties, he lost his little finger on his left hand using a circular saw with a broken guard. To compound this injury, about 10 years later, he lost his right arm to the elbow as a result of severe laceration, again the result of overlooking his own personal safety.

These accidents ended up costing him much more than he ever expected and made a big impact on me. Every time I visit a manufactured housing installation site, I see professional installers placing their health at risk, just like my grandfather.  I  hope that this post might prompt you to examine job site safety to reduce the risk of injury for everyone involved in manufactured housing installation. Stay with me as I touch on a few things for you to consider.

First Aid Kit-This is a must at every job site. Make certain that all trucks in your fleet have one, and that they are fully stocked at all times. You can’t predict when an accident might happen!  

Eye protection-Over 500,000 job related eye injuries requiring medical attention occur every year. Don’t allow anyone on the job site without proper eye protection. In fact, you should have a few extra pairs of safety glasses or googles in your truck (with your first aid kit) at all times. In general, prescription eyeglasses add some level of protection, add some side shields and you are in great shape! Watch out for workers wearing cheap sunglasses as a projectile can shatter the plastic lens and lead to more injury.

Also, sunglasses are never to be used to protect your eyes during welding, acetylene burning, or cutting work. Sunglass lens are NOT the same as welding or cutting lenses!

Back injuries-Over 1 Million on the job back injuries occur annually. Make sure you and your crew practice proper lifting techniques. Bundles of shingles, boxes of siding, concrete blocks, sheets of plywood or OSB are heavy. Take a few extra minutes to plan ahead to reduce the probability of back injury. Work smart – Not hard!

Fall Protection-OSHA requires personal fall protection for anyone working 6’ or more above the next lower level. ThatABC-of-fall-protection means a properly fitted harness every time you are working on a roof. Visit OSHA.GOV for more information on this.

Suspended Loads-NEVER allow anyone under a suspended load. Cables and straps can break, loads can shift, spreader bars can fail, and rim joists can split. Make sure if the home were to drop, it would be supported by cribbing, and not be on top of you or your crew!

Footwear-There are 1.2 million job related foot injuries per year! In our industry, footwear should have slip/puncture resistant soles and a steel toe. No sneakers on the job site! Actually, once a worker starts wearing work boots, they won’t go back to sneakers! Especially those with time working on a ladder!

Tools-Never use a nail gun without a properly working safety mechanism. Never use a nail gun like a hammer to finish driving in a nail or staple, or as any type of striking tool. Make sure all saws have the proper guards in place, and the work piece is secured and supported to prevent injury.  Double check the placement of all jacks and winches (come-alongs). Position yourself so that in the event of a slip, you are in the clear. When using an impact wrench, make sure to use impact sockets, not hand ratchet sockets. Don’t use a screwdriver as a chisel or pry-bar. Only use a tool as intended,  I think you get the picture!

Electrical Service-Make certain every tool and cord is powered by a GFCI protected circuit or extension cord!

gfci-power-extensions-tower-manufacturing

Ground fault circuit interrupter cord. 

Immediately replace damaged or frayed cords.  

Ladders-I can’t tell you of all of the risks I see being taken with ladders. Make sure you buy high quality (I prefer fiberglass) ladders that are the right size and capacity for the job . Inspect your ladders every day before use, replace worn out ropes on extension ladder pulleys, and steer clear of power lines!!! A ladder standoff is a very valuable tool.

b8e3a590-33a7-49a6-ac04-bfb74cfa8251_1000

Ladder standoff

Read the warnings on each ladder and believe them!

 

Clothing-I am a big fan of work uniforms for several reasons. But the biggest reason is safety. When properly fitted, they provide added protection from many hazards. Plus, you and your crew will look professional and your customers and potential customers will be impressed. Gloves must fit your hands snugly, and shirt tails should be tucked! I know a lot of you think that in the summer, a work uniform would be too hot to wear, but back in the day, my crew wore them and found they were more comfortable wearing work uniforms. And the cleaning service was well worth the price.

Housekeeping-There have been countless injuries because of messy job sites, such as stepping on hidden nails in piles of debris, and tripping and slipping. Not to mention time lost looking for tools, materials, etc. Keep things tidy as you go. You will realize saving in time, money and safety!

Distractions-Everyone knows that distracted driving is a problem, but do we realize that distracted working is just as dangerous? Have you considered having your work crew leave their cell phones in the trucks? I see too many guys on jobs sites paying more attention to their smart phone than their jobs. For their own safety, make them put their phones away.

 

OK, these are a few things to start the discussion. I would love to hear what you have to say.

We need to practice safety and not learn it by accident.

Electrical Crossovers

While inspecting some multi-section manufactured home installations recently, I noticed some areas needing improvement regarding electrical crossover connections.  So I thought we should talk about this issue as we head into the summer season.

Should not be exposed!

One of first things to keep in mind is that you should never have any Non-Metallic Sheathed Cable (also called NM Cable, often referred as Romex®) used for branch circuit wiring visible under a manufactured home. Crossover wiring is always to be tucked inside the floor cavity or walls, and protected with an access panel or hatch.

Molex brand connector. Look closely for release tab.

Secondly, to make this connection most manufacturers generally use either electrical connectors or junction boxes. Connectors are pretty straight forward, just snap them together. Most manufacturers in the northeast use Molex® brand connectors, and the great thing about these connectors is that they have release tabs so you can separate the connectors without any damage and reuse them as needed. This is important for relocating a home, or if the home were on display before being moved to it’s installation site.

This brand has no release mechanism.

Some older manufactured homes used a connector made by Amp® that was a single use connector. If you looked closely, you would see: “One Time Use Only, Do Not Re-terminate. The issue was there was no release tab on these connectors, so if you pulled them apart the plastic housing would bend and distort the device. When reconnected, the housing wouldn’t be able to connect securely and safety became a concern. The good news is that I haven’t seen these used for at least eight to ten years. But be alert if you are installing older homes as you may see a connector that is not intended to be reused. If so, cut it off and either install a new connector or use a junction box inside an access panel in the floor cavity or marriage wall.

Look closely to see grounding screw.

Greeny grounding type wire nut.

Speaking of junction boxes, here are a few basic things to remember. Where the NM Cable enters the junction box, there should be a cable clamp or connector. Don’t overtighten the clamp onto the cable, just snug it down. The cable should be secured within 12” of the clamp or connector (check the actual installation manual as some require cable securement within 8” of the cable clamp). If the junction box is metal, it should be grounded. You can use a ground clip, ground screw or a “greeny” wire nut for this.  Twist the conductors together before installing the wire nut, and make sure to use a wire nut that is the proper size. Usually the capacity and number of connectors are identified on the top of the wire nut itself. After grounding the junction box and making good connections, place the cover on the junction box!

I am seeing a few of the push-in type connectors in place of the twist style wire nuts, and these seem to work fine. Just make sure you strip the conductor with the proper tool to the proper length per the installation instructions. I saw a few brands of these push-in connectors that limited their use to solid wire only (no stranded wire). On solid wire conductors, these push-in types are generally reusable. But it can be difficult to get the conductors to disengage. You may be better served replacing them.

If you notice that the outer sheathing (or jacket) of the NM Cable is nicked or damaged, make sure you address it properly. If there is a superficial nick in the outer sheathing, wrap electrical tape around the cable at the nicked area, to a thickness that equals the depth of the nick. If the damage exposes any of the conductors or the paper inside the cable, the affected area must be removed! There is no repair for damage that significant.

End wall crossover. Cables need better protection!

If the manufacturer notched out a wall stud or other structural member to run the NM cable, make sure to protect the cables with wire protective plates or “mash or smash” plates as they call them in the south. And make certain the cable is 100% protected!

Always replace the access panels or close the access area to protect the connection from moisture and possible damage. If any floor insulation is missing, replace it as well!

Revisit the manufacturers installation instructions for a little more detail. On a new home, use the connector type the manufacturer provided.  If there are problems making this connection on a new manufactured home, take a picture and report it back to the manufacturer. They can only make improvements if they get feedback from you!

Keep in mind that you should always refer to the Manufacturers Installation Instructions, but if you want to learn more, the Manufactured Home Construction & Safety Standards (MHCSS) at 3280.801 is where you will find the actual code requirements.  Click Here for the MHCSS  Also, it is worth knowing the MHCSS adopts Article 550 of the 2005 National Electric Code. So, check them all out to make sure you are doing things right!

The Importance of a Good Marriage (Line)!

A good marriage is critical to your emotional and financial security.  The same can be said about the marriage of two or three sections of a manufactured home. For all of the good work and craftsmanship that goes into the construction and installation of a manufactured home, I can’t help but think that the marriage line joint is the weakest link in the process. If the marriage line is not secure, level, and reasonably tight, problems are sure to creep in! Heat loss, wall and ceiling cracks, carpets and floors shadowing the seams, and doors binding can all be symptoms of a good marriage gone bad.

 So, let’s talk a little about the marriage line to make sure we are doing all we can to strengthen this weak link.

Everybody knows to remove all shipping plastic from the home. But it is especially important along the roof line as venting of the roof cavity depends on air flow from one home section to the other. Any plastic left around the roof line can restrict the air flow to properly vent the roof.

Look closely for the staple!

Inspect the marriage wall for leftover staples or nails once the shipping plastic is removed. I know they are a pain in the neck, but one staple left in the marriage line can cause big problems.

Damaged heat duct crossover gasket.

Inspect the heat duct gasket. If it is damaged, you need to replace it. Was it the shipping plastic or straps that caused the damage? If so, snap a picture and let the manufacturer know! Consider a shield made from coil stock that can be removed once the home is in place.

Look for any electric cables that might get pinched or otherwise damaged when the sections are pulled together.  Re-secure them to prevent damage.

Gasket needing inspection!

Is the marriage line gasket intact? Damaged? Properly placed?  If you read my previous posts, you should know I think this is a big problem area. Read my post from April 17, 2017 “Would You Like That Supersized?” for some other thoughts on this gasket.

Gaps between the A and B sections of a home can lead to structural problems over time. While professional installers generally don’t pay much attention to shear walls (the walls that transfer wind loads through the structure of the home to the anchoring system), it is very important to understand that in many two-section manufactured homes, all of the shear walls are found in only one of the sections. The manufacturer is depending on you to make a structurally sound joint to transfer these wind loads across the marriage line to the section of the home with the shear walls.

Wind loads are safely transferred only when you properly fasten the sections together. Basically, a structural, tight fitted joint is required in order for the home to withstand wind storm. No gaps in marriage line!

The manufacturer’s installation instructions states, “Shim any gaps up to one inch between structural elements with dimensional lumber. If any gaps exceed one inch, re-position the home to eliminate such gaps”Read that carefully. It means gaps are not permitted! You must either use shims up to 1″ or get the home sections closer.

mate line 1 gap

This needs a shim!

This is very important not just at the floor, but the walls and roof as well! Gaps between sections can cause the screws, nails, or lags to shear off, pull out, or fail at the exact time they are needed the most!

These lags should have been staggered!

Make sure to stagger your fasteners (A half/B half), and be sure they don’t split out the lumber. The lags or screws you use must properly penetrate into the receiving members by 1 ½”. You might need to use longer fasteners than the ones provided by the manufacturer.

Strapping at roof line.

If you are using straps at the roof, it is critical to remember that this joint also needs to be solid and tight. If the staple crowns or nail heads cut through the strap material, the strap won’t be able do the job that the manufacturer intended.  Make sure your fasteners go through the blocking, beams, or rails provided, and not into the truss!

Take a few minutes before your next set and double check the manufacturer’s instructions for fastening the marriage line. Take a lot of pictures, and give some feedback to the manufacturer (the Quality Assurance Manager in this case). They might be able to tweak things at the factory to make your job easier. In fact, if you aren’t on a first name basis with the QA Manager at the factories you deal with, you need to change that. These guys are a wealth of knowledge! Every QA Manager I have ever met wants to produce the best homes possible. What they are lacking is feedback from you!  

A good, strong, tight marriage line is not always easy and at times very difficult. But, with a little tender loving care, you will get that good marriage line, and we all know, a good marriage is well worth any price!