The Elephant In The Room – Stringer Strangeness / Stringer Stress

 

The Elephant In The Room – Stringer Strangeness / Stringer Stress: Whats WRONG Here?

stair / floor framing

This is under the basement stairs of a nice looking home less than 2 years old.   There are a few things wrong in this photo.

Can you spot all five structural defects?

Here are a few hints;

1 – The riser of the last tread and one joist do not a double trimmer make.

2 – Toe nailed joists do not carry weight, Forever or for long.

3 – Nails are pins to hold framing in place. Weight bearing framing has to be under the load.

4 – Zippered nailing or stitched nailing will not be secure over time. A power nailing defect.

5 – And, yes..the elephant in the room; the stringers are too short on one end. Guess which end.

 

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1

missing double header framing

illustration framing

It’s obvious: one does not look like the other.

There is neither doubled header or trimmer joists present.

What you see in the photo is only a single joist and the face or ‘riser’ of the top tread is nailed to it.

But that is a finishing piece and has no structural strength or function.

So there is no doubled header floor joist at all and even it there were it would be in the wrong position.

In fact there is no correspondence between the text illustration and the actual construction here at all.

Corrective supports and framing are required to make this safe and secure.

I wouldn’t bother to get a price from this builder. No point.

 

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2

error no joist hanger

You’ve seen movies where mountaineers climb rock faces with minuscule toe and finger holds. That may be  fine from the comfort of your chair.

But it’s not what you want to see in your floor framing.

Toe nailing is a carpenters technique using small nails at an angle at the ends of studs and other framing to position, aline, and hold parts in place until other cladding or finish materials are applied. There is no strength in these joints and they can easily be adjusted in various directions.

Here this sideways nailing was used but with bigger nasils. They will hold for a time, but not for all time.

Joist hangers are required here, or else you have to go old school. Old school is double notched joists meeting ledgered beams. It works well, just takes a lot more wood and space. Or you could use joist hangers.

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3

face nailed to stud

It’s partially obscured by the pipe but we can see enough to know that the trimmer joist is only been face nailed to the stud.

It’s the stud that carries the load so it should shoulder it. Meaning that it should be under the joist, at least by the thickness of the joist, or the joist should be notched into the stud.

There is no other framing around to carry the weight for this part of the floor and the stairs. Doesn’t matter if there may be a big engineered truss or wood joist on the other side of that wall. There is nothing right here.

Nails, no matter how big are just pins used to hold wood in place. The wood has to carry the compression load. Nails don’t cut it over time. Wood drying shrinkage, rust and vibration will weaken them. (Screws are worse – no shear strength.)

If the wood parts are big enough then bolts can be used but here thats not the case. Cripple studs must be added to the face of those studs to tranfer the load to the slab shoe plate.

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4

too many nails    I call this nailing defect ‘zippering’ because when large bore nails are peppered close together they can cause the wood to be weakened at that place or line.

This effect is just like the perforations on the tear line of a cardboard box or other packaging. The nailing has punched out material there of crushed fibers so now it can easily be broken at that spot.

Here we can see the space from the tread notch to the bottom edge of the stringer (as it follows the stud) has been nailed repeatedly in a tight line.

The nails are holding for now and the problem is not obvious but as the wood ages and dries it won’t ‘grip’ the nails as tightly and the vibration from the stair usage will start to loosen them. Failure will begin with a bounce and squeak developing in the stairs. These nails are all that’s holding up this stringer.

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5

major error

Here we have the big goof. The elephant in the room.

The photo just shows one stringer but they are both are too short. They don’t meet and transfer load to the floor frame as they should. Have a look at the stringers in Figure S1 (above) to see the correct assembly.

I’ve seen similar errors outside on deck construction, which often gets done non-professionally. When I think back to the last time I saw that error I quickly realize that it was only about an hour ago, outside at the rear deck of this house. Hymn….

The frameing at the main stair to the second floor is completely unaccessable as it is behind finished walls and ceilings. Hymm….

So far this guy is batting O and 2. Will he strike out?

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This array of errors is also just one more example of why it is just as important to have a new home fully inspected.

Just because it’s new,  doesn’t mean it’s right.

 

Original blog post on ActiveRain: Link to Blog Post

A Case Of More Not Being Stronger..A Stair Story.

A Case Of More Not Being Stronger…..A Stair Story. (This is # 4 in a series on a single flipped house.)

   nailed stringer L   nailed stringer R  

These stringers have been nailed to the deck framing with a power nailer. An air powered nailer is a great tool. It allows you to drive large nails without tiring you out. So if you want another nail there , it’s just pull.. BANG and it’s in there. And there’s the problem!

Before the common use of these tools that extra nail took some more effort. Sore arms generally set limits on the number of extra or unnecessary nails being driven.

Carpenters had code books, charts and rules that governed the type, size and number of nails used for any type of joint and size of framing. And they learned this though years of apprenticeship and work practice, training and exams.

But even carpenters had to be cautioned when these tools went into widespread use as it’s too easy to use the wrong size nail or put too many in the same area.  And Codes were changed to correct bad habits and practices.

But on this flipped property this is amateur work. No carpenter puts that many nails in this area, let alone both faces of the same piece. On the end of this stringer, in the last 2 inches of wood, how many nails are there? How much solid wood is left, wood that is not split by a nail or two?

There are too many nails (12). They are too big. And there is no solid wood left in the last 2 inches of the stringer. If you removed it and sawed it off at the 2 inch line, little scraps the size of your finger or thumb would fall to the ground.

Prior to the code changes larger framing (deeper) was required to butt the stringers against as a ledger strip had to be nailed. The ledger strip required a triangular nail pattern using nails larger than 4 inches and that required a doubling of the bearing frame.

Then the stringer was notched to bear on the ledger strip (this is where the weight was transferred) and a stringer this size would be nailed like this with two nails on one side and one in the center on the other face. The nails would be galvanized 2 or 2 and 1/2 common. (This is toe nailing, through nailing from the other side of the support frame is better.)

Nails hold the framing in place. The framing configuration transfers the weight. Nails normally are not intended to transfer weight. (The ledger board detail was an exception.)

Now the current codes treat this differently. Correctly sized metal  joist hangers are to be used. Galvanized nails can be used to mount them. Deck or outdoor screws are NOT to be used between the hanger and the supported framing – that has to be nailed – It’s a fire code requirement.

Now look at these photos again. There is no ledger strip. There are no joist hangers. The nails are too big. There are too many of them. They are not galvanized. There is not enough solid wood there to hold these stringers in place.

What keeps it from collapse?

Gravity!

Just like a ladder. And just like a ladder, a side ways push or the base sliding out will cause it to fall. Are the stringers attached to anything at the bottom?…nope!

More nails is not stronger. To many is weaker.

 

 

Original blog post on ActiveRain: Link to Blog Post

The Feet Know What The Eyes Can’t See

This article by my associate James Quarello shows a problem that carpenters are trained to prevent. Some don’t understand this and the results are like what we have here. I wrote a similar article this past January.

You’re walking down the side walk along your street, gazing about, taking in the sights and boomp! You stumble. You look around to see what caused this interruption of stride. You see that your toe caught a rise in the walk that your eyes never saw. Your feet have detected what your eyes were unable to see.

Nice looking stairwayPart of the reason for that is our stride is basically run on auto pilot. It is really quite even and consistent, so when an undetected variation in the terrain occurs, you stumble.

This science of the stride is the reason why stairs need to be constructed with a consistent height. Some slight variation is allowed (a maximum of 3/8″), but the rise from one step to the next should be very close to even. There is also a maximum allowable height. Here in Connecticut that would be 7 ¾”.

On a recent afternoon I pulled up to my inspection and noticed that the home had a beautiful stone wall and stairway leading to the front entry. Once I got myself situated I head for the stairs. Taking the first step I almost had to lift my leg with my hand it was so high. As I continued to ascend my feet were having convulsions trying to find a rhythm to the stairway.

Obviously my feet knew what my eyes failed to see.

Too highTaking out a tape measure it was no surprise I found the stairs height varied greatly. That first bottom stair was 12 inches from the driveway. Much too high as my feet had known all along. As I continued measuring I found stair heights of 10″, 9 ¾’ 9 ½”, and 7 ¾”. I did not find any two stairs exactly the same height. And as you see only one was of the required height.

My guess is these beautiful stairs were constructed by a homeowner or a poorly skilled contractor without permits. Unfortunately to fix these stairs will require some extensive rebuilding. Leaving them as they are will have the feet of those who use them out of sync and stumbling like a groom after his bachelor party.

James Quarello
Connecticut Home Inspector
2010 – 2011 SNEC-ASHI President
NRSB #8SS0022
JRV Home Inspection Services, LLC

 

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Original blog post on ActiveRain: Link to Blog Post