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    boards.hgtvremodels.com    HGTVRemodels Message Boards  Hop To Forum Categories  Best Practices  Hop To Forums  Framing    sill plate attachment to walls
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sill plate attachment to walls
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posted
My framer is wanting to use straps embedded into the concrete walls (crawlspace) to attach the sill plate (instead of using anchor bolts). Has anyone had any experience using these? They obviously can't anchor the walls down like anchor bolts can but would it matter since the weight of the house is substantial (2-story)?
 
Posts: 12 | Location: Lake of the Ozarks, Missouri | Registered: 07 November 2006Reply With QuoteReport This Post
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If the straps are actually designed for the purpose, and are so designated by their manufacturer, and if they are code-approved in your area, they may be acceptable. I personally still prefer bolts.


Architect (NY) and Home Designer (PA)
 
Posts: 2870 | Location: Tobyhanna, PA | Registered: 24 October 2005Reply With QuoteReport This Post
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quote:
The straps just don’t work as well. What happens is when you backfill and the wall loads up with pressure as the dirt settles over time. The wall will start to slip out from underneath the sill plate. The straps let the wall twist just a little. The bolts are much better.


This is nonsense.

Straps are designed to carry equal loads as bolts and when applied according to design will not move at all.

Joists temselves when properly anchored to the sill plate also resist the lateral loads imposed by backfilling.

And there is no less load immediately after backfilling than after a period of time.

The height of unbalanced fill and type of soil is what determines lateral loading on a foundation wall.

Lateral loading can be eliminated almost completely by cutting back the trench at a 45 degree angle, the angle of repose, then backfilling with crushed stone.

The bottom line is that straps are not inferior to bolts, and are recognized by testing and Code authorities as equal...
 
Posts: 453 | Registered: 19 July 2005Reply With QuoteReport This Post
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quote:
The explain why many engineers are moving away from straps. Is it because many houses as they progress in age.


No. I do not need to prove you WRONG.
YOU need to support your claims with engineering calculations and numeric facts and prove yourself RIGHT.

And since you are NOT an engineer, I do not suppose you can do that....and must dismiss your claims as those of someone who doesn't have any idea what they are speaking of.

If you check Simpson, USP, and examine the Evaluation Reports of the National Model Codes, they contradict your claims and rank straps as equal to anchor bolts (or better) when properly installed.

quote:
"Some contractors also don’t pull them tight. Some times the nails pull loose. And some times they just rust off. I have seen this all happen and anyone that wants to see they can come to Columbus and I will show you."


Now, you are talking about something else altogether: straps improperly installed by contractors will fail just as regularly as anchor bolts improperly installed by contractors.

You mixed up apples and 4 barrel carburetors.

Properly installed, strap and bolts perfrom equally....and I don't have to come to Columbus to see that....

All I need to do is READ the 3rd party tested and approved nationally accepted LITERATURE......
 
Posts: 453 | Registered: 19 July 2005Reply With QuoteReport This Post
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Confusing the issue with facts again, homebild, eh?


Architect (NY) and Home Designer (PA)
 
Posts: 2870 | Location: Tobyhanna, PA | Registered: 24 October 2005Reply With QuoteReport This Post
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Hold me back, Rich....
Hold me back! Wink
 
Posts: 453 | Registered: 19 July 2005Reply With QuoteReport This Post
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What kind of straps is the contractor wanting to use? If they are embeded in the foundation wall they sound like holddown straps, in which case they should not be used to replace the anchor bolts. They are used in conjunction witht the anchor bolts. The holddown straps are designed to resist the overturning moment of a shear wall, and the anchor bolts are to resist the shear or "sliding" of the house on the foundation wall. Both have to be used to keep your house on its foundations. Am I understanding your question correctly?
 
Posts: 2 | Registered: 04 January 2007Reply With QuoteReport This Post
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The straps are embedded into the foundation walls. The framer also drove some very large nails through the sill plate into the walls before the concrete had a chance to fully cure.
 
Posts: 12 | Location: Lake of the Ozarks, Missouri | Registered: 07 November 2006Reply With QuoteReport This Post
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Why the need for staps AND bolts?

Would not anchor bolts with proper oversize washers perform all required functions?

It seems to me, from looking at some strap installations, that straps would allow some minute movement of the sill plate. Bolts would not. The straps just don't LOOK like they will do the intended job as well.


Architect (NY) and Home Designer (PA)
 
Posts: 2870 | Location: Tobyhanna, PA | Registered: 24 October 2005Reply With QuoteReport This Post
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Because they are designed to do different things. As I explain this it is probably nothing new to you, but bear with me. As a house sits on its foundation walls it is subject to lateral and gravity loads. The gravity loads are resisted by footings, which support foundation walls, which support stud walls, which in turn support the roof system. As long as there is a continuous load path from top to bottom strong enough to support the loads, gravity loads are taken care of. That part is easy. The lateral loads, such as wind and seismic, act on the structure in the form of shear. Roof diaphragms and shear walls resist this force, but must also have a continuous load path to the foundation walls. Basically the force wants to slide the house horizontally off the foundation wall. The number and spacing of anchor bolts is determined by the amount of shear force per foot of wall length. This is what anchor bolts are designed to resist, the horizontal sliding of the structure along the foundation wall. However, this is not the end of the effect of shear on a building since we do not build homes (or anything else) without openings. The straps that I am referring to are more commonly referred to as hurricane straps or seismic straps. These straps are designed to resist the uplift that occurs at the ends of shear walls. The amount of uplift in a wall depends on two things: the height of the wall and the length of the wall. This is actually easier to do with pictures, and I hope I am not boring you. Anyway, the shear force acts at the top of the wall creating a moment force that will tip the wall over; the taller and the narrower the wall the less force needed to tip the wall over and the larger strap needed to resist this force. Of course, the shorter and longer the shear wall the more force required to tip the wall over and thus the smaller the strap needed at each end of the shear wall. The first question I expect is why won’t more anchor bolts at the corners and ends of shear walls work like straps? In my area the seismic and wind forces can be very high, but the limiting factor in the strength of the connection is not the tensile strength of the anchor bolt, but the weakness of the sill plate. By using both straps and bolts, all the lateral forces are accounted for and a continuous load path exists to resist them. In some areas of the country seismic straps are not needed, it all depends on the amount of lateral loading, and the code which is used. However, straps should never be used to replace anchor bolts because they are not designed to replace them.

Chris at first glance I am sure that even masonry nails through the sill into the conrete would not give the same resistance that anchor bolts would, but I am not in your part of the country (I assume), and I don't know what code your jurisdiction has adopted, but your inspector "should" catch any mistakes by your contractor. That doesn't mean the inspector will catch mistakes, but you should ask questions if you are not comfortable with how something is being built on your house.

JFYI Engineers are not moving away from straps. The Proscriptive code relating to the shear resistance of narrow support walls (one example: garage wall returns)requires straps rated at 4200 lbs or better, and must meet minimum width requirements. You can find a great example of this in the APA website by searching under Portal walls. The newest IRC code also has several good illustrations on portal walls for garages or other narrow shear walls. Engineers use portal walls all the time, but instead of using the proscriptive codes engineers actually use the formulas to design these walls.

Good Luck
 
Posts: 2 | Registered: 04 January 2007Reply With QuoteReport This Post
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