Pier & Beam Question

[MountainDon]

Here's the image (hastily drawn)



Comments, opinions, facts are welcomed.

[mldrenen]

picture on the right is what i've used for temporary bracing, but the method on the left is much stronger (not to mention more pleasing to the eye).

[MountainDon]

I should have drawn the one on the left with double braces, assuming it is in the middle of a run and not at an end. (one 45 on each side of the post)

[mldrenen]

I should have drawn the one on the left with double braces, assuming it is in the middle of a run and not at an end. (one 45 on each side of the post)

i assumed both would be doubled if in the middle of a long run.

[bigcountry]

What is the best way to attach the braces if you are using concrete piers that are attached directly to the beams???

[Don_P]

I'd stick a large plate through the concrete to attach to later... think Frankenstein's neck 

Some random thoughts;

Many nails spread a load out over a greater area than one or two bolts. Wood is not especially strong per unit area so spreading out a load has alot going for it. with many fasteners if one fails it isn't a big deal. If you have one fastener and lose one... its a big deal!

The best way to attach the 6x6 brace into the 6x6 post is to notch a slight shelf, called a table, into the post for the brace to bear against. At the top the brace would have the tip cut plumb 1-1/2" tall and a 2x6 would be fitted between the plumb cuts of opposing braces. we're now bearing the racking forces against larger areas of wood and the fasteners are simply holding the wood in place and not bearing the load.

Plywood or boards nailed across the entire area of brace/girder/post would lock the assembly into a unit and spread out the load over a larger area.

Welded brackets lagged to the post and girder would be another way.

2x6 plates bolted over the face of the post and girder would stabilze that joint.

The head of the engineering department at Va Tech talking about braced decks said that most knee braces as installed are simply something to hit you in the head as the structure collapsed. In other words most he had seen were woefully inadequate.

[bigcountry]

Don_P

So if I am using a simpson bracket embedded into the concrete pier and the girder is bolted inside that bracket I still need to use knee bracing? I have seen it done so many different ways on here and I do not want to cut corners on the structure. This is the only area I am getting confused on. I am planning on breaking ground in April, as soon as the snow decides to stop falling in NorthCentral PA.

[glenn kangiser]

Titen HD screws or similar with washers could be used to attach braces to a concrete pier if another means was not provided ahead of time.  Min about 4 inches or more embedment.  Drill the concrete with the proper size hole and screw them in with an impact wrench.  No inserts required and reusable to a point.

http://www.amazon.com/gp/product/B001I3JC8Y/ref=pd_lpo_k2_dp_sr_1?pf_rd_p=486539851&pf_rd_s=lpo-top-stripe-1&pf_rd_t=201&pf_rd_i=B000CEXFZG&pf_rd_m=ATVPDKIKX0DER&pf_rd_r=1ZMQAQ2TEBRYJ5SMEHHH

[Kiwi55]

It was my understanding that if the post is buried in the ground in concrete, the ground/concrete provides the required leverage and braces are not required. (This might depend on just how tall the posts are).

[MountainDon]

Whether or not a post in the ground or encased in concrete is going to move or tilt will depend on a number of things. The type of soil is one, and what happens to the soil as it gets wetter. Does the water drain away quickly or does the ground become saturated and the earth become slippery mud? I would be concerned anywheres the ground develops ruts easily when wet.

It is my thinking, my belief, that it doesn't matter much what the pier is made of. There should be some connection(s) that prevent the pier from wiggling this way or that if the ground turns to muck.

[glenn kangiser]

Don is correct.  If the ground turns to mush and does not support the post or the concrete around it then the top must brace it or the house will fall over as we saw with the "Pro" whose house fell over when he built in a seasonal swale with no bracing.

With adequate bracing it will continue to stand on the posts until the ground firms up again if the foundation soil under the post is solid.

Providing proper drainage around the site can also help to eliminate problems.  Don't let uphill water get under your house.

[dug]

So if I am using a simpson bracket embedded into the concrete pier and the girder is bolted inside that bracket I still need to use knee bracing?

I think that unless the piers were a long ways in the ground you should still brace them. I built stout concrete piers with beams attached directly to them because at the time it seemed to be the best way to build them. I embedded concrete anchor bolts on the outside face of them so I could bolt 2 by 4's to them to provide a nailing surface for skirting. I wasn't really thinking about bracing but after seeing some major failures due to non-braced piers I added bracing but it is on the outside face of the pier like in Don's second example in the poll, which I think is inadequate. I wish I would have done the "Frankenstein" method suggested by Don P. I hadn't thought of drilling and bolting as Glenn suggested but I may do that now.

Every time the wind kicks up I regret not having provided better bracing for my piers.  

[glenn kangiser]

The Simpson bracket does not provide bracing.  It only provides a good connection to the pier.  You are at the mercy of your soil and mother nature if you don't brace and the soil gets soft. 

Dug has a point.  Your house is a giant sail in the wind.  If a 100 mile per hour gust hits the side of your house it exerts about 30 psf pressure on it.

Lets say about 600 sf exposed on one side for example including roof area.  Likely it won't reach this pressure due to lots of factors we are not considering but side pressure could be up to 30x600=18000 lbs.  Will your piers resist that?

[dug]

I've never been a math whiz but I do remember a guy named Archimedes. If your wall is 20 ft. high I wonder how much force is being exerted on those piers when 30 psf is hitting the top portion of the wall?   

[dug]

Just thinking of my last post I and I guess If the walls and roof were completely ridged than it probably wouldn't change the equation no matter how high the force is above the piers.

[MountainDon]

I think if we assume the box is rigid and the box is firmly attached to the beams it would be safe for purposes of discussion to treat that force as being distributed across all the piers. It gets more complicated than that though as the near side piers likely have some uplift force and the far side may have extra downforce as well as a sideways force. The taller the piers the more pronounced the sideways rotating force on the piers will be. The wind will be trying to tip the box as well as displace it sideways. If the wind is blowing up the sloped roof there are also forces from that, some of which may be acting as a lift on the roof near the peak. That can also increase the downwards and outwards force on the wall from the rafters on the far side.

[MountainDon]

The best way to attach the 6x6 brace into the 6x6 post is to notch a slight shelf, called a table, into the post for the brace to bear against. At the top the brace would have the tip cut plumb 1-1/2" tall and a 2x6 would be fitted between the plumb cuts of opposing braces. we're now bearing the racking forces against larger areas of wood and the fasteners are simply holding the wood in place and not bearing the load.

I believe this is what Don_P means... If I'm wrong Don_P will correct me.



or this?



There would be another brace to the right, butted up against that 2x6 nailed under the girder, heading to the next post to the right.

[bigcountry]

What would be the minimum length and optimum angle for the brace? I plan on having 1-2ft of clearance from ground to bottom of beam depending on the slope of the ground.

[rwanders]

  My pier and beam does not include any angle braces. The piers are 12" poured concrete with rebar. They are embedded 4' into well drained gravelly soil plus "big foot" footers. they only extend 12" above grade to support 4x10 beams. With only 12" of height to install any angle bracing it seemed to offer a minimal amount of bracing forces. Of course, for about 6 months of the year, the ground is also essentially additional "concrete" reinforcing since it remains frozen to about 48" down. Should I be concerned about the lack of angle bracing?

[MountainDon]

My opinion on that is that with Bigfoot bottom ends, 4 ft deep and a small above ground section there is no need in your case. My opinion.

[MountainDon]

What would be the minimum length and optimum angle for the brace? I plan on having 1-2ft of clearance from ground to bottom of beam depending on the slope of the ground.

The last 2 drawings of mine have the brace at a lower angle than necessary, I think. The angle could have been closer to 45 degrees. Install the one slanting up from the left and then the one slanting up from the right. Cut a length of 2x6 to fit snug in between the upper ends, and that should do it. Unless someone can counter that with a better alternative.

I'll do a re-draw on the drawing later.

[glenn kangiser]

The longest brace you can use will be the most effective leverage wise, all other things being the same ie: similar brace types.

[Don_P]

The best brace is a wall...
I've modified your drawing to what I was thinking MD;


One thinking problem most of us have when assuming the soil is bracing the pier is that we assume the girder is one end of the lever, the point of rotation is at the surface and the other end of the lever is the footing. We're visual creatures. The point of rotation is actually somewhere below the surface, depending on soil type.

[MountainDon]

That locks up nice..

[Don_P]

Came across a pic I had online. Here's some bracing in the shop;