# Poor Deck Post Anchors



## Schnelltdi (Apr 2, 2008)

I was wondering if anyone knew if there isn't anything better than the simpson and usp deck post anchors which are attached to concrete? These are quite thin and seemingly not rigid. Why doesn't anyone make one like this: A square plate with 4 holes on the outside corners, a square tube welded to the middle of the plate, holes for through bolting the post inside the tube, all material made of 3/16 - 1/4 inch steel, and either hot dipped galvanized, or made of stainless steel. Four J bolts would be sunk into the concrete pillar when poured! Now that would be a proper post anchor wouldn't it? Does anyone know if sucha thing exists??? If so, who sells it???


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## concretemasonry (Oct 10, 2006)

What kind of loads are you trying to get the connector to resist?

A typical connector is designed to hold the post in place to transmit the vertical loads into the concrete foundation. It is also intended to resist the horizontal shear loads at the top of the concrete/bottom of the post.

It sound like you want a bracket to hold the vertical post rigidly so it will act like a very strong telephone pole continuous with the concrete. This would need to resists moments. With the limited area you have on a concrete base and the small size of a post, you cannot develop much resistance with nails, or bolts. The posts should be braced or the deck should be braced in two diections.

Remember, wood shrinks and holes enlarge, so wood structures are very weak without bracing.


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## Schnelltdi (Apr 2, 2008)

So how does the conventional type of post anchor connector resist moment when they too are (when finally installed) tightened to the concrete and the post rigidly utilizing bolts? Is it the "give" or flexibility provided by the the connector/ base such as Simpson/ USP etc?

The purpose is not to make it rigid like a telephone pole, but just not so thin, and to resist lift etc. So many decks are poorly made. They wiggle when you have any amount of people walking on them. They sag not long after being built etc. etc. I just prefer to make it as good as can be within reason. Strangely enough, it usually doesn't cost that much more to do so.

Michael


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## concretemasonry (Oct 10, 2006)

You do not resist a moment using a typical connection. Don't you think they would have on available to work within the space you have available.

Any time you are attaching a flimsy material, like a wood post, to a rigid foundation, you width and length and a lot of connectors since wood will never be as good as it is when it is first installed. Nails work loose and wood shrinks. - Ever seen a new PT deck shrink?

The existing connections do not cause the wiggle and flimsiness. The wood materials, design and bracing of the deck does that.

Full bay bracking in two directionss is the best. Short diagonals between posts and beams help some, but are not as good.

Diagonal decking helps with rigidity. Diagonal straps under the deck can also help.

Tieing it to the house at two points is good, but you must find a way to do it and not let the house rot because of water penetration if you do not seal AND flash it correctly.


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## BuiltByMAC (Jan 31, 2008)

Schnelltdi said:


> Four J bolts would be sunk into the concrete pillar when poured! Now that would be a proper post anchor wouldn't it? Does anyone know if sucha thing exists??? If so, who sells it???


If you want such an anchor, take a diagram to your local metalsmith and have him weld some up for you. Get them powdercoated and there you go.

If you are going to go to the trouble of installing 4 J bolts for each post, why not just drop 2" or 3" square iron pipe into the wet concrete. When the concrete dries, box around the pipe with pt and wrap it with whatever material matches the deck.

Or, if you're dealing with existing concrete pad, drill holes and bolt a 3" threaded pipe flange to the concrete. Screw a 3' tall pipe into the flange and box around it w/ pt, wrap with matching material.

You can't make a wood to concrete connection at the bottom of a wood post strong enough to resist lateral force...

Here's a pic of an handrail I built using threaded pipe flanges bolted to concrete.

Mac


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## justdon (Nov 16, 2005)

I built a small porch once,braced the wood well. But I took that cheap metal stove pipe and buried it in the ground as deep as I could put like 3/8 rebar down center of it and left it stick up 3-4 inches out the top in center. I then drilled a hole in bottom of upright 4 X 4 and put one of those tin connectors on bottom of wood,,,figured (right or wrong) that the metal should keep wood more stable and be a wearing surface so to speak. So far NO wobble and I didnt want it attached to the house cause I wanted to reside it and didnt want the obstruction to interfere,,,thinking I can ALWAYS attach it down the road BUT hard to anchor to OLD concrete block anyway!!

I agree IF you want what you were saying,,,find a shop to built them in,,know anybody with a welder??Use two angles and make a box of them!!MIGHT want to drill a ton of drain holes in bottom so it isnt standing in water!! Dont think shear force at ground level is too high!!

When attaching to the floor stringers(forgot real term) use hex headed threaded bolts so you can 'wrench' both sides TIGHT(like tightening when the wood drys out) when you want to(and use LARGE washers BOTH sides,,,lots of people use those stupid carriage bolts which you can never get on ,off or tighter!! THATS where decks get wobbly in MY experience!!


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