Gilles' Outlet

August 8, 2009

Repairing a Second Story Deck Piers

Filed under: Decks — Gilles @ 6:20 am

A second story deck is about to fall. We jacked it up, pour new concrete piers and install bracing.

 

Skill Level: 3~4 (Intermediate ~ Advanced)

Time Taken: About 8 hours

This article is about structural repairs on a second story deck. Structural repairs should always be performed according to local building codes by qualified professionals. Be sure to obtain the necessary permits before any project. Incorrectly performing structural repairs can lead to structure failure, property damage and possibly causing fatal injuries to people or animals.

This article is for entertainment only. Do not attempt to duplicate any of Gilles’ Outlet techniques, methods or approaches. If you decide to ignore this warning, then you do so at your own risk. In no way will the publishers of this web site be held liable for any injuries or damages, direct or consequential, incurred by any person who attempts to follow the examples shown herein.

This second story deck looked fine from far away but upon more careful inspection, there is something not quite right with its footings. The right footing does not appear to be resting flat on the ground.

While walking on the deck, I noticed that the right side on the picture was significantly lower than the left side, almost 4’’. The whole structure appeared to no longer be level and plumb.

The plan is to replace those pre-cast footings by concrete piers, poured in place. Metal connectors will be precisely located in fresh concrete and posts will be attached to them. Finally, in this area, building code requires second story decks to be braced and this deck is not. This will be a good time to install them.

There were a few plants stored on the deck. They were invited to leave.

Left: Upon closer inspection, the pre-cast concrete pier appeared to dangerously lean on one side. It is just like if it was installed directly on disturbed, non compacted soil and eventually sank. Water erosion may also have contributed  to this situation.

 

Right: An even closer inspection reveals how dire the problem is: the concrete pier moved so much that the  metal rod connecting the pier to the post is bent. Critical parts of the connector are badly corroded. The connector could break at any time and send the whole deck crashing down.

The structure needs to  be supported during the pier repair. I will need to jack the deck, remove the existing post, perform the repair as the deck is jacked. This is a potentially dangerous procedure.

Left: I pried all nails attaching the left post to the 4×6 beam. This way, I will not be hammering nails when the structured is jacked, reducing chances to de-stabilize it.

 

Right: I estimated the load on the post to be around 1200lbs. When jacking structures, experience has taught me to spread the load on the ground: I laid a piece of scrap 2×10  close to the left post. I cut a piece of 4×4 to length and connected it to the beam with a metal connector and 10d nails. This will avoid the post from moving as the structure is jacked.

I installed an 8 ton jack under the post. It is overkill but it has a larger base and therefore is more stable.

Left: I pumped the jack. The structured started to move. I made sure I jacked up slowly, listening to the structure. Wood makes cracking noises before breaking and these would be my warning signs to immediately abort the operation.

 

Right: A few minutes later, all the load was transferred from the old post to the temporary support, through the jack. The old post swung free. I removed it. I was very careful to spend the least amount of time under the jacked structure.

Left: The pre-cast pier did sink in the ground about 3 in deep. This suggested that there was no proper footing under this pier. So I prepared to pour a real footing: a 12×12 x12 concrete pad will be just fine for this application in this region where the frost line is 12’’.

I marked the position of the footing using white spray paint. I started to dig and ….

 

 

Right:… I reached pay dirt so to speak. There was in fact an existing footing with the remains of a metal connector in its center. The footing was buried under about 4 in of top soil.

Well, when doing home repairs, nothing ever goes as planned. Time for a change in plan: I will be pouring a new concrete pier and connect it to the existing footing with #5 rebar.

Left: When connecting a new pier to the existing footing, it is typical to drill 1/2’’ in the concrete and drive in #5 pieces of rebar. Sometimes, rebars are also set in epoxy to further enhance the bond.

 

Right: I will be using Simpson Strong Tie brand epoxy for this.

The manufacturer instructions demand holes are cleaned with compressed air at 80 psi for at least 10 seconds.

Left: Then, holes need to be cleaned with a special brush  4 times. After brushing the holes, the manufacturer demands holes are cleaned one more time with compressed air.

 

Right: This brand of epoxy is dispensed out of a tube similar to caulking. Pushing the material out mixes the epoxy and dispenses it into the holes through a flexible hose. The manufacturer recommends verifying that the epoxy is properly mixed when dispensing. When properly mixed,  it has a light grey color.

Left: I immediately drove #5 rebar in holes. It was a very tight fit, which is a good thing. Overall, this little pier ended up having three pieces of #5 rebar. Rebar was installed so they were all at least 3’’ from any edge of concrete.

 

Right: I cut a piece of 2ft long quick tube, diameter 8’’. This will contain the concrete for the pier and it will dry in a cylindrical shape.

Left: I need to precisely center the pier under the existing beam. I first made sure that the beam was absolutely level. I then determined the center of the post and drove a nail in the beam. This allows me to attach a plumb bob. Now, I just need to place the center of the quick tube at the location indicated by the plumb bob …

Right:  … like this. It is difficult to see on this picture but this is actually the right location.

Left: Once the quick tube was precisely located, I built a set of braces with scrap lumber. This will prevent the tube from moving as the concrete is poured.

 

Right: I mixed about half a bag of concrete mix and started to pour in the form. The concrete needs to be wet enough but not too wet. The more wet the concrete is, the weaker it will cure.

Left: It took about a minute to fill the tube. I used a margin trowel to form a little dome at the top of the pier. This will promote drainage and lead water to the sides of the pier instead of keeping it in contact with the post. This significantly increases the life span of the wooden post.

 

Right: I precisely located a  Simpson Strong Tie Post Base metal connector in fresh concrete. Again, I used the plumb bob to align the center of the connector and I made sure the connector was set level and plumb on all axis.

Now, the concrete needs to cure for at least 24 hours to make sure it will have enough strength to handle the load. During this period, I made sure the concrete stayed wet. This is called “wet curing”.

Left: With the beam still perfectly plumb and level, I measured the distance between the bottom of the bracket and the beam. Since I am going to use a metal bracket, I removed 1/16’’ to account for the thickness of the bracket and cut a new piece of pressure treated 4×4.

 

Right: I installed the new post and placed a hot dipped galvanized Simpson Strong Tie Post Cap. Notice that it is not yet fastened.

Left: I slowly lowered the jack to transfer the load back to the new post. Eventually, the jack lowered to its maximum and the structure started to bear only on the new pier / post.  I checked the post and the structure for level and plumb one last time. Since everything was right on, I moved on to the next step.

 

Right: I fastened the post to the base connector using 16d hot dipped galvanized nails. I first installed 4 nails (two on each sides).

Left: I turned my attention to the post cap. I installed three 16d hot dipped galvanized nails on each face, according to the manufacturer instructions. 

 

Right: I finished nailing the post to the base connector. The two big large holes are for manufacturing purposes and are not to be used to install nail or screws.

I repeated the same procedure for the other post. At this point, I let the concrete piers cure for about 8 days. Because it was very hot and dry, I made sure to spray water on both piers twice a day. I also covered the top of both piers with 6 mil plastic sheeting to reduce water evaporation.

At this point, the deck was now level and plumb. Bracing still needs to be installed.

Left: The bracing starts by cutting four pieces of pressure treated 4×4. Building codes have some precise requirements on those: they must be installed at a 45 degrees at the beam and the post. They also need to be fastened at least 18’’ away from the post top.

Cutting these braces is actually quite tricky: 4×4 posts are never really straight so those two cuts are actually compound cuts. Anyone who makes a mistake cutting these is automatically forgiven. Cut those longer, measure angles precisely and cut them step by step, removing a little bit of material at a time.

Right: I drilled a countersunk hole on each side of every brace.

Left: Braces will be fastened using 1/2’’ lag screws with washer. This hardware needs to be hot dipped galvanized because it will be exposed to elements and pressure treated wood.

 

Right: The lag screw and washer will sit flat, recessed in the countersunk hole. This is important for the lag screw to be effective when installed on an angle piece like this brace.

Left: I pre-drilled the beam where the new lag screw will be installed. This is necessary with large lag screws or the wood will most certainly split.

 

Right: I pre-drilled the post as well.

Left: The brace was installed. I fastened lag screws tight with a large 1/2’’ drive ratcheting wrench.

 

Right: I repeated the operation on the second side of the first post. The bracing is now completed on one side of the deck.

Left: The lag screw sits recessed in the countersunk hole. I expect this connection will look better and better as the wood weathers to a darker color.

You can see the manifestation of the compound cut: the intersection between the brace and the post tips ever so slightly down to the right side.

 

Right: After a few more days, I peeled away the quick tube. It came off very easily.

Left: After peeling the quick tube, the edge of the footing was slightly sharp. I used a brick hammer to round it up. In insight, I could have done this when the concrete was still wet, by rounding it over with a special masonry tool. Alas, I do not own such a tool. This worked well.

 

Right: I back filled around the new piers with top soil. I also compacted it with a hand compacter. This will help fight erosion.

The finished project. I do like the look of the new piers in concrete. If I did not want so much concrete to stick of the ground, I could have cast shorter piers. I could also dress the piers build building wooden boxes to hide them.

Tools Used:

  • Brick Hammer
  • Pry Bar
  • Margin Trowel, Brick joint trowel
  • Water Sprayer
  • Ratcheting Wrench
  • Hammer
  • Power Miter Saw
  • Shovel
  • Cordless Drill
  • 8 Ton Hydraulic Jack
  • Air Compressor
  • Caulk Gun
  • Plumb Bob
  • Level
  • Tape Measure

Materials Used:

  • Simpson Strong Tie Epoxy – One tube 
  • Simpson Strong Tie Post Base – 2
  • Simpson String Tie Post Cap – 2
  • Concrete Mix – 5000psi Concrete – 1 80lbs bag
  • 4×4 Pressure Treated Post
  • Lag Screws + Washer – 8
  • Rebar #5 – Approximately 5ft

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