After the structural engineer pointed out the need for additional hold downs we needed to figure out exactly what to do. The panel manufacturers opinion was that they have no responsibility for how the panels interface with the rest of the building and the structural engineers opinion was that they know what is required and it was not part of his work.
In the end Insulspans engineer provided us with a plan for hold downs. On the plan they consisted of 54″ long pieces of “CS-16″ coil strap.
Simpson CS16 coil strap
The plan from the engineer called for the use of gunpowder setting of the nails whenever connected to concrete. In my experience, trying to attach this using my Ramset gun with nails 2″ on center would have proved near impossible. The concrete would have spalled to pieces trying to get the nails in so close.
My alternative would consist of using a concrete drill and hammered concrete nails. For this purpose I purchased a Bosch rotary hammer. Strangely enough it proved impossible for me to find nails that were large enough to be used with the smallest drill bit available.
After much searching it was decided to use concrete screws instead. Screws tend to not have the same shear strength as nails, but the engineer OK’d the substitution.
These straps ties the panels down to the foundation, but there were still places where there are panels stacked on panel. These still needed to be tied down as well. However because the only lumber in many of the panels are in the seams, these were the spots where the hold downs would have to be. However the seams don’t necessarily line up, so we had to have custom steel plates made.
I stopped by a local metal fabricator for a price for five 16ga. 48″x12″ steel plates. They did not have 16 gauge steel in stock at the time, so I went with 12 gauge. Even thicker than called for. The cost came to about $160.
At the house we used a drill press to make the holes necessary for fastening the plates to the walls.
Fabricating plates
The actual installation of the plates only took a couple of hours.
Plates installed
It was clear that Insulspans engineer was unaware of the situation in the field because he specified a connection which would require me to dig out the backfill, cut the sewer line and compromise the dampproofing to install the straps.
After inquiring with the structural engineer he suggested I open up the panels on the interior to expose the lumber splines and use post connectors anchored into the concrete.
Simpson DTT2Z post connector
HOW TO PERFORM POST-ASSEMBLY INSTALLATION OF HURRICANE AND SEISMIC HOLDDOWNS IN A STRUCTURAL INSULATED PANEL.
1. Collect the necessary tools and supplies.
You will need tools to cut open a section of panel, drill into the concrete, attach the hold down to the concrete and the lumber.
I had to make the choice of whether to tear open enough panel to fit in a rotary hammer with a 12″ long bit on it, or find a right-angle chuck.
The local tool stores or lumber suppliers wanted $200 plus two or more weeks for delivery. I ended up purchasing it online for less and received it two days later.
The connectors were a special order from Simpson and took almost a week to arrive.
2. Use a drill to provide a starting point for cutting.
Measure out how big the cutout needs to be. In my case the vertical height was governed by the height of the rotary hammer and the width defined by the size of my impact drill with bit and screw.
I first attempted to use a regular hole saw, but it was just burning the OSB. I recalled I had a 1-1/2″ auger bit I purchased for use when cutting access to the wire chases and it worked much better.
3. Cut open the panel.
Using the drilled hole as a starter I used a hand saw to cut open the panels. The handle of the cheap saw snapped in half and I used the reciprocating saw for the rest of the cuts.
4. Open panel and remove insulation foam
The OSB sheet will pop off easy after cutting around it.
To remove the insulation I made a couple of horizontal and vertical cuts through the foam. This allowed me to remove it in fairly large chunks. Making it easy to piece it together again. Unfortunately I did not mark the pieces as I removed them but we were able to piece it together anyway.
5. Drill hole in concrete for the anchor
I did wonder how well it would work to drill a deep 5/8″ hole through the concrete using a right angle chuck and a relatively small rotary hammer.
It took some effort and quite a bit of heat was generated. But with occasional cooling off of the bit/chuck and removal of the dust using a vacuum it was possible to drill the hole as deep as necessary.
7. Cut threaded rod to length
At first I used my hacksaw until I realised the blade was dull. I switched to the reciprocating saw again. I eyeballed the length and it of was a little bit longer than needed.
8. Anchor threaded rod with adhesive
Using an acrylic adhesive ($25 per 10 oz. tube) we filled the hole about half-way and inserted the threaded rod. The acrylic will set in about 30 minutes.
9. Fasten post anchor using a washer, nut and 2-1/2″ Strongdrive screws
The post anchors came with screws included, but unfortunately were not of the size the engineer suggested so I had to purchase additional screws.
A lesson I learned was to screw the nuts on the threaded rod before cutting. I spent 15 minutes on my knees trying to thread the nut through the cut threads on the rod.
The impact driver is probably the tool I have used the most so far. I might never drive a screw with a drill again.
10. Finish.
Before I seal the up the panels again the engineer will inspect and approve.
In other things I have received the homeowners electrical permit allowing me to get started on the electrical installation.
In the mean time we have had our heat pump delivered and the duct work and HRV will be installed during the week.
In an upcoming post I will go more into the mechanical systems as well as energy efficiency.