I need to add additional straps or anchor bolts to attach the 2×4 sill plate to a block wall. The top course of the wall is a 4 in. high solid block. Does any one make something special for this or can I used standard 1/2 in. anchor bolts.
Discussion Forum
Discussion Forum
Up Next
Video Shorts
Featured Story
Fine Homebuilding is excited to be the official media partner of the 2024 Building Science Symposium series! This event offers builders, tradesmen, architects, designers and suppliers to discuss topics ranging…
Featured Video
SawStop's Portable Tablesaw is Bigger and Better Than BeforeHighlights
"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.
Replies
I would use 7" redcap expansion bolts or equivalent. Put them in deep enough so that about 3/4" is protrudes above the treated 2X4 to accommodate the washer and nut. Let the hammer drill or the rotary hammer do the work. You can drill right through the wood and into the concrete. When the hole is completed, use air to blow out the concrete dust. Place the washer and a nut on the bolt with the nut just about one thread above the top of the bolt. Tap the bolt until it bottoms out and tighten. This method ensures the washer is in place in case the head mushrooms, which would make it difficult to get the washer on.
If you install the bolt before the plate, place the two nuts on the end of the bolt so that the upper nut is just about one thread above the end of the bolt. Tighten the nuts together and then gently tap the bolt into the hole until it bottoms out. Give it a good smack - not too hard. Remove the nuts and instal the plate. This method prevents mushrooming of the bolt, which makes it hard to tighten the assembly as it may rotate in the hole.
With expansion anchors in concrete block you risk splitting the block. Epoxy anchors would be a better choice. You have to be careful you don't drill a hole all the way through into a hollow in the block below and loose all your epoxy down the hole.
You could drill so the hole lines up above a web in the block below if your framing layout permits. That will keep your epoxy in place.
Such an arrangement will be sufficient to anchor a wall in normal circumstances. But, if you have high wind loads or seismic loads, you risk breaking the top block off the wall despite how secure the anchor is embedded in the block. If you need to resist high winds or earthquakes, you'll need engineering help to design a proper anchoring system.
Good point. I usually think of the top row of blocks to have a solid beam poured within, along with rebar, from my Florida memories. The corner blocks and certain other blocks are tied in with rebar and concrete too. If a strong wind pulls the walls up enough to rip off the top row of block, then there is a good chance that it would rip it off with j-bolts installed too.
Normally, I would expect a tornado or microburst to pull off the roof first and then put more of a lateral pressure on walls. If the roof holds, I don't see the house being that vulnerable. The next storm might prove me wrong.Les Barrett Quality Construction