Need Info. On Attaching Wood To Concrete
Woodman880
| Posted in General Discussion on
I have to attach a 2 x 6 board to an old, poured concrete wall (not concrete blocks) to support some stairs. Do they make anchors similar to the type used in drywall for concrete? In other words should I drill holes into the concrete and then run bolts through the 2 x 6 into the anchors? Any thoughts would be appreciated.
Replies
Yes such anchors are available in a number of varieties, any decent hardware store, and even the big box stores will have plenty to chose among. Remember, that wood attached to concrete should be pressure treated, and if this is an exterior application it should be held away a bit (washers, or other spacers) to allow for the wood to dry.
If the wood is going to be inside, why should it be pressure treated?
This is an opinion, not necessarily based on empirical construction knowledge.
If you fasten a board against a concrete surface, the small gap between the board and the wall has the opportunity to collect moisture and/or become a haven for bugs and rot. That is why I would use treated. To your original question, I've used wedge anchors in poured concrete in the past; they worked a lot better than I thought.
http://www.concretefasteners.com/anchors-fasteners/thunderstud-wedge/index.htm
I would qualify that caution as not always being true, though there are lots of locations that building codes do require to have decay resistant lumber. One place would be : ...other framing members attached directly to the interior of exterior masionry walls or concrete walls below grade except where an approved vapor retarder is applied between the wall and the...framing members. IRC R319.1.7. So, this wouldn't be all interior locations, but it would include the interior side of concrete basement walls, a common location.
In this case I'm not concerned about building codes but I do want it to stand the test of time, so I will use pressure treated wood. Thanks.
You are not telling us what the 2x6 is for is it internal ,external what is it holding up if anything simply not an enough information.
Regards from OZ
You can make it fool proof but not idiot proof
There are a couple of ways to do it. You can either drill and set anchors and then use bolts to anchor the wood to the concrete. This is the way that a header is attached when building a deck and there will be a susstantial load on it. Or another wya is to drill and use a pecial screw called a Tapcon. It is a screw that is used to go directly into concrete. A hole is drilled with the proper sized drill bit then the screw is put directly into the concrete. This system is usually used when putting up walls in a basement , as an example, or where there will not be a large side force.
I'am not a big fan of the tapcons, I prefer the wedge bolt anchors or the old "Star" brand lead anchors.
Work Safe, Count to 10 when your done for the day !!
Bruce S.
By all means use the treated limber, but be aware that the new stuff will corrode most fasteners away in pretty short order. These being stairs, you should be sure and get fasteners that won't corrode.
Also, if you are concerned about the loading (stairs are kind of critical and all), you could look into the epoxy-based anchors. You drill a cavity of the specified size, and then permanently epoxh the anchors to the wall the same as with rock anchors.
Epoxy will hold anchors in a concrete wall?
Probably, but what I am talking about are anchors that are installed with epoxy made especially for that purpose. A good friend has installed them for a number of custmers, and some are very heavy duty for high stress applications.
You might go over to Breaktime (another forum at Taunton) and aske the builders over there what they think best also also about the epoxy rock and concrete anchors.
Joe
JUst don't use the same epoxy as they used on Boston's "Big Dig".
In this hurricane-prone area about all I see with the pros is the epoxy-based stuff. No matter how careful you are in planning a slab foundation they are bound to miss an anchor bolt or two to meet code requirements, or one ends up in a bad location. About the only method to meet code really is to drill, expoxy in a bolt, and let cure. It is a special system made just for this. Probably not worth the trouble unless you have several to do. For just a few I would use the wedge anchors. I've used a lot of Tapcons in block walls or mortar but never had much luck with solid poured concrete, also I don't think the load capacity would be as much as wedge anchors or epoxy.
And as they explained above, if it is wood contacting concrete it needs to be treated.
"Epoxy will hold anchors in a concrete wall?"Absolutely. When foundation anchor bolts for exterior walls have been omitted or misplaced, new ones can be installed by drilling a slightly oversized hole, partially filling it with bolt-setting Epoxy and inserting an allthread bolt. The resulting hold-down bolt is strong enough to pass foundation inspection.
BruceT
The strongest cost effective way to attach ACQ treated lumber to concrete is by using stainless threaded rod anchored into epoxy. I would use 5/8 rod set into a 3/4 hole. Powers Fasteners, Simpson, and Hilti all sell epoxy that can be shot out of a caulking gun. The only real way to screw up is to leave dust in the holes after drilling. Use lots of compressed air and a bottle brush to get nice clean holes prior to pumping in your glue.
I'm afraid you are wrong! There is always another way to screw up and I always figure out how to do it (ha).
I've been using Tapcon's for years. Pressure treated for a floor plate. Regular construction grade lumber for walls.
Jeff
Since this is a structural application (and not woodworking, actually), I'd advise asking the pros over at Breaktime.
I agree completely. Get advice from Breaktime.
Joe
The first question that came to mind is how strong is the concrete wall. How thick is the concrete? Is it reinforced? How old is the concrete?
I had a similar application but I was supporting a storage loft. Lots of weight and safety a prime concern. I used tapcons and plenty of exterior construction adhesive. But I also put vertical supports down the wall under the 2x6 (for me it was a 2x10 on the wall). It won't go anywhere.
If you can drill completely through the wall and use a bearing plate on the outside, it will be an even better connection. None of these methods is overly expensive. A few extra 2x's for structural integrity (bracing and columns) will give you peace of mind. Even if my tapcons fail and the construction adhesive fails, my loft ain't coming down to crush anyone.
Greg
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Exo 35:30-35
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