Surface mounting posts to concrete?

[Michael Donahue]

My girlfriend's mom has enlisted me to build her some railings for her front stairs (hard to say no and stay in her good graces! :D ). I'm just totally stumped on how to surface mount 4x4's into the existing concrete. A google search turned up contradicting answers so that's why I've come looking for help! The Simpson brackets would probably do the trick, but they'd be visible and I was hoping to avoid that.

Thanks for the tips folks!

[Chris Harry]

I havent tried this myself but was always curious if you could use a router to widdle down the dimensions of a 4x4 board so that, once the Simpson plate was installed, a standard post sleeve (vinyl, composite, etc) would slide over the post and the Simpson plate.

That might even be possible without routing down the bottom of the post, if there are sleeves that are oversized (which do probably exist).

Of course this doesnt work if you want a pure wood look.

[Paul Ryan]

Michael,

I wasa going to recomend drilling a hole in the bottom of the post and burying a long carriage bolt in the concret when you pour it so you have you pin sticking out. But then I checked and you said existing concret. You could use the plate and build some kind of molding arount them to concel them.

[Greg Sznajdruk]

http://www.ideas-for-deck-designs.com/titan-post-anchor.html

Have a look at this site.

Greg

[Brian Effinger]

Chris is right about the post sleeves. They do make them to fit over 4x4's. So I would use that and the simpson post base. Or you could just make some base moulding, like Paul suggessted. To fasten the metal plate, drill a hole in the concrete and either drive in an expansion bolt, or use an epoxy bolt.

[Brian Effinger]

Greg - I didn't see your post before I wrote mine. That is an interesting product. I have never seen them before. I took a quick look at the website and it appears to meet the intent of the building code as well. I will bookmark that site for future use. The only thing is that it may not work in Michael's situation. I saw nothing on the website about anchoring these to concrete - only wood decks. That's not to say that it won't work, only that they didn't show it and will require a little more research.

[keith ouellette]

A post seated on a simpson strong tie post seat will wobble side to side because it is designed to keep the post foot from sliding or being lifted by the structure it is attached to in a wind storm. It doesn't pull the post down tight.

Someone mentioned a lag bolt which is a good idea if done right. It can be done in existing concrete also.

There is an epoxy product made for just such a purpose. We use it here in Florida to bolt down frame walls to footers.

You drill a hole in the concrete a little larger than the lag bolt head. you can grind down the size of the head a little to cut down on the hole dia. and the amount of epoxy you use. The hole must be as close to 90 deg to the concrete as you can get. You drill a hole in the post bottom to except the bolt and mortice a hole through the side of the post meeting with the column for the bolt so you can tighten the post down tight to the ground. The hole than excepts the nut must be wide enough for a open end box wrench to fit in so the nut can be tightened.

You must clean the holes in the concrete to get the dust out. the epoxy is extremely strong. I believe it has a pull out strength in the thousands of pounds range.

[Cliff Rohrabacher]

Whatever you do: Use a penetrating epoxy on the end grain that'll be closest to the concrete.

This will prevent water from flowing up the end grain and causing rot.

[Rick Lucrezi]

Michael,

I was going to recommend drilling a hole in the bottom of the post and burying a long carriage bolt in the concrete when you pour it so you have you pin sticking out. But then I checked and you said existing concrete. You could use the plate and build some kind of molding arount them to concel them.

This is the method I always use. ( I build houses for a living) I drill a hole in the post (1/2 inch for 4x4 and 3/4 for 6x6) If the concrete is already there you can oversize the hole in the post because an accurate hole in concrete is hard to do, then I epoxy a piece of all thread in the hole. I all so put three nuts and a flat washer between the post and concrete which gives me space to keep the wood off the concrete and allows for adjusting the post height to perfection and to accommodate for future settling. When pouring your own concrete, the post can be mounted in place and I use a finish gun to attach cross bracing, this way the post is exactly where you want it and you can easily fill the nail holes. Belive it or not, when I build large post and beam style structures I use a 2.5 inch finish nail and stitch the thing together, then I can easily rack it and then I use bridge washers and through bolt every thing.

[Chris Harry]

Yeah, Simpson makes the epoxy that you can use to drive the lag into the concrete. HD and Lowes actually carry it, usually located with the other Simpson products. It aint cheap, but its a good product (I think you can buy the Sikaflex version over by the concrete products at Lowes and HD as well, but the Simpson stuff is a little less expensive and pretty much made for the Simpson products)

In fact I used the Simpson epoxy along with a Simpson 4x4 bracket to secure the bracket to my recently poured patio. I didnt have to cover the brackets on those posts (will have some sort of lattice work covering the support frame), but had planned on using post sleeves if I wasnt able to hide the posts where I wanted.

[Scott Loven]

http://www.ideas-for-deck-designs.com/titan-post-anchor.html

Have a look at this site.

Greg
Works on concrete also
http://www.ideas-for-deck-designs.com/installing-concrete.html

Scott

[Jim Galvin]

It would be nice to find out how thick the concrete is before planning this because if the concrete is not thick you won't get the embedment needed to develop the strength.

Jim