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How to secure a new building to an old concrete slab?

Z

Zachary Hoyt

Well-known Member
I am planing to build a small sugar house to contain our 2x4 evaporator and I am hoping to build it on an existing 8.5'x12.5' concrete slab that I was told used to be an apple packing sheed back when the area was an orchard. The slab has some anchor bolts but they are very rusty and have been mashed over flat to the concrete. I am wondering if there is a way to anchor the bottom of the walls to the slab or if I should just trust in gravity. The slab is six inches or so above the dirt, and the dirt slopes away all around it, so I can run the siding boards down over the slab an inch or two to keep out the wind. Any advice will be much appreciated.
Zach
 
If the old anchors won't work, then cut them off, and use new ones a few inches over. You can build the shed, then drill through the sill, and down into the concrete. Then use the expanding type anchors.
 
There are anchor kits where you drill a hole in the concrete and either use an expanding anchor or a epoxy mix and all thread rod.
 
You'll need a hammer drill and masonry bit to drill holes in the concrete- good ones are expensive, so best to just rent one. Get the fasteners first (Home Depot has many), so you'll know what size bit to get when you rent the drill.
 
Mansonary bit, yes, but not a hammer drill. I use may DeWalt 1/2" drill.
Bits can be had at just about any hardware store for under $10.
 
The anchor bolts others have mentioned are probably best option.

But, if that's not feasible, look into some straps at the side (Simpson Hardware has a good reference site). They're usually called hurricane straps. You may need more, but may be able to fasten with PAF's instead of drilling of with a smaller fastener = easier to drill sometimes. This again may not be the best/preferred option, but look at how you are building the shed and the risks. Failure would happen at the weakest connection, so if that happens to be your rafter to wall connection, then it will go before the sill to concrete.
So... look at all your connections and see what risk you're willing to take vs drilling.

Also, typical spacing around here for anchor bolts on residential is 24" o.c. That may be overkill for you.

Good Luck

Tony
 
We didn't know the column location when we poured the slab so we used a rotary hammer and epoxied threaded rod into the shops slab. On stick frames going on top of existing slabs I've used powder driven nails, concrete screws, expansion anchors, undercut anchers etc but they are never as good as cast in place. Its also a pain using them near the edge of a cured slab as you can get breakout.

I'd try to straighten the existing stuff and use it or cut and reweld some rod onto them.
 
Maybe a 1/2" drill is heavy enough to make it work, but we've got some pretty hard rocks in the concrete here, and if you hit one with a 3/8 drill, you just sit and spin. If I was going to drill a dozen holes to secure a building, a hammer drill would sure save a lot of frustration.
 
After installing new canopies at gas stations in several states I came to depend on redhead bolts and anchors. Never had a failure. Use an impact drill to bore the Right size hole, Clean the hole by blowing air thru a small copper pipe, insert the bolt with anchor and tighten slowly.
 
We did what henry0 suggested, but we dropped an epoxy capsule after cleaning the drilled holes then installed the anchors and drove them into the epoxy capsule. None them ever came loose. We were anchoring a big bed plate down for vibration equipment. Thiry years later they're still in use. Hal
 
HAmmer drill... make holes where needed and set new anchors. You can also try a ramset... but that could be rather debatable in old concrete.

Rod
 
Agreed.

You can make a good 1/2 drill work, and if all you are going to do is a couple holes you can get by. But a hammer drill makes the job so much easier and faster. I think the bits last a lot long using a hammer drill too.
 
Hammer drill and anchor bolts are the best and cheapest way to go. Back when I worked at Tracker Marine we did thing that way when we installed a new piece of equipment that had to be bolts down to the floor. Some of those machines where big heavy presses and shears that if not bolted down would have walked all over the place
 
You have hit my area of expertise as I design concrete structures for a living.

I would not suggest the expansion type anchors commonly referred to as red-heads. Everything has to be perfect to ensure a tight fit to uphold the maximum tensions that the chart suggest and have seen many of them pull out or work loose over time. Unless you really know what you are doing, I suggest you use a 2 part epoxy system. You can purchase a stick of standard threaded rod for your application. Follow the epoxy hole size and depth requirements and most importantly blow the hole clean of any dust. You will only need 4 anchors, but you might want to install a few more for peace of mind and to distribute any forces all along the sill plate instead of isolating it.

We purchase all our epoxy systems from Fastenal. They have better tension results over something from a local hardware store.
 
Lyle, if you are talking powder actuated fasteners, NO, do not use for structural connections ever, they do not achieve the values needed, that say a sleeve anchor, wedge bolt, expansion bolt or epoxy anchors will provide.

Epoxy anchors are great when the fastener hole edge distance to edge of slab or similar is minimal, where an expansion type mechanical fastener may fracture, spall or fail prematurely because it cannot achieve the pull out or shear value because its too close to an edge, thats when epoxy anchors shine LOL!

In a situation like this, the fastener is only as good as the existing concrete, if the concrete has achieved its design, or you know its say 3000 psi, or 4000 psi, you can determine the shear, pull out values etc. of proposed fasteners and decide from there. Technically, you could go to a Hilti Catalog, make a selection and its plausible that the strengths you need are adequate. Even with doing the above, if it was for anything structural, more so an occupied or will be occupied building, an engineer should check, calculate and or confirm the connection/details are sufficient.

Powder actuated fasteners might be ok to fasten metal stud track to concrete, steel, possibly ok to hang ceiling tile grids, but even the latter depending on loads would not be acceptable.
 
I have to chuckle at some of the answers.
Those folks looking for optimum or premimum holding power seem to forget that you are bolting down a piece of wood. Even a simple to use quick bolt would be more than adequate for a 2x4 or 2x6 bottom plate.
Why use a 6,000 lb rated fastener on wood that can only withstand 1200 lbs of force??
Take a look at a garage or house that has been damaged by a storm or hit by an automobile and it is ALWAYS the wood that gives way no matter what kind of fastener was used.
And you want to use a Good hammer drill.
Rent one if need be. None of this stuff with a 1/2' drill and hardware store grade bit. Arrrgh!
I lay the wood down and drill right through it into the concrete. Perfect placement every time.
3/8" bit and 3/8" quick bolts. Takes less than half a minute to drill each hole.

100_09621.jpg


05-7240.jpg
 
No, NEVER use powder actuated (Ramset) for this, well I realize its not a highly critical connection with a heavy loading, powder actuated will never achieve strong values, you can readily see it in Hilti's charts within their catalog.

Only reason I mention it is I don't want anyone to think these are acceptable to use for any structural connection.
 
(quoted from post at 18:03:49 10/11/12) Lyle, if you are talking powder actuated fasteners, NO, do not use for structural connections ever, they do not achieve the values needed, that say a sleeve anchor, wedge bolt, expansion bolt or epoxy anchors will provide.

Epoxy anchors are great when the fastener hole edge distance to edge of slab or similar is minimal, where an expansion type mechanical fastener may fracture, spall or fail prematurely because it cannot achieve the pull out or shear value because its too close to an edge, thats when epoxy anchors shine LOL!

In a situation like this, the fastener is only as good as the existing concrete, if the concrete has achieved its design, or you know its say 3000 psi, or 4000 psi, you can determine the shear, pull out values etc. of proposed fasteners and decide from there. Technically, you could go to a Hilti Catalog, make a selection and its plausible that the strengths you need are adequate. Even with doing the above, if it was for anything structural, more so an occupied or will be occupied building, an engineer should check, calculate and or confirm the connection/details are sufficient.

Powder actuated fasteners might be ok to fasten metal stud track to concrete, steel, possibly ok to hang ceiling tile grids, but even the latter depending on loads would not be acceptable.
Click to expand...
K, I know what you are saying, in this application I thought it would be fine, after all he was considering just sitting it on the slab, right?
 
Hey Zach
Just a little food for thought.
When ever I build small out buildings I always put a floor and skids under them. That way if you ever decide to sell or move it, its easy to do
 
Being on an elevated slab makes it easy. Drill holes THROUGH the slab. Use any steel you have around to use as "washers" and use threaded rod through the slab to anchor the sole plate. Any type of "expansion" anchor is likely to split the edge off of the slab.

JMHO

Areo
 
Since, like it has been mentioned, you aren't building a skyscraper - for the 6 or 8 anchors you need, just get the expanding anchors, a 1/2 drill, and a proper size masonary bit at the hardware store. Anything else is just wasting money.
 
They sell a 5/16 drive in pregnant nail type of anchor that would be fine for a shed. You just drill the 5/16 holes through the plate into the slab and drive them in. They work really well and you don't need a wrench.
 
Have you ever heard of these?

http://www.concretefasteners.com/anchors-fasteners/tapcon-screw/pricing.aspx?gclid=CKaxraaf-rICFUGK4AodZVUA3g

Tapcon fasteners.
Drill with regular drill or hammer drill, screw in through plate into concrete. Simiple, quick, not terribly expensive.
 
Silly me!

I thought I was doing good work drilling those thousands of holes for anchors with my Milwaukee 1/2 inch magnum hammer drill.

I know now that all the cool contracting dudes have those $600 Hilti sds drills. Looked at one recently at the 'lectric supply and boy it sure was pretty, a product of the Chinese working man!

I hung my head and was ashamed of my 20 year old (fully functional) American Made drill cowering in its metal box.

:)

Brad
 
Wedge bolts will work fine but if your concrete is sketchy or you are unlucky, you will kick yourself for not just doing it right and getting a tube of epoxy. Wedge bolts can be a problem with concrete that is not perfect and they can also cause problems by just slipping if you are unlucky, its just the nature of the beast.

Tapcons work but you gotta put in more so do you gain anything in that case? You probably already have some at home though.

Rent a Hilti? If you want to go that route you will have more money in gas going to get it and returning it than if you just buy a single shot next time you are in town. You dont want to go that route though, I would rather use tie wire in the hole with a spike. Just too many failures and blowouts with a Hilti in older concrete.

Wedge bolts - 50 cents each. Buy extra for when they fail.
Tube of epoxy and threaded rod - 30 bucks. Clean the hole and nothing will fail.
 
(quoted from post at 20:40:23 10/11/12) Silly me!

I thought I was doing good work drilling those thousands of holes for anchors with my Milwaukee 1/2 inch magnum hammer drill.

I know now that all the cool contracting dudes have those $600 Hilti sds drills. Looked at one recently at the 'lectric supply and boy it sure was pretty, a product of the Chinese working man!

I hung my head and was ashamed of my 20 year old (fully functional) American Made drill cowering in its metal box.

:)

Brad
Click to expand...

You must not use a hammer drill too much, some WEEKS we put in that many holes.

20 year old hammer drill? Surely you jest....
 
Aren't you guys that mentioned using the expanding type anchors concerned about using them at the edge of the slab?

I'm not in construction, but it seems to me that using any kind of expanding anchor or hammering concrete nails in close to the edge of the slab, could crack or break off a piece of concrete. :shock:
 
I also have a Milwaukee hammer drill for small stuff.
It has been a good drill and I use it more than the Hilti.
It doesn't even start to compare with the Hilti though - not even close.
I was doing some work at an envelope factory and the maintenance man there had gotten a DUI and needed some dough to pay his fines and court costs.
I gave him $200 for the Hilti. It had been used very little.

100_09761.jpg
 
(quoted from post at 22:23:35 10/11/12) Aren't you guys that mentioned using the expanding type anchors concerned about using them at the edge of the slab?

I'm not in construction, but it seems to me that using any kind of expanding anchor or hammering concrete nails in close to the edge of the slab, could crack or break off a piece of concrete. :shock:
Click to expand...

Not worried, no, but it can happen. If it does happen, move over and drill a new hole, patch the old one and move on with life. Just slowing down your drilling speed can make a world of difference in a sketchy spot but think about it, do you really want to work at drilling a bad spot in concrete to put in a bolt that is suspose to hold your building together? If you are drilling and hear or feel it going bad, just pick a new spot and be done with it.
 
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