attaching shed to existing slab
almostbluefin
| Posted in Construction Techniques on
Okay, I’m a newbie with a 1922 California craftsman and a garage that’s falling down. This winter I’m preparing to, um, “remodel an existing structure” by tearing down 90% of the garage and creating a smaller (12 x 12) shed/workspace in the spring.
Pretty much the whole backyard is paved, including the slab foundation under the current garage. I’m looking over various plans, sketching out dimensions, etc. but I can’t find anything in the books about what to do to secure a shed to an existing slab, rather than pouring a new one. I am assuming there is some nice combination of hole drilling and lag bolting I could gerry rig but does anyone have suggested techniques? Good reference books? Many thanks.
Replies
How thick is the slab???
Is drainage an issue???
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming
WOW!!! What a Ride!
either epoxy anchor bolts or expansion anchor bolts
If he has enough slab...
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming
WOW!!! What a Ride!
How much slab is enough slab? I can drill into it and check. It's sloped to the edge of the lot (which I can tell by the way rain runs through the holes in the current roof).
3 or 4" and it'd be better to epoxy the anchors in....
5 or 6"and you could use expansion bolts...
2 or 3" and it's time to find a plan "B".........
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming
WOW!!! What a Ride!
and plan B is....VELCRO!
Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations.
Your climate is probably a lot different than mine, but around here (Massachusetts) building right on a slab could be asking for trouble. To avoid problems with rot and insects, any wood should be at least 8" off the ground. But then, around here, any footings have to be 4' down to get below the frost.
Golly, life must be sweet in a place where all you had to do is lag a 2x4 to the slab and start building.
Al Mollitor, Sharon MA
so if you cannot build on a slab. How do you build a slab on grade house.
I used to live in Western Mass and I know that frost well. While I miss the seasons I'm also glad to be doing my first real home work out here in sunny CA. It still boggles my mind what kinds of things you can get away with out here (outdoor water heaters? flat roofs?).
Epoxy anchors hold better than expansion anchors, and are less likely to crack the slab if the concrete is low in strength.
You can't lay wood on the slab either. I assume you know that and didn't mention it, but I say it as intro to my suggestion. I would install one course of concrete block. Drill holes every four feet or so into the slab, clean out all the dust, and epoxy galvanized threaded rod into the holes. Make the rods long enough that they come up through the course of block and the sill plate and perform as anchor bolts for the sill. Fill the cores of the blocks that have the rod in them with concrete.
For a more solid base, use lintel block instead of standard block. Lay several lengths of rebar in concrete along the entire length of the block. Bend the rebar around the corners.
You could form up and pour a beam as well, again anchored with epoxy'd rods.
I know nothing about California codes and what might be specifically required for seismic protection, but what I've suggested seems pretty solid for an outbuilding.
you can lay PT wood on concrete,
You can't lay wood on the slab either.
Why???
'Cause of CC contact???
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming
WOW!!! What a Ride!
I guess I didn't say it as clearly as I meant to. What I mean is that it's not good practice to lay a sill plate on a flat slab, because the studs and siding will be too close to the "ground" (the slab), and will stay wet. Water won't hurt pressure treated wood, but a pressure treated sill plate sitting in a puddle will become waterlogged and transmit the water to the bottom of the studs and to the sheathing. Water hitting the slab will splash up and wet the bottom edge of the sheathing even if the face is sided with a water proof material.
It's better practice to raise the wooden structure off the slab so it's not sitting right in water puddles.
Also, water will work it's way under the sill if it's right on the slab and you'll have water in the garage. True, you can caulk, but caulking is not reliable enough for my taste.
got it....
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming
WOW!!! What a Ride!
Good thoughts, thanks. You are allowed to just build a PT sill for a shed directly on a slab here in my part of CA (with some caveats about what the shed is for). I think it's probably worth the extra effort of a block or footing foundation, though. I'll get some epoxy bolts and let you know how it goes in the spring.
Epoxy anchors provide the best in perfomance. But they require a little more attention to detail to correctly install. One anchor that wasn't mentioned is the Red Head LDT anchor. All of you out there are familiar with the little blue Tapcon concrete screw. The LDT is just a large diameter or BIG version of the Tapcon. It provides better perfomance than traditional wedge type expansion anchors and its easy to install. Check out the web link below.
http://www.ramset-redhead.com/ldt_prod01.asp
"nice combination of hole drilling and lag bolting"
Lag bolts are a poor choice for even non seismic areas. Also there are difficult, being weak, because they fail while being installed, a real nuisance. Look at a Rawl catalog or something from Simpson.