I've got an existing 10'x12' shed sitting on a 4" thick slab of slightly larger dimensions. I'd like to anchor the shed to the slab without moving or raising the shed.
The shed sits on several columns of pressure-treated 4x4's that are in mostly good shape. These 4x4's only lie beneath the shed floor and do not extend beyond the exterior wall.
See the drawing at the link below:
formatting link
I've been looking for a bracket (e.g. Simpson) that looks like the one I've drawn in the link above that can be used to anchor the ends of the 4x4's to the slab. I cannot find one of these in the Simpson catalog. Does anyone know where I can find something like this or similar?
I took a look in the SST catalog but didn't find any connectors that would slip onto a 4x4...... too small. :(
How about lagging a 4x4 "rim joist" to the ends of the existing 4x's (both ends of them) and then anchor these added "rim joists" to the slab with a simple angle bracket.
Use 1/2 lags x 8" long (6" seemed a bit short) Check out the Simpson HL Heavy Angles
I think this will be the easiest way to anchor your shed.
Why the 4x4's? I would think the concrete slab would make a much better and longer lasting floor than whatever junk flooring came with the shed?
Anchor the shed walls directly to the pad. If its made of wood it should have a 2x4 sill plate and if metal the sides should be bent inward with punched holes just for that purpose.
Drill holes, insert short sections of all thread into a mortar mix made for the purpose and bolt the sucker down to the pad.
As an alternate choice I would just buy heavy gauge wall angles and use three along each side.
If you are in a windy area use the perforated metal like garage door openers are installed with and run an strip along each wall as far as your budget allows. The same could be done along each end but you would not have a many place to attach it to the runners.
Looks like the SST HL37 angle bracket may work. I drew a new sketch of the design here:
formatting link
Questions I still have:
1) Should I use two HL37's per 4x4 end as shown in the sketch, or is one per 4x4 end sufficient?
2) If I use two anchors per 4x4 end, one on each side, should I connect them using a 1/2" bolt through the 4x4, instead of using lag screws?
3) Should I use concrete anchors in the concrete, or would a two 4" lag screws per angle bracket be adequate? In either case I'd use concrete anchoring epoxy.
4) I was planning to anchor at each corner of the shed. Is that adequate?
Other information:
The shed is a pre-fab shed with finished interior and electrical service. The flooring is 5/8" or 3/4" plywood over 4x4 pretreated "joists" that are visible underneath that lie directly upon the concrete slab, and to which I plan to attach the anchors. The 4x4s are nailed from the inside to the plywood subfloor.
The shed cannot be moved or raised! And, I cannot drill concrete anchor holes directly under the shed--not enough clearance to get a drill and bit underneath, hence the need to offset the anchor holes from their attachment to the 4x4s. I can drill horizontal holes into the 4x4s if the holes are at or near the center of the 4x4s (which means I may not be able to drill straight through holes to attach the HL37 anchors to both sides of a 4x4 and may have to use lag screws into the wood, even if I anchor both sides).
The shed is located in the San Francisco Bay Area, so my primary concern is the shed sliding or being thrown off the slab due to earthquake.
It's a shed. Drill straight down through interior floor and 4x4, squirt some of the fancy epoxy down there, and screw in big lag bolts, with a big washer or spreader plate on top so the bolt doesn't go through floor. Threaded rod pounded in with a mallet, and big nuts on top, would make it removable. Won't look any worse than toe-stubbers out in the weather. And if you pick you spots carefully, it won't interfere with the usability of the shed. One in each corner, tucked right against the walls, should be plenty.
As to earthquake protection- unless you are near the edge of a cliff where the shed could slide over, tying it down hard to the slab will likely INCREASE the damage in a quake. Instead of just bouncing around as a unit, any ground flex will be transmitted to the structure of the shed.
Upon reading aemeijers' suggestion, I'm inclined to agree with his suggestion.
I think my original suggestion is a superior design but as aemeijers says "it's just a shed". And how much capacity do you really need?
Are we talking wind or earthquake restraint?
As aemeijers says....tying the shed down will transfer more load to it. Yeah, after you're done.....the 4x4 are tied down. What's the rest of the load path like?
Connection from the 4x4's to the shed sill & walls? Shear capacity of the walls? Plywood? Wood sheathing? MDF crap siding?
The whole shed doesn't weigh much (less than 2000lbs) so you don't need much anchorage.
Simply your life....either use aemeijers' suggestion or my 4x4 (or 2x4) "rim joist" lagged to the exsiting 4x4's and anchored with heavy angles and an epoxied anchor.
Or forget the rim joist & just put a single angle on the end.
Your concept with multiple HL37's is way too complicated & too much work.
I'd install about 8 angles....two on each shed face and that's probably 2x as many as you actually need.
When I anchored the walls of our shed to the slab I used a .22 calibre gun-nailer. Then used it to toenail anything larger than a 2x4. Took about 2 hours, not counting moving all the crap out to make room to work and then putting it back in. Use the rght size nails and locatoins and it's a breeze. TEST beforehand in case the cement was a brittle mix done by some neophyte. And be accurate; it's really tough to pull a cement-nail out of cement once it's driven in. Wear ear protection; those 22 shells get really loud inside a small building!
The 4x4's are nailed to the 5/8" subfloor that itself is connected to the walls. The shearwall looks like 3/8" (or maybe 1/4") plywood with a decorative exterior. It bears a slight resemblance to the base Tuff-Shed with the addition of a side window, attic turbine vent, and drywall finished interior with electrical outlets and lights, but I have no way to confirm that. (The shed was installed by the house's prior owner.) I have boxes of stuff stored in the shed's attic, so the shearwall would be tested under lateral motion.
Anchoring the shed, even if only one anchor at each of the four corners, entails some expense and labor. IF/WHEN we get a strong enough earthquake to move the shed, the most likely damage is to shear off the electrical service that comes from underground at one of the outside walls and to move the shed such that I'd nead to empty it, and then move it back onto it's pad and re-attach electrical service.
If I anchor the shed the floor may survive, but the building might collapse or get tweaked so that it needs to be rebuilt or replaced. I assume that would be far more expensive than moving the shed a foot or two and re-attaching electrical service.
There is no nearby cliff. The pad extends at least a foot on each side, and the side and rear property lines are about 4 feet from the shed walls.
I'll consider your suggestions. But, in the end doing nothing may be the most economical.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.