Framing a wall on top of uneven concrete

[Todd Solomon]

Hi fellas,

I'm deep into my shop expansion in my basement, and need to frame a 40' long wall on top of very uneven, but nice and thick, low concrete wall. I got a quote of $700 to pour a concrete footing with stud anchors, but yikes, I don't want to spend that kind of cash.

This wall-frame will go from this low concrete wall to the existing ceiling. It will need to support a lot of weight and moment (lumber rack, and cantilevered storage shelves for the shop), so I'm building it out of 2 x 6s. It doesn't need to be load-bearing for the ceiling above.

I've been thinking about installing a 4 x 6 horizontally, leveled and resting on short 4 x 6 pillars, with threaded anchors going through each pillar's center and expoxied to the concrete. I've also thought about pouring a concrete footing, but building the forms would be challenging, as this concrete is extremely uneven.

Any suggestions would be greatly appreciated.

Thanks!

Todd

[Bob Michaels]

Todd, you really don't need 2x6, 2x4 is more than sufficient for this job. I would scribe a 2x6 base plate to level up the low irregular wall and anchor that plate into the wall. The anchoring method would depend upon how the existing low wall is constructed, i.e. hollow concrete block, poured solid concrete, etc. If the wall is solid concrete I would drill it and epoxy in threaded anchor bolts which would bolt the bottom 2x6 plate to the low wall. If it is hollow concrete block, use 8" L shaped standard anchor bolts and fill the core of the block with mortar mix. Frame the wall in 10' sections using single top and bottom plates and then run a second top plate overlapping the 10' joints by at least 32". Studs should be 16" on center and well nailed thru the top and bottom plates into the ends of the studs. You could opt, as you mentioned, to simply form and pour a concrete cap with anchor bolts on top of the existing low wall. Make sure to tie the new concrete to the low wall with 1/2" rebar every 48". Forming and pouring (I'd just use a pre-mix concrete like Sakrete) is really no big deal to do. You don't need to do this pour all at once, just stick 1/2" rebars into the end of the concrete between pours and that will make the new footing act as if it were a continuous pour. Hope this helps.

[Joe Chritz]

Using blocks would be a simple fix. You can level it as you set the blocks and end up with a flat top for building you wall. Use any of the methods above to secure the wall.

If the floor is bad enough that won't fix it you may want to think about doing some replacement.

Joe

[Mark Hubler]

How about building a sill plate out of three layers of 1/2" plywood, so that it will follow the rough surface. Cut the plywood in the 4' direction, so it will be the most flexible. Use drill anchors and overlap the splices. Fender washers under the drill anchor nuts will spread the load. Toe-nail the studs into the plywood sill, use A35 simpson clip if you are really concerned about the attachment.

[Ben Grunow]

A true wood worker would scribe a timber to the wall so the top was level and the bottom sloped to fit... unless this requires a 12" thick timber. How crooked is it?

If the wall is covered (ply or drywall etc) I would go the plywood plate route. Plenty strong and easy to do.

Ben

[Bruce Wrenn]

How about getting a mason to lay a couple of courses of bricks, or a course of 6" blocks? He could "hog out" any low spots. Six inch blocks will be 5 5/8" wide, almost the same as 5 1/2" width of a 2X6 piece of wood. Drill anchor bolts into concrete prior to laying masonry units. Use coupling nuts for threaded rod and threaded rod to extend them up though blocks for anchor bolts. As long as blocks are laid in a straight line across the top, you could measure and cut each stud to desired length. We do this all the time in renovation projects. Seldom do we find a "flat and level " floor.

[dan moran]

could you drill some red heads or wejits into the top of your low wall?

that way you could bolt your treated bottom plate wherever you want (i.e. inbetween the studs). lay out the wall on the bottom plate, plum up to your top plate and lay that one out, measure all your studs and write your numbers on the plate with a sharpie, cut and assemble, use 6 framing nails (and some adheisive if you want) to secure the studs to the plates.. (3 top 3 bottom, toenailed from different sides). if theres a gap in the bottom plate anywhere you can fill it with some liquid nails or caulk or whatever you want..

if you want to secure the studs in the middle of the wall just make some short california corners with a piece of green plate and a piece of whitewood. Secure those guys to the wall so they sister your studs(every 3rd or 4th stud should be fine) with some liquid nails and tapcons or whatever mechanical fasteners you have.

adjust your studs and pop em into the corners and then sheet the wall however you want to..

its easier to work from something that you know is (reasonably) straight like the joists toward an uneven surface like concrete..