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My main question: How can I push these boards back together so I can secure them to each other, ultimately repairing the couch?

I don't have a shop, and not many tools, and I'd prefer not to detach the upholstery if I can, as I'm not confident in my ability to re-attach it. I also can't figure out how to detach the springs, and I hope it's not necessary.

Where I'm At

The boards running along the front are cracked, and so the couch sags. I opened up the bottom and I can see the springs are pulling out one of the boards from the other where they were stapled together.

So far, I've tried to pull out the staples so I can push the boards back together and clamp them. I haven't been able to get some of the staples out, they just won't budge, or I can't get leverage on them.

I managed to get a clamp around the boards, but I could only get on it at the part where the boards are close together. As I tighten the clamp, the boards won't budge at all, no moving back together at all. Maybe the staples are in the way, or maybe I just don't have the strength to turn the knob.

Failed clamp

It's hard to tell from this pic, but the other end of the clamp is on the other side of the plywood, the flat side. I had to put the clamp much further down to even get it to reach the other side, see pic #3 further down. I thought I could push this section together to get the section in pic #5 together so I could get another clamp to bridge the larger gap, but it's not working.

Original Full Plan

Now let me share my original plan, so you can see the damage better, and have context about the clamps.

Couch Damage Photos

The boards separated

The cracks

Flat board is plywood, you can see that the plywood and the smaller board, the spring strut, have cracked, and the staples attaching the strut to the plywood have failed.

I plan to:

Cut and pull out all staples in the way (failed, got about half out)

Clamp the strut to the plywood (Failed, clamp too small? and won't tighten further)

Use wood screws to screw the strut to the plywood

Squeeze epoxy (or wood glue if that would work) into the split wood and plyboard. If not possible to get glue in the cracks then...?

Attach mending plates to bridge the splits

Like this: part 1 plan

part 2 plan

plates

I'll try to squeeze as much epoxy or wood glue as I can into the cracks before attaching the plates.

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    That mending plate looks like the kind used in making trusses. I've used one once. It was in pine. It's going to take a lot of pressure to insert that plate, I did it with a 4 pound sledge hammer backed up by a concrete floor. In this instance, you aren't going to have enough 'anvil' behind it even if you had something more than a 24 oz hammer. It is more typical of couch type furniture to use something harder than pine which will make it even more difficult. Consider sistering a board to the existing board or use steel mending plates - the type you apply several screws in.
    – quill
    Commented Jul 5 at 22:31
  • "...as much epoxy or wood glue..." There's only one real choice here if you don't want the mending plates to be pretty much doing all the work and that's epoxy. Wood glue makes v strong joints but only if they're thin. Since you have zero expectation of getting these surfaces into intimate contact epoxy is the glue of choice here. See numerous previous Answers here for tips on using epoxy effectively. But to echo @quill's Comment above, you'll either want to glue and screw a board across that joint (looks like there's plenty of room for that) or use a substantial screw-on mending plate.
    – Graphus
    Commented Jul 6 at 7:05
  • You can't fix this with the truss plates. You need to glue/screw new wood against the OSB to strengthen it.
    – gnicko
    Commented Jul 20 at 14:55

2 Answers 2

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The break is not just to the board which attaches to the springs. The chip board front has been fractured. It appears some of the staples which hold the fabric may or may not be holding as well as they originally did. For this repair it would be best to not mess with the spring attachment (unless something has come loose). As mentioned earlier, attach a mending plate with screws to the board which supports the springs along with epoxy. That mending plate will need multiple screws on each side of the break.

The fractured chip board is going to also require a mending plate but that may present other challenges. The chip board itself will never again handle the load on the couch. The larger plate shown in the original question may work if you could push those spikes into the chip board, which is not likely. You wouldn't be able to do this with a hammer. It may be possible to push the spikes in a few at a time using a deep throat C clamp. To see if that is possible, obtain another of those spiked plates, and some scrap wood to try it on.

There is a possibility a spiked mending plate may not support the twisting load on the chip board when several people sit on the couch. An alternative solution would be to attach a piece of 3/4 inch plywood to the chip board with screws and maybe some epoxy.

If that front chip board is thin, you may need to attach the screws from the front. Lifting some of the fabric would be necessary to do this. Looking at the original photos above, you probably have a staple or two that needs attention anyway. If you only take off some of the staples along the bottom, putting them back is trivial with an inexpensive staple gun.

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  • +1! One minor correction, this is OSB, oriented-strand board. Chipboard is the same as particleboard, make up of tiny chips, not big 'strands' or flakes (hence one other name sometimes used for this product, flakeboard).
    – Graphus
    Commented Jul 7 at 5:35
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To me, looking at the damage you have I would buy a brand new board a 1" by 4? or 6?" by the length that would find as long as possible along the chip board. I would then line everything up as well as possible with clamps and things then use a lot of screws to attach the new board to the OSB. You want the screws short enough they don't go all the way through the osb but deep enough to get a good grip, since the screws are short and it's OSB, I'd use at least 8-10 screws scattered around the board.

The big problem as mentioned about the plates you have is actually installing them. chances are you will actually do MORE damage to the couch and the OSB just trying to pound them in. The pine board you have a so-so chance of success but the OSB in my opinion will be near zero. You had the right idea of reinforcing it with a brace, but I would go with my suggestion from my first paragraph.

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