[keenxxx]

I have a 30x30 concrete slab @ the rear of our home that uses 2x4's to divide it up. The 2x4's have almost completely rotted. A search online has remedies for standard 3/4" expansion joints. Are there any alternatives to using 2x4's again? I came across a few urethane products but didn't know the exact application. Heres one :https://www.bestmaterials.com/detail.aspx?ID=18466

Any suggestions would be great. Thanks.

 

[Nealtw]

I would just fill them with concrete, maybe add colour to make it look like wood.

 

[huesmann]

You could use 2x4s again, assuming you can dig out all the old rotted ones, but you'd probably have to shave them down a few 16ths to get them back in the slots. I'd be tempted to just concrete per Neal's suggestion, or use some massive backer rod and elastomeric filler.

 

[SeniorSitizen]

Redwood has long been the tradition for wood in that application. Home Depot advertises a 4 pack of 2x4's 8' long for $100.74.

 

[keenxxx]

Redwood has long been the tradition for wood in that application. Home Depot advertises a 4 pack of 2x4's 8' long for $100.74.

Home Depot doesn't sell straight lumber:biggrin2:

I watched a video where someone used PT 2x4 lumber for dividers. I thought how long before the PT twists and warps? I have built 2 decks as of late using 99% of my lumber from HD. The PT is soaking wet & the Con Heart Redwood can have mid moisture content.

When dividers are originally installed are they placed after the concrete is done? Any way to secure the wood in case it want to move?

 

[Nealtw]

Home Depot doesn't sell straight lumber:biggrin2:

I watched a video where someone used PT 2x4 lumber for dividers. I thought how long before the PT twists and warps? I have built 2 decks as of late using 99% of my lumber from HD. The PT is soaking wet & the Con Heart Redwood can have mid moisture content.

When dividers are originally installed are they placed after the concrete is done? Any way to secure the wood in case it want to move?

Lumber is not straight unless it was dry before it was cut to shape.
The wood was there before the concrete was poured.

 

[keenxxx]

I would just fill them with concrete, maybe add colour to make it look like wood.

Thought about fortified Type S mortar w/ a gravel base but it would probably crack quite a bit in time.

 

[stadry]

IF you fill joints w/concrete, you'll wind up with thin lengths of concrete w/lots of cracks,,, definitely NOT any conc pro's recommended repair method,,, be a sport - pop for the 2x4 cedar/redwood & enjoy a good driveway,,, if, in the future, you want to replicate this method in new constr, just use plenty of stakes & place conc same day you set the joints
prior to the acceptance of diamond saws, many conc roads were constructed using 1x8's for joints
btw, we still install driveways this way if arch shows it on plans & won't consider submitted alternates

 

[keenxxx]

Lumber is not straight unless it was dry before it was cut to shape.
The wood was there before the concrete was poured.

Just pulled the dividers. They used 2x2 redwood. They had nails driven in the sides to anchor into the concrete when poured. Thanks.

 

[stadry]

what's under the 2x2 ? no sawcut ? is there a crack under them ? 30x30 has to have joints or lots of random cracks by now,,, nails are so it wouldn't 'float' out of the wet mud

 

[keenxxx]

what's under the 2x2 ? no sawcut ? is there a crack under them ? 30x30 has to have joints or lots of random cracks by now,,, nails are so it wouldn't 'float' out of the wet mud

No saw cut. Had to been installed w/ wet concrete so the nails would hold wood in place. How would new wood stay affixed w/o popping loose?

Pic's attached.

 

[stadry]

there ARE cracks,,, i see 1 under removed 2x2 + other random cracks
if it were our job, we'd clean the recess, add a bead of const sealant, then use tapcons
what an odd joint pattern for such an easy job,,, that's probably the cause of the random crking

 

[keenxxx]

there ARE cracks,,, i see 1 under removed 2x2 + other random cracks
if it were our job, we'd clean the recess, add a bead of const sealant, then use tapcons
what an odd joint pattern for such an easy job,,, that's probably the cause of the random crking

In regards to mounting the 2x2's. Tapcons would be great except the channel base is not solid. There is a crevice on the base. Matter of fact water, draining in in a few spots causing soil erosion - what a mess.

 

[3onthetree]

That pattern looks kinda cool at least visually. I don't think there are pavers 1 1/2" thick, but if you can find something height-wise and a wet saw for width, how bout that instead if you have hesitation on the wood? Was also thinking zoysia grass, but that wouldn't work unless it was open to below.

 

[keenxxx]

That pattern looks kinda cool at least visually. I don't think there are pavers 1 1/2" thick, but if you can find something height-wise and a wet saw for width, how bout that instead if you have hesitation on the wood? Was also thinking zoysia grass, but that wouldn't work unless it was open to below.

Thought about some polymer sand stuff that is usually used between pavers. Problem is I need to now seal the dividers as I have erosion under the slabs in a few places. Probably pour sand or mortar in the eroded spots and hope it flows where it’s needed.

 

[stadry]

prime reason those cracks are there is because the concrete was 'directed' to crack there by whoever placed the 'dividers'/joint pattern,,, some dummy didn't realize concrete follows its own rules & likes to be square,,, the reason there's random cracking ( those other cracks ) is the same dummy,,, there's a formula for slab section size but not worth it for this thread.
define 'erosion' ?
clean out the cracks & run a bead of 'sealant' to close them up,,, IF you fill the cracks 1st w/anything, use 1/2 & 1/2 mix of play sand & vermiculite OR foam-in-a-can,,, then install redwood/cedar/whatever wood you choose,,, polymeric sand won't work at 2"x2" impo

 

[gbengoose]

Never heard of wood used as an expansion joint so I googled images and stumbled upon this repair article.

https://www.motherdaughterprojects.com/blog/how-to-replace-wood-expansion-joints-in-sidewalk

Search for "slab gasket"

 

[keenxxx]

Never heard of wood used as an expansion joint so I googled images and stumbled upon this repair article.

https://www.motherdaughterprojects.com/blog/how-to-replace-wood-expansion-joints-in-sidewalk

Search for "slab gasket"

Interesting, had no idea they went that large on the gaskets.

I did find a self leveling Polyurethane than will do 2" gaps by Masterseal. My only concern w/ the gasket would be even placement and how well it stays put. Self leveling would positively seal the joints but would require more labor to install. Thanks.