Another concrete question...

[KansasArt]

But at least it's not another "My contractor screwed up my slab" question!

Pouring a small sidewalk, maybe 16' total length. From the deck to garage door. Will be done with bags.

My question can I use 4X's for the forms and leave them in? I would then stain them the color of the deck. Sorta like picture framing each section.

My concern is the concrete expanding/contracting. Would it expand enough to crack the slabs since there will be no room for it to expand to with the 4X's being non moveable? Only doing this for aesthetic reasons. Thought it would look nice.

If that shouldn't be done I'll just use the normal 2X4's for the forms and then remove them. Which leaves another question...I'll be doing this in sections as I can't mix the bags fast enough to do all at once. Can each section just **** up to one another, or should there be something in between them?

Thanks!

 

[dcg9381]

My question can I use 4X's for the forms and leave them in? I would then stain them the color of the deck. Sorta like picture framing each section.

Sure... Know how many not-so-removed concrete forms I've seen in my state?
Thing is, you might as well build a wood deck, place it on the ground, build poor drainage around it and wait. It's gonna go to **** in a few years depending on your climate.

My concern is the concrete expanding/contracting. Would it expand enough to crack the slabs since there will be no room for it to expand to with the 4X's being non moveable? Only doing this for aesthetic reasons. Thought it would look nice.

Anecdotally, I don't see much movement in expansion joints. But wood on the "outside" of concrete is likely to deform over time.

Can each section just **** up to one another, or should there be something in between them?

Here, just off the bottom of the concrete we always have steel.. Sometimes wire mesh for sidewalks. You may need expansion joints.. and I wouldn't use wood, I'd use composite. I'd pour one "expansion joint" section at a time, but others may have better ideas.

 

[Leaflessshadetree]

I'd stain the wood first, then cover it (I'd use thin plastic and tape) before pouring the concrete.

 

[PopcornSutton]

Wood or no wood, you need a control joint typically every (5 feet correction) and an expansion joint every 30 feet. But you can design the control joint pattern any way you wish. And a control joint can serve as the end of one pour and pour against it for the next pour, just edge both sides.

A functional control joint should be at least 1/4 depth of the slab.

 

[KansasArt]

Well, there won’t be any control joints. Just about every 4’ a new section.

 

[Rusted Nut]

It use to be common in the PNW back in the ‘70’s to use permanent cedar 2x4 forms for sidewalk and driveways. Stain first, then pour. They work fine as expansion joints. Most rot out in 20 years or so though.

 

[PopcornSutton]

Well, there won’t be any control joints. Just about every 4’ a new section.

Then you have control joints every 4 feet.

 

[ConCretin]

Concrete doesn't get any bigger than the day it was poured. It shrinks as it sets and rarely expands any more than it shrunk. No worries from that standpoint. Protecting the lumber from rot might be.

If you remove the forms and place concrete against concrete, I'd probably pin them together to keep the surface aligned.

If you get freeze thaw conditions, you want air entrained concrete. Edit; Some bagged concrete claims to be air entrained but I didn't see any specs on the level they of air they achieve. Ready mix would generally be spec'd around 6%. Pay close attention to the quantity of mix water. Concrete strength goes downhill fast if you use too much.

 

[firebirdparts]

If you are going to pour it in sections and leave wood between the sections, use a 5 quarter deck board for that part of the form. It looks better.

 

[NUTTSGT]

Keep in mind, that wood will rot eventually. It'll probably also heave the first winter or two and be above the edge of the concrete.

 

[PopcornSutton]

I personally would not leave wood in a sidewalk. The proper ground contact treated lumber (4x4) on the sides as forms left in place, maybe.

 

[KansasArt]

Thanks for the advice. My plan is to coat the 4X’s on 3 sides with some type of tar/asphalt sealer. And have them sitting on the gravel base. Ik that’s only gonna buy me a few more years before rotting.

 

[bluedog225]

It sounds like you’re building sections of sidewalk with spaces between them. Sounds like a good plan.

You might just build them as independent little slabs with appropriate steel or mesh in them. Then move onto the next one.

You can leave whatever gap you want in between. if you fill the gap with the wood framing, that’s fine. But it won’t last all that long. Or you can pull the wood and fill it up with gravel. It’s a nice look as well.

Another option is a run of bricks or some small patio pavers or stones and a gravel base between the slabs. Breaks it up and looks nice.

 

[Max]

Thanks for the advice. My plan is to coat the 4X’s on 3 sides with some type of tar/asphalt sealer. And have them sitting on the gravel base. Ik that’s only gonna buy me a few more years before rotting.

I had a pool deck that was done similarly to what you are proposing. Instead of tar sealer they used redwood. I wasn't a fan, as the wood would rot and I would have to replace it periodically.

If you really want the look of a wood border and joints, I would go with something like trex instead of wood. It will last probably 10x longer than wood will and it won't rot. Trex isn't as strong as wood, so you'll have to use more stakes to keep it firm during your pour, but otherwise I don't see any downside other than a bit more cost.

BTW, don't use tar. It'll look ugly, make a mess, and it won't last any longer than pressure treated wood.

 

[KansasArt]

Trex is only about 1” thick. I’m looking for a 4” wide border. Do they make composite 4X4’s?

 

[manwithtools]

Do they make composite 4X4’s?

Yes.

 

[Toolfool]

Use a 2x whatever your concrete depth is to frame the end of your pour. Drill a few holes through it to pass 3/8" rebar through to tie each section together (for when you pour the next section). I personally use rebar and pour sidewalks 3" thick. When I did my front walk here in Florida, everyone told me I only needed 2" thickness and NO steel. I built custom homes in the PNW for 30 years. I took a look at the deteriorating 2-1/2" 5 year old driveway the original builder poured, I ignored them.

 

[PCustoms]

If I wanted a border I'd either pour a colored concrete or stain/stamp the sidewalk.

Putting wood around concrete seems counterproductive

 

[KansasArt]

Well, I’ve abandoned the idea of using wood boarder. Lots of good ideas for me to think about. I especially like the tip from @Toolfool of running the rebar between 2 sections.

Thanks guys!