Concrete curb form

Reply

  #1  
Old 11-22-08, 09:09 AM
S
Member
Thread Starter
Join Date: Dec 2004
Location: South Florida
Posts: 1,178
Received 0 Votes on 0 Posts
Concrete curb form

I need to pour some concrete curbs on an existing concrete slab, the longest curb is 20 feet long by 5.5 inches wide by 9 inches high. This is a 20 foot span between two existing 6x6 posts. I'm enclosing my pole barn carport and the curb is the base for the wall framing per the architect's drawing, intended to raise the framing and sheathing above grade.

My problem is how to build the form. Questions:

(1) If plywood the material to use, what thickness and how to brace the form so it doesn't bulge in the middle?

(2) How to keep the sides from falling overin and other places, or falling apart?

(3) How to extend the lengths of plywood to 20 feet to get a smooth-sided curb?

I've poured concrete before on a smaller scale, just enough to know what a mess I will have if the form collapses or starts bulging or leaning!

Thanks!
 
Sponsored Links
  #2  
Old 11-22-08, 10:14 AM
Q
Member
Join Date: Apr 2007
Location: Canada
Posts: 436
Received 0 Votes on 0 Posts
There are different ways to do that, here's one: If the curb is at the outer edge of the slab, you can drive stakes into the ground to support the plywood forms. Nail the stakes to the plywood. The stakes should be driven until they are secure, the depth depends on the ground type and condition. If required to prevent bulging you can use braces angled into the ground for additional support. Commercially available 2"X2" stakes may or may not suffice, if not, you can make some out 2"X4"s. If the curb will not be along the edges of the slab, you will need to brace the plywood forms against a fairly solid surface until they are secure. All bracing should be done against a fairly solid surface to prevent bulging. If placing braces into the ground, loose soil should be dug until you get firm soil or the braces driven into some fairly solid soil before nailing to the forms. keep nails from protruding into the inner surface of the plywood. If you can push firmly outward on the forms and they don't give, you will be OK.

To get a smooth side after removing the plywood (i.e. no roughness at the plywood joints, you can cut some roofing paper or heavy vinyl to size and place that on the inside of the plywood, taped on if necessary.

QC
 
  #3  
Old 11-27-08, 03:14 AM
S
Member
Thread Starter
Join Date: Dec 2004
Location: South Florida
Posts: 1,178
Received 0 Votes on 0 Posts
That all sounds workable. Thanks for the advice!

I have few more questions about the curb that I'll post separately.

Thanks again.
 
  #4  
Old 11-27-08, 10:13 AM
nap's Avatar
nap
nap is offline
New Member
Join Date: May 2006
Location: north
Posts: 4,162
Received 1 Vote on 1 Post
Your curb is not very high so there will be very little (relatively speaking) side loading of a form.

You could use a 2X12 for the forms or if using plywood, simply stake it every couple of feet.

In commercial applications, they actually pour curbs that tall with only a forming machine that shapes the concrete as it is being laid down with no supporting form to keep it in place after it is poured. Of course, you would have to use a very low slump mixture (really stiff) but it is done all the time in road work and parking lots.



one thing that I don't understand:

I'm enclosing my pole barn carport and the curb is the base for the wall framing per the architect's drawing, intended to raise the framing and sheathing above grade.
this, along with your other post; it sounds like this is a footer. If so, I do not see it as being large enough or; am I misunderstanding and you aleady have a slab and this is merely a section of wall to keep the wood raised.

If the latter, concerning your other post;

I would not use this as the retention for the wall. I would set expanding anchors in the existing foundation before pouring this curb making sure to cover the threads with tape or whatever to prevent them from getting concrete on them where they will be above the curb.


and to where you are joining sections of plywood to lengthen it;

use a section of 2X to span the joint and screw the plywood to the 2X. It will hold it together and relatively flat. Place a stake directly outside of this joint for strength and support.
 
  #5  
Old 11-27-08, 10:49 AM
dhamblet's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Oct 2008
Location: PAcific Northwest
Posts: 264
Received 0 Votes on 0 Posts
Originally Posted by suobs View Post
I need to pour some concrete curbs on an existing concrete slab, the longest curb is 20 feet long by 5.5 inches wide by 9 inches high. Thanks!
Why not just use block and fill it in? Stuff some j bolts in for anchors
 
  #6  
Old 11-27-08, 03:22 PM
S
Member
Thread Starter
Join Date: Dec 2004
Location: South Florida
Posts: 1,178
Received 0 Votes on 0 Posts
Reply to nap: yes, sorry, not a footer - there's an existing slab, so it's just the bottom section of wall. The bottom of the sheathing needs to be 6" above grade and we added 3" because new turf was going in around it.

[QUOTE=nap;1471626]
I would not use this as the retention for the wall. I would set expanding anchors in the existing foundation before pouring this curb making sure to cover the threads with tape or whatever to prevent them from getting concrete on them where they will be above the curb.
QUOTE]

The vertical 12" rebar mentioned in the other post will be set min. 6" into the slab with epoxy and connected with a horizontal rebar in the curb. So I think that takes care of retention of the wall, but I'm still confused about the expansion bolts. I can see the advantage of setting them in the pour (not having to drill a 9" hole!). Haven't done this before - do I set them, then place the sill plate after the concrete is dry, then tighten the nuts? If so, I'm still wondering how long the concrete has to cure before I can tighten. Also wondering about whether the horizontal rebar or the bolts should be off center.
 
  #7  
Old 11-27-08, 03:26 PM
S
Member
Thread Starter
Join Date: Dec 2004
Location: South Florida
Posts: 1,178
Received 0 Votes on 0 Posts
Originally Posted by dhamblet View Post
Why not just use block and fill it in? Stuff some j bolts in for anchors
Reply to dhamblet: poured curb is the way the architect & engineer spec'd it and it was permitted as planned. I'm in S. Florida BTW and there are wind load regs specific to enclosing a carport, and I'm told it's not a good dea to vary from the plan if I want it to pass inspection. S. Florida codes are also why the 6x6 framing, even tho the original was 2x4 (one existing wall and one of the four 10x20 ft bays which is enclosed into a shed) .
 
  #8  
Old 11-27-08, 03:30 PM
S
Member
Thread Starter
Join Date: Dec 2004
Location: South Florida
Posts: 1,178
Received 0 Votes on 0 Posts
Here's my other post for reference:

Originally Posted by suobs View Post
The architect for my carport enclosure project (see "Concrete curb form" thread) specified 1/2" x 9" expansion bolts to tie down the 2x6 sill plates to the 5 1/2" by 9" concrete curb. If I am understanding this right, the bolts should be installed after the concrete is poured (not inserted into the wet concrete).

1. If I am right about drilling, how long does the concrete need to cure before I can drill the holes and install the expansion bolts?

2. Either the horizontal rebar or the bolts need to be installed off-center so the bolts don't hit the rebar. Fromn the drawing it looks like the bolts might be intended to be off center towards the outside of the curb. Does it matter?

3. Finally, I'm not finding 20 foot lengths of rebar. How much should the separate sections overlap?
 
Reply
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description: