Questions and Answers for SAKRETE 8 in. x 48 in. Concrete Form Tube

A:  Here's the theoretical answer: One 60-lb bag of concrete mix will fill a volume of 0.45 cubic feet One 80-lb bag of concrete mix will fill a volume of 0.60 cubic feet The volume of an 8" diam x 4 ft long tube is 1.39 cubic feet A 4x4" is actually 3.5"x3.5". If the 4x4 extends the full length of the tube, its volume will occupy 0.34 cubic feet of the tube's 1.39 cubic feet; thus, you only need enough concrete mix to fill the remaining 1.05 cubic feet. And that can be done 140 lbs of concrete mix [in this case one 60-lb bag plus one 80-lb bag]. And that can be done with

A:  To pour an 8" x 48" form tube including the 4 x 4 post will take approximately 3/80lbs. bags of concrete mix.

A:  We are not aware of depth required for your project. With that said. The Form Tubes can be cut to a specific length.

A:  Yes, you can cut/trim these tubes to the desired length.  For cutting I use a reciprocating saw.  

A:  Yes you can! It is heavy thick paper/cardboard tube. A fine tooth saw (hand or power)works well to trim. A razor knife can also work but time consuming. 

A:  You can, but the cardboard is thicker than most cardboard. I often cut these using my table saw into 1-3/4 inch tall rings for use as concrete forms for round stepping stones. You could cut these using a tool that is less aggressive, like a hand saw or jig saw. These would be difficult to cut with razor knife. 

A:  Melpreston, Yes. Form Tubes can be cut down to specific length. The are multiple ways to cut a form tube. A standard hack saw, a skill saw or even a box knife are a couple of ways to cut them. The material is condensed paper.

A:  Yes, with a sharp knife or box cutter you can easily cut these to length 

A:  Doing the math, a 60# bag (.45 cu.ft.= 777.6 cu.inches) of readicrete will fill a little more than 15 inches of an 8" diameter tube (pi x 4 squared = 50.27 cu inches)... 777.6 ÷ 50.27 = little more than 15 inches)

A:  To pour an 8" Diameter x 48" Depth Form Tube will take approximately 3/80lbs. bags of concrete mix.

A:  Gary, Sakrete does offer 10" inch form tubes. If further assistance is required. You can contact us directly at 1-866-SAKRETE (866-725-7383).

A:  they do come in ten inch but call ahead to make sure in stock

A:  Joseph, No. Unfortunately we don't have 6" diameter tubes.

A:  Pergola Builder, Typically the circumference of the hole is 3 times the width of the post. However, in some cases a structural engineer may require certain specifications be followed, Should you have any further questions you can contact our support team directly at 1-866-SAKRETE (866-725-7383).

A:  It will be a slightly tight fit, but I don't see why not.

A:  It depends what it’s for. If it’s a deck, check your local code. It might require a 14” concrete pier. You could get away with a 12” if code doesn’t require 14”. I wouldn’t do 8” for a 6x6. 

A:  Erika, Yes. Concrete Form Tubes may be recycled with other paper products if possible.

A:  I cut mine in half and used it on a light post /flagpole and worked out perfect

A:  Yes

A:  Thank you for your question. Yes. Fast Setting Concrete Mix can be used. However, a Form Tube with a diameter of 12” inches will be needed. Hope that helps. Please contact us at 1-866-256-7404 if you have any other questions that we can resolve to your satisfaction.

A:  Yes. These are great to use with fast setting concrete.

A:  It should be fine. I would seal the area with a prime to help preserve the 4x4. Also pitch the cement down away from the 4x4 so water will run off. And put a nice bead of caulk around the 4x4 to the cement to keep water from getting in any gaps.

A:  Thank you for your question.  Oldcastle strives to provide the best possible products and customer experience.  Please contact us at 1-866-256-7404 so we may gather more information and resolve to your satisfaction.

A:  If the wood is pressure treated you will be fine!!!

A:  Good question. Chances are the posts are ‘in’ concrete underground already. I like your idea and I think there is a sound way to do it. There is a ‘flashing roll’ (tape) It is a thick waterproof self adhesive flashing used around windows & doors to repel water. It comes in a 6” width. Make sure the bottom of the posts are dry & clean and adhere the tape around the bottom where the concrete will go. Works best and is most pliable and ‘ sticky’ when warm. So , if you add this step to your process , it should add longevity to your posts. Good luck

A:  It will work if the wood is treated with some kind of sealer.