Is it ok to leave the wooden template on the wet concrete while it dry's?

[ched]

My apologies for displaying my shattering ignorance before you all.

I have dug out a square hole in my garden 50cm x 50cm x 50cm and constructed a simple wooden former of these dimensions to line the hole and fill with concrete.

I have an Altair Pier that I hope to eventually fasten to this concrete pad. I have a plywood template 50cm x 50cm with the 4 threaded rods going through it  and plan to pour the concrete tomorrow.

I am a little bit puzzled as the instructions seem to infer that this wooden template with the rods in actually pushes down onto the top of the wet concrete which I will then have to make sure is flat.

Presumably I have to leave this in place while the concrete with rods in harden off. The photo shows the box and the template ready for the concrete.
 

Please be gentle as I am completely ignorant about such matters however it seems counter intuitive to leave the wooden template lying on the concrete while it sets. Surely this will somehow need to be removed when the time comes to put the pier on the concrete to bolt it down onto the rods. As the concrete is not self leveling is the wooden template used to lay the spirit level on and ensure it is flat? 

Perhaps somebody who is experienced in this matter could point me in the right direction before I make a horrible mistake....

Many thanks for your time and any help would be very gratefully received.

Regards

[Pan Euro]

Put grease on the underside of the template that will help it release from the concrete mix. The point of it is to ensure the the rods are vertical in the mix and that it is also level in all directions. If not you will have problems with leveling your pier when you come to bolt it to the base. It what I did with mine.

[ched]

Thank you for your advice :-)

I am just mixing the concrete up now.

Many thanks

[Scorpius]

Yes - the template should remain in place for several days otherwise the bolts could move during initial curing creating issues when it’s time to bolt on the pier. You can use grease or motor oil to coat the underneath side and edges of the template but I recently discovered a generous coating of non-stick cooking spray works very well.  Although I opted to go with a concrete embedded pier, I’ve used the template trick on other projects so here’s what I would do.

First, use a thick (3/4”) piece of plywood that’s perfectly flat with no evidence of warping. Then cut it in a circular shape (assuming a circular pier flange) about a ½”-1” larger than the outside diameter of the pier flange. Then be as precise as possible when drilling holes in the template to ensure the bolts will line up and be centered in the holes of the pier flange. Use nuts & washers on the top and bottom of the template to keep the bolts exactly vertical and in alignment and then test fit the bolts into the pier flange holes to make absolutely sure they are lined up and centered. If one or more of the bolts are a little off, you can ream out the template hole(s) just make sure the nuts on the top and bottom are tight enough to prevent the bolts from slipping around inside the over-sized holes. Then immediately after the concrete is poured, push the bolts into the wet concrete so the bottom washers are flush or slightly below the surface of the concrete.

After pushing the bolts into the wet concrete with a slight twisting back & forth motion, – and this is very important – make sure the top of the template is level in two perpendicular directions. What this does is ensure the concrete surface you’ll be bolting to will also be level preventing the need to add shims under the pier flange to compensate for crooked bolts. You can also install two D shaped handles to grab on to when it’s time to remove the template after several days of initial curing. Just be sure to use short screws that don’t extend all the way through the plywood and then the screws can be removed and the handles re-used for some other purpose once the template is removed. Install the handles straight across from each other and in line with two of the bolts so there’s sufficient unobstructed space in two perpendicular directions to place an accurate torpedo level during the bolt embedding process.

What you’re trying to achieve is full contact between the concrete and bottom flange of the pier since the bolted connection is the weakest link in this type of installation. Otherwise you may need to install washers or shims in order to plumb the pier and that will raise the pier flange off the concrete creating a void between it and the bottom surface of the flange reducing your contact area.

After several days (3 or so) – and if you used enough cooking spray, grease or motor oil - a healthy, straight-up tug on the handles should pop the template off slick as a whistle with no adhesion of plywood to concrete. What you don’t want to do is insert something like a screw driver between the concrete and template attempting to pry it off since you’d be prying against green concrete which could gouge it out and mess up your nice flat surface.

If you follow these steps the template should come off with no problem and you’ll end up with full contact between the concrete and pier flange and a pier top plate that’s very close to level. While it’s true the mount can be adjusted to compensate for an out-of-plumb pier, the closer it is to level the better in my opinion if for no other reason than preventing a visually out of plumb pier.

Good luck and keep in mind that meticulous preparation and installation of the template will make all the difference when it’s time to bolt on the pier after at least several weeks’ time to ensure the concrete has fully cured prior to exerting any significant pressure on the embedded bolts.

[Scorpius]

Sounds like you're already pouring the concrete but unless I misunderstood, I'm confused as to why you would build a wooden box and insert it in the hole. Usually the concrete is just poured in direct contact with the earth forming the sides of the hole. My concern with a buried wooden box would be the wood will eventually rot away leaving a void between the earth and concrete. It also attracts termites but hopefully that's not a issue in your area.

[ched]

Thank you all for the advice.

I followed your suggestion Scorpius and it worked very well. I removed the wooden sides to the box using a string handle and once they were removed just back filled the gap.

Once again thank you.

[Scorpius]

Hi ched - Glad it worked out & be sure to post some progress pics of your build when you get a chance.

Maybe it's just because I'm in the middle of construction but this is one of my favorite sections of SGL. All the brainstorming and bouncing ideas back & forth has really helped me out and it seems as though we're all forming a sort of DIY construction network.

Hope the weather in your neck of the woods is better than mine. It's now been raining four straight days but looks like it may stop by the weekend so I can get back to the task at hand...