Casting new panels for a prefab garage?

[fex10]

Has anyone done this? I've seen people have casts to make prefab garages (aka Compton garages) from home so maybe it's doable. I was thinking of making a cast from wood, putting in my metal rebar, and filling with concrete. My only concern is how to make the concrete strong enough considering that these panels are quite thin. I know that these "home businesses" vibrate the concrete to strengthen it.

My concern is that maybe the commercially produced garages use pressed concrete panels, and in my experience it's difficult to make good strong concrete.

The panels have a brick pattern on them but I'm not concerned about that.

I've got about a dozen panels that were damaged in transit and I cannot locate the manufacturer to buy new ones.

 

[ntb]

Perfectly doable if you're handy. Ideally, you'll need some mould release agent to get it out of the mould and some spacers for your rebar to keep it away from the surface (or it will rust and blow out).

Concrete continues to stremgthen over a very long period of time. After a day maybe 10% strength, after a week it will have reached about 50% strength, 75% after a month. If you leave it in the mould to harden for a couple of days you should be fine to handle it.

Make all the sides of your mould removable to enable the cast to be freed more easily. Gentle taps with a rubber mallet may be needed.

 

[fex10]

Thats great that someone has some experience and says it could be done.

Mould release agent, any suggests on a brand?

I've worked with rebar before but not on such a small scale. For spacers I'll look for something plastic so it doesn't blow the concrete and something thin and minimal so it doesn't create weak spots.

My other consideration is that I need to cast the holes.

The original panels use concrete mixed with stones that look around 8mm diameter. Do the stones add strength or is that done to save money? The stones certainly make drilling difficult afterwards!

 

[Burnerman]

A firm called Cementone do a mould release agent, if you can find a supplier.
Prefab panels are vibrated well to allow the settling of the concrete- you can help things along by gently tapping the sides of the mould, and the concrete will settle.
Use a small pea gravel aggregate, make any bolt holes with dowel before the concrete is 'green' and consider wire mesh for the thinner parts of the panel for reinforcement....expanded metal is ideal.
Good luck with the project.......I found some fairly near matches for my workshop extension from a Compton brochure.
John

 

[fex10]

Thanks. This prefab is an unusual design, I know that most other prefabs use a more standard panel design that could be matched up with other manufacturers panels.

The biggest drawback might however be the fact that one mould can only make one panel at a time. I have a dozen panels so I need to do one an evening, and wait two days before doing the next. Maybe I should make three moulds and that would really speed things up. Doing one at a time is just bad economy, having to clean the tools up afterwards etc.

make any bolt holes with dowel before the concrete is 'green'

Before the concrete is green? Would the dowel not be put in place before the concrete is poured in?

 

[Burnerman]

Make the holes anyway you can, really......sometimes it's best to suspend the dowels in place, others it's best to bore the hole when the compo is green or just going off and then leave the dowel I'm place for a while longer- turning it occasionally to allow you to withdraw it when the concrete is firm enough.
John

 

[ntb]

You can get purpose made plastic spacers (in different sizes and depths) that clip onto the rebar but it's a quarter century since I've had my hands on them so I can't suggest where to get them.

In the past, I've formed cavities with polystyrene wired into place - you just bust it out later but if it's bolt holes then dowel is best like Burnerman says. If it gets stuck, drill it out with a cheap spade bit.

Without a vibration table you are almost certain to get some air bubbles marring the finish but I wouldn't worry about them.

Multiple moulds will obviously speed things up but I would double check the output from each one on the first cast even if I was convinced I'd made the moulds identical.

Oh, and the stones (aggregate) pretty much determine the strength of the concrete once you've reached the optimum water/cement ratio for strength. For really strong concrete I used to use granite chippings.

 

[leeco]

What you could do if you have un damaged panels is buy 50 Lts of latex and make a mould of one of the sections buy painting it on with a brush giving it about 30 - 40 coats the building some wooden frame round the thick latex mould you have made then you can make as many sections as you want.

 

[leeco]

A firm called Cementone do a mould release agent, if you can find a supplier.
Prefab panels are vibrated well to allow the settling of the concrete- you can help things along by gently tapping the sides of the mould, and the concrete will settle.
Use a small pea gravel aggregate, make any bolt holes with dowel before the concrete is 'green' and consider wire mesh for the thinner parts of the panel for reinforcement....expanded metal is ideal.
Good luck with the project.......I found some fairly near matches for my workshop extension from a Compton brochure.
John

Vibrating the concrete is to get the trapped air out of the mix.