Board concrete form moulds

[Declan52]

It might look and sound an easy enough task but shuttering is far from it. As above you need to think about how you prop and hold it all in place if you go the wet concrete route.  Even a small wall  maybe 500mm high will want to move.  That's a lot of weight pushing out. Then it's all in the quality and consistency of the mix.  Using a fine enough aggregate so it's smooth and how much you poke it to get rid of air so it's not full of gaps. 

 

If you go down plastering then it's very time sensitive.  You need to get it on the wall smoothed of then your  mould up and in place in a few short minutes.  Then it's how much pressure is enough to give you enough of an impression but not squeeze it out of shape. 

Do not under estimate how much work this will be.  That's why I mentioned the trial wall.  

[Alexphd1]

Does any of your joiners have experience in shuttering? We have a guy who is helping us one day a week just now who specialise in shuttering, could be handy for next project with a curved concrete staircase.

 

I don't think the one sided ICF will give you the effect you are looking for, it's more plyboard than planks so a relatively smooth finish. 

 

I think diy EPS EWI is a pretty cost effective form of insulation, you get the insulation exactly where you want (on the outside of the building) and pretty good for no thermal breaks. 

 

 

Edited March 29, 2019 by Alexphd1

[Alexphd1]

Would concrete block layed on the side be easier to use for one side of the shuttering than durisol?

[Sue B]

Removing the mould from a “plastered” concrete wall will surely pull the concrete off too?  And / or it will leave residue in the mould for the next application?

[Declan52]

5 minutes ago, Sue B said:

Removing the mould from a “plastered” concrete wall will surely pull the concrete off too?  And / or it will leave residue in the mould for the next application?

You oil the timber up so it doesn't stick to it. 

[Sue B]

Will that not stain the concrete?  I was thinking along the same lines (like getting a cake out of a tin) but thought the concrete would show

[K78]

41 minutes ago, Alexphd1 said:

Would concrete block layed on the side be easier to use for one side of the shuttering than durisol?

 

That’s a good idea. 

 

I did want to build with block and ewi. The cost of EWI and the associated renders put me off.

 

My reasons for using durisol(or similar) is that it is easy to dry stack and cut, the insulation is built in, It’s weather proof and is really easy to chase cables for electrics. Perfect for the diy approach. 

 

My groundworkers have done shuttered retaining walls before. They suggested one for my site but it was too expensive and I didn’t want to risk a blow out on a 4m x 14m wall. 

 

The joiners are both experienced and I know them well. Half the battle is having people you trust on site. As soon as many tradesmen hear “self build” they think £££

[Declan52]

49 minutes ago, Sue B said:

Will that not stain the concrete?  I was thinking along the same lines (like getting a cake out of a tin) but thought the concrete would show

Think of it more like butter for a souffle.  It allows the concrete to move but won't stick.  It's a special mould release oil you use or if you cant get that then vegetable oil will work the same. 

[Temp]

One possibility, but a lot of work,  might be to make your own concrete "paving' slabs and then "tile" the wall with them. Each slab would have to be made in a wooden mould. I made coloured paving slabs that way with my dad about 1970.

[mvincentd]

i'm actually going to experiment next week with rendering a wall with Thistle Onecoat then stamping it with board.  I know from prior experiments that the board can create suction and drag the wet muck off with it, and also that if too dried it won't take the stamp, so the working time window of receptive surface is quite short.  I wouldn't want too much wall rendered and drying at once.  It shouldn't be any great problem to do it in small sections anyway.

I did one boardform wall with poured concrete.  You need a product called Adowax to smear on the wood as a release agent.  I just used rough sawn 4 x 1 and 6 x1 from Travis.

Typically for a poured wall the concrete will be a pump mix, so not stiff, and it will get pokered a lot to remove air.  I fear without these in your mould system you will get voids in the surface that will really spoil the aesthetic.

 

[K78]

23 minutes ago, mvincentd said:

i'm actually going to experiment next week with rendering a wall with Thistle Onecoat then stamping it with board.  I know from prior experiments that the board can create suction and drag the wet muck off with it, and also that if too dried it won't take the stamp, so the working time window of receptive surface is quite short.  I wouldn't want too much wall rendered and drying at once.  It shouldn't be any great problem to do it in small sections anyway.

I did one boardform wall with poured concrete.  You need a product called Adowax to smear on the wood as a release agent.  I just used rough sawn 4 x 1 and 6 x1 from Travis.

Typically for a poured wall the concrete will be a pump mix, so not stiff, and it will get pokered a lot to remove air.  I fear without these in your mould system you will get voids in the surface that will really spoil the aesthetic.

 

 

Im going to have a chat with the joiner and groundworker tomorrow. 

 

I’m thinking of shuttering the walls starting from the bottom up, and doing each wall with 4 separate, vibrated pours on top of each other.

[K78]

4 hours ago, Temp said:

One possibility, but a lot of work,  might be to make your own concrete "paving' slabs and then "tile" the wall with them. Each slab would have to be made in a wooden mould. I made coloured paving slabs that way with my dad about 1970.

 

It’s a option worth considering. 

 

I did wonder about using reclaimed concrete sleepers, but the weight would be crazy. 

 

 

[Declan52]

25 minutes ago, K78 said:

 

Im going to have a chat with the joiner and groundworker tomorrow. 

 

I’m thinking of shuttering the walls starting from the bottom up, and doing each wall with 4 separate, vibrated pours on top of each other.

You could build in some threaded bar into your icf. Do your pour so they are solid.  Then use these to hold your mould or shuttering to the wall.  

It will take a fair bit of work making them all the same distance apart in height so your mould slips over the bars easily each time.  

Most shuttered walls have holes in them anyway like can be seen in your pics so once the wall is finished you could grind them of as close as you can get without hitting the concrete  and then drill them out so they sit below  the surface.  Will look like a normal shuttered wall.

Not sure you could patch the hole in and make it look good unless you are going to paint the concrete.

[K78]

5 minutes ago, Declan52 said:

You could build in some threaded bar into your icf. Do your pour so they are solid.  Then use these to hold your mould or shuttering to the wall.  

It will take a fair bit of work making them all the same distance apart in height so your mould slips over the bars easily each time.  

Most shuttered walls have holes in them anyway like can be seen in your pics so once the wall is finished you could grind them of as close as you can get without hitting the concrete  and then drill them out so they sit below  the surface.  Will look like a normal shuttered wall.

Not sure you could patch the hole in and make it look good unless you are going to paint the concrete.

 

That’s a great idea. My biggest concern was tying the concrete to the blocks, as it’s heavy. 

 

I love the rough look of concrete. Would be a sin to paint it. 

[Declan52]

2 minutes ago, K78 said:

 

That’s a great idea. My biggest concern was tying the concrete to the blocks, as it’s heavy. 

 

I love the rough look of concrete. Would be a sin to paint it. 

You could have expanding metal mesh strips acting like ties. 

https://www.screwfix.com/p/sabrefix-reinforcing-coil-galvanised-dx275-65mm-x-20m/94846

Build strips of these into your wall as you go up.  

[Temp]

1 hour ago, K78 said:

 

I’m thinking of shuttering the walls starting from the bottom up, and doing each wall with 4 separate, vibrated pours on top of each other.

 

If we assume each pour is 0.7m high (about 2ft) the average pressure is..

 

H*Rho*g/2

Where H is the depth and Rho the density of concrete

 

= 0.7*2400*9.81/2= 8,240 N/sqm. 

 

That's a force equivalent to 840kg per square metre pushing out sideways. If it moves or bends then the concrete pours out of the bottom. Make sure the shuttering is well designed. Your carpenter might not be the best person to do this.

 

 

Edited March 30, 2019 by Temp

[K78]

5 minutes ago, Temp said:

 

If we assume each pour is 0.7m high (about 2ft) the average pressure is..

 

H*Rho*g/2

Where H is the depth and Rho the density of concrete

 

= 0.7*2400*9.81/2= 8,240 N/sqm. 

 

That's a force equivalent to 840kg per square metre pushing out sideways. If it moves or bends then the concrete pours out of the bottom. Make sure the shuttering is well designed. Your carpenter might not be the best person to do this.

 

 

 

That’s crazy. I had no idea 0.7m high 60mm thick concrete would create that amount of force. Might be time for a rethink. 

 

Now I see why there are no YouTube videos on this.

 

The risk of a blowout is the reason I wouldn’t consider a poured retaining wall. 

 

 

[K78]

This is a good example. 

https://www.dezeen.com/2013/12/02/timber-clad-seaside-house-concrete-interior-ultra-architects/

 

[Alexphd1]

@TempI severely underestimated concrete before working with it but still surprised with that figure! 

 

Have a look at the basement expert website for DIY timber shuttering. 

Edited March 30, 2019 by Alexphd1

[K78]

1 hour ago, Alexphd1 said:

@TempI severely underestimated concrete before working with it but still surprised with that figure! 

 

Have a look at the basement expert website for DIY timber shuttering. 

 

I just checked that site out. It’s a good resource. 

 

I initially thought it would be as simple as this. I know this looks like a 70’s fireplace but I though the same method would work with timber  

 

If only ?

 

 

[Russell griffiths]

 

couple of things I think will make your idea fail. 

The product you use as the base coat, Portland cement won’t work, mix up a bag on its own and see how in workable it is,

you will need a bagged render product that has additional stuff to make it useable. 

Your mould size, there is no way you will be able to do an area bigger than a couple of m at a time. 

You will need to make 3-4 stamps and alternate them to get your pattern 

you will need a team of 3, 1 applying 1 stamping and 1 rushing around

i think the idea is feasible

but I personaly would do a feature wall not the whole house, it will look overpowering. 

 

 

[Temp]

I think that fireplace works because they apply a texture first then press in relatively sharp/low area grid lines. If you wanted to get a wood grain effect you would have to press in the larger area of a flat board. The force required would be a lot higher. I guess it might be possible to press in a small board? Give it a try.

[ToughButterCup]

15 hours ago, K78 said:

[...]

I will have bare durisol that will need to be plastered anyway. 

 

So do we.

 

I wish you every success - admire the fizz of your creativity. Try it small first. See what works, what breaks, what can be improved. I have very clear memories of my father supervising concrete shutter builds during the M5 and M6 construction (last century). He was one of the bridging engineers. The shuttering installations he helped design were massive. Working with the architect, he used to run small trials with different shuttering material.  Mostly WBP or planking. I remember one trial with raw planks of rough cut timber.

 

Even the trial installations were (relatively) massive. To keep me busy he made me help shovel concrete into the 'mould' . H+S would have a seizure if that were to happen  now...

[Nickfromwales]

47 minutes ago, BasementExpert said:

From a thermal mass point of view, beware of Durasol and polystyrene ICFs because the internal insulation is a huge barrier to storing and releasing heat quickly enough to reduce energy costs.

The whole point of these types of construction methods is to not require huge amounts of energy in the first place Agree the thermal retention is lessened re the walls, but who looks at storing and releasing energy to reduce heating costs in the context you suggest ( "quickly enough" )? In a Durisol / other ICF build, the mass you're referring to for energy stability is typically retained in all of the internal finish / fixtures / fabric layers not the core of the ICF.  

The 24 / 48 hr time period is what's important, so lets remember that heating up all that concrete in the first place, and then retaining the heat, takes equally huge amounts of energy ( which has to come from somewhere ). Having no requirement to inject that amount of heat in the first place = a low energy home. Add "mass" to add "thermal stability", but you still have to heat it and keep it there against it's will. Whatever kW of heat it emits will have required a greater amount to inject and retain it in order to facilitate that transaction, so concrete may be of benefit in certain targeted instances, but not in general, the same way an insulated passive standard UFH heated slab takes X amount of energy to stabilise it to ambient, then X amount more to keep it at ambint. To get the house heated from it then requires that original energy input plus whatever you require on top to maintain a comfortable temperature, plus losses. 

[K78]

The cheapest product I can find is shapecrete. Still too expensive to do on the scale I intended. 

 

It’s not really the colour I wanted anyway and I’m not sure why he bothers with the rubber?