Board concrete form moulds

[K78]

I’m trying to do as much of my build as possible to keep costs to a minimum. (Isolohr foundation, Durisol blocks or similar, Siberian larch exterior cladding)

 

I’ve been thinking about my interior walls. I’ve wanted concrete from the outset. 

 

The concrete effect plasters are ridiculously expensive, as are the wall panels. I’m also not a plasterer.

 

I have 2 joiners helping with my build. I was thinking of getting them to make floor to ceiling “moulds” out of 2” boards, that interlock together with 1cm wood block “spacers” on the front. 

 

I would cover the walls with Portland cement then drill the moulds to the walls while the cement is wet. The “spacers” would keep the cement depth consistent. 

 

Hopefully it would achieve a look similar to the attached pics?

 

Is this a terrible idea? 

 

Thoughts would be appreciated.

[Triassic]

Why not do a trial panel, if it look rubbish you could remove it.

 

Maybe fix an 8 x 4 sheet to the wall as a temporary backer and pour concrete against that as your trial peice. 

Edited March 29, 2019 by Triassic

[Mr Punter]

It is an interesting idea. The pictures look fantastic. I think it will be expensive and time consuming and if the finish is not spot on you will need to take it off and start again (or make the room 1" smaller!). If you get anywhere near a decent result I take my hat off to you.

[Sue B]

I think these pictures are stunning but I think a DIY version could be awful unless you (and your team) are real craftsmen, able to spend a lot of time creating the look.  I saw the Grand Design house a few months ago that had a concrete interior finish and I though it looked bloody awful and I fear a DIY version could easily head that way.

[K78]

Thanks for the replies. 

 

I think it would be time consuming but not so expensive compared to alternatives. Polished concrete walls look great but cost a fortune. Definitely not diy. A very skilled job

 

I would make 3 “moulds” that interlock together so that the pattern isn’t too uniform. As the wood grain in the boards forms the texture, I am thinking it would be relatively straight forward. Like vertical moulded drive. 

 

The finish doesnt have to be perfect. I love the texture of board formed retaining walls. 

Edited March 29, 2019 by K78

[jack]

I absolutely love that look and was disappointed it wasn't on the cards for our build.

 

It's definitely something I'll be insisting on for the next(!) one.

[Mr Punter]

Does anyone have a link to see how this is done in practice? I would be really interested to see how they make up the shutters, anchor them, construction joints, grout checks, concrete spec, how to pour and striking. I know how it is for casting a concrete wall, but facing an existing wall would be quite different.

[K78]

1 hour ago, Mr Punter said:

Does anyone have a link to see how this is done in practice? I would be really interested to see how they make up the shutters, anchor them, construction joints, grout checks, concrete spec, how to pour and striking. I know how it is for casting a concrete wall, but facing an existing wall would be quite different.

 

I think I maybe the first. I can’t see why it wouldn’t work.

 

The shutters are simple to construct and fix. I was planning to use Portland cement like plaster. Apply it thick, then fix the shuttering whilst it is wet. 

 

Can’t find anything on YouTube or a google search. 

 

Lots of examples of using rubber moulds for a brick/stone effect though. Similar to moulded concrete drives. 

 

 

[K78]

6 hours ago, Triassic said:

Why not do a trial panel, if it look rubbish you could remove it.

 

Maybe fix an 8 x 4 sheet to the wall as a temporary backer and pour concrete against that as your trial peice. 

 

That is what I plan to do. 

 

I just wanted to check if there was a obvious reason not too that I was missing. 

 

[Declan52]

Would it not be easier to plaster the wall like you do for a scratch coat then when you have it all nice and smooth use your mould and gently press into the  damp plaster to form the  impression. 

You would have to start at the top of the wall and work down only putting enough plaster on so it doesn't dry out too quick. 

[K78]

21 minutes ago, Declan52 said:

Would it not be easier to plaster the wall like you do for a scratch coat then when you have it all nice and smooth use your mould and gently press into the  damp plaster to form the  impression. 

You would have to start at the top of the wall and work down only putting enough plaster on so it doesn't dry out too quick. 

 

That is exactly what I plan to do. 

 

But the moulds will be floor to ceiling height, 3-4m wide and drill fixed with spacers until the cement goes off 2 or 3 at a time then repeat. 

 

The shuttering moulds would interlock like jigsaw pieces at both ends to give a seamless finished look. 

[Carrerahill]

12 hours ago, K78 said:

I’m trying to do as much of my build as possible to keep costs to a minimum. (Isolohr foundation, Durisol blocks or similar, Siberian larch exterior cladding)

 

I’ve been thinking about my interior walls. I’ve wanted concrete from the outset. 

 

The concrete effect plasters are ridiculously expensive, as are the wall panels. I’m also not a plasterer.

 

I have 2 joiners helping with my build. I was thinking of getting them to make floor to ceiling “moulds” out of 2” boards, that interlock together with 1cm wood block “spacers” on the front. 

 

I would cover the walls with Portland cement then drill the moulds to the walls while the cement is wet. The “spacers” would keep the cement depth consistent. 

 

Hopefully it would achieve a look similar to the attached pics?

 

Is this a terrible idea? 

 

Thoughts would be appreciated.

Can you not pour the walls you want to look like this in concrete with board forms?

[K78]

3 minutes ago, Carrerahill said:

Can you not pour the walls you want to look like this in concrete with board forms?

 

Im planning on doing my whole interior like this.

 

Im taking a diy approach. I’m not using a contractor. 2 joiners, 1 builder and 2 labourers will be helping. All on mates rates. 

 

Durisol or similar is the route I’m taking. I like the dry stack blocks. They make sense for my situation (unskilled idiot who can’t afford a building contractor) ?

[Declan52]

18 minutes ago, K78 said:

 

That is exactly what I plan to do. 

 

But the moulds will be floor to ceiling height, 3-4m wide and drill fixed with spacers until the cement goes off 2 or 3 at a time then repeat. 

 

The shuttering moulds would interlock like jigsaw pieces at both ends to give a seamless finished look. 

That would be a very heavy mould.  

Would it not be easier to just do one feature wall in this kind of finish like a wall with a wbs insert in it.  

I think the walls in your  pics have been from using timber shuttering rather than a mould. Which is a massive job in terms of skill and cost. 

 

[K78]

1 minute ago, Declan52 said:

That would be a very heavy mould.  

Would it not be easier to just do one feature wall in this kind of finish like a wall with a wbs insert in it.  

I think the walls in your  pics have been from using timber shuttering rather than a mould. Which is a massive job in terms of skill and cost. 

 

 

The moulds/shutters would just be lengths of 6” timber with batons on the back and spacers on the front. Thick coat of Portland directly onto the durisol, then drill through the spacers into the durisol to attach the shutters/moulds until the cement cures. 

 

It is really simple in my head. But I’m not explaining it very well.

 

I agree the walls in the pics are shuttered solid concrete

[Declan52]

6 minutes ago, K78 said:

 

The moulds/shutters would just be lengths of 6” timber with batons on the back and spacers on the front. Thick coat of Portland directly onto the durisol, then drill through the spacers into the durisol to attach the shutters/moulds until the cement cures. 

 

It is really simple in my head. But I’m not explaining it very well.

 

I agree the walls in the pics are shuttered solid concrete

You can't really put too thick a coat of plaster on or it will slip, start to slide down the wall and you get tear marks in it.  

A big square lump of timber approx 4m long by 2.5m high well be heavy. 

I think you would be as well doing a test panel and have a go and see what it looks like.  Then stand back and be honest. It's a look that when done well is stunning but if it's not. 

[Mr Punter]

I am with @Declan52 on this.  On the basis that there are no links to this, I don't think will work the way you are suggesting.  I thought that you were going to make single sided shuttering, fix it to the wall with spacers, pour the concrete in from the top and vibrate it with the poker on the face of the shutter.  I could not work out how you would get to the top bit though unless you left out the floor above until it was done.

[K78]

15 minutes ago, Mr Punter said:

I am with @Declan52 on this.  On the basis that there are no links to this, I don't think will work the way you are suggesting.  I thought that you were going to make single sided shuttering, fix it to the wall with spacers, pour the concrete in from the top and vibrate it with the poker on the face of the shutter.  I could not work out how you would get to the top bit though unless you left out the floor above until it was done.

 

I’d be open to that approach. If anything it’s easier and more diy friendly.

 

Would the concrete bond to durisol while curing, or would it need a base coat like a cement wash?

 

I’m not familiar with plaster and how it behaves, which is why I posted the thread. I was thinking I’d be able to apply a thick enough coat before I applied the shuttering. But as Declan says it will slide. Damn gravity. 

 

I’ve got 2 good joiners on site. My upper floor is open plan with a exposed roof structure. Shuttering would work well and I could still do it in sections to save on timber. 

 

I would be more of a challenge downstairs due to ceilings as you say. I’ll think of something else for downstairs. 

 

[PeterW]

I recon to stop any cracking you’re talking a 60-70mm layer of concrete at least. You could do 3 or 4 planks worth, fill and vibrate to get it to settle properly then move the planks up and go again when it’s set. Top one would need to be either done from above or as a cast “plank” that could be lifted into place and then grouted with a thin Portland mix as up above eye level wouldn’t be as visible. 

 

Not easy but admire you wanting to give it a go. 

[Alexphd1]

Why not just pour a concrete wall and add EWI ? 

[Temp]

 

14 hours ago, K78 said:

I have 2 joiners helping with my build. I was thinking of getting them to make floor to ceiling “moulds” out of 2” boards, that interlock together with 1cm wood block “spacers” on the front. 

 

Beware that any kind of form work for liquid concrete has to be very strong. The pressure at the bottom doesn't depend on the thickness of the concrete only the height. The density of concrete is high so the forces on formwork can be huge.

 

Manually pressing large areas/planks of wood into cement/plaster that is dry enough not to slump off the wall would also take a huge force.

 

 

[K78]

18 minutes ago, PeterW said:

I recon to stop any cracking you’re talking a 60-70mm layer of concrete at least. You could do 3 or 4 planks worth, fill and vibrate to get it to settle properly then move the planks up and go again when it’s set. Top one would need to be either done from above or as a cast “plank” that could be lifted into place and then grouted with a thin Portland mix as up above eye level wouldn’t be as visible. 

 

Not easy but admire you wanting to give it a go. 

 

That is a interesting idea.  I’m not scared of hard work. With the assistance of 2 joiners and 2 labourers I think it’s worth a go. 

 

8 minutes ago, Alexphd1 said:

Why not just pour a concrete wall and add EWI ? 

 

 Honest answer is cost. A shuttered concrete house would not be cheap and I honestly think the cost of EWI in the uk in nothing short of extortion.  It is ridiculous. 

 

I heard about a icf produuct where you can remove the inner leaf to expose the cured concrete. I imagine it is a lot more expensive and not as self builder friendly as durisol style blocks. 

[K78]

3 minutes ago, Temp said:

 

 

Beware that any kind of form work for liquid concrete has to be very strong. The pressure at the bottom doesn't depend on the thickness of the concrete only the height. The density of concrete is high so the forces on formwork can be huge.

 

Manually pressing large areas/planks of wood into cement/plaster that is dry enough not to slump off the wall would also take a huge force.

 

 

 

I think i would take peters advice and do it in stages. 

 

I appreciate its not as easy as I first thought. Thankfully my retaining wall nightmare has prepared me for almost anything. 

Edited March 29, 2019 by K78

[Mr Punter]

Given your lack of experience and the fact that this requires a very high level of skill and knowledge together with a great deal of time and materials I think you could be setting yourself up for failure.

[K78]

2 minutes ago, Mr Punter said:

Given your lack of experience and the fact that this requires a very high level of skill and knowledge together with a great deal of time and materials I think you could be setting yourself up for failure.

 

I appreciate your opinion. I mean that sincerely. 

 

But I don’t see where the high level or skill or knowledge are required. It’s not like I’m building a structural wall with shuttering and concrete. 

 

Its a basic concept unless I’m missing something?

 

If done in stages I can reuse the shuttering. So the timber cost won’t be huge.

 

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