Making my own formwork

[Triassic]

I'm due to start the digging out of our basement, it's set into a slope and once dug, it will be open at the front, onto a grassed area.

 

Having received some reduculous quotes for the basement walls, a mate suggests we get a locally recommended concreting company to cast the slab and he and I construct the basement formwork. He's just done some, as a  subbie, for a stand at the local football ground.  He suggests he and I could do the work for half the cheapest quote.

 

How hard can it be?  After all I have the structural engineers drawings to work to and millimetre accurate foundation drawings from Hilliard?

[Bitpipe]

I was amazed at the amount of work that our basement team put into the formwork construction.

 

The panels were very heavy duty (needed craned into position) and each one was custom made for the given pour, the steel threads & nuts that tied the panels together were also sizeable.

 

For reference, each pour was about 2.7m high and about 2-3m wide. Ridges were built into the end sections to leave channel grooves to take the water-bar for the next section.

 

Guys probably spent two days building the formwork for each pour (they did 2 sections simultaneously, a corner and a central panel).

 

Not saying that you and your mate are not competent but I guess it a question of materials, time and the cost (and liability) if any pours go wrong - either a burst or a wall that is not true or waterproof etc.

 

 

 

Edited September 8, 2017 by Bitpipe
Better pics

[Bitpipe]

[Triassic]

One of the problems I have and I know this is affecting the price, is no access onto site for a crane due to the topography. So the formwork will have to be constructed in-situ, out of parts that can be lifted using either a telehandler or muscle power. That's assuming the insulated slab is strong enough for to support a telehandler.

[Alexphd1]

 

maybe of a interest & they do have a agent in UK same guy i bought my ICF from.  For the record i have never used it but i do like the concept!

 

http://spidertie.com/

[Bitpipe]

34 minutes ago, Triassic said:

One of the problems I have and I know this is affecting the price, is no access onto site for a crane due to the topography. So the formwork will have to be constructed in-situ, out of parts that can be lifted using either a telehandler or muscle power. That's assuming the insulated slab is strong enough for to support a telehandler.

 

The slab (and kicker if you're doing it that way) itself should not need that much formwork, certainly none of the steel braces you see in my pic, as it will only be 200-300mm high. Once it's poured and cured then it should be able to take the load easy. 

 

It's the vertical elements that need the bracing, no reason why you cant build in situ, will just take longer I suspect.

 

Our guys built the corner (inc. window) and wall panels flat and then craned them around with some fine tuning for each pour. They could have torn them apart and remade for each pour if space was tight but it would have taken much longer. 

Edited September 8, 2017 by Bitpipe

[Russell griffiths]

Any reason you are not using icf, this is what I would do

light weight to move about easy to add the reo, many approved systems for waterproofing. 

 

The time you buy all that ply just to form it up then you take the formers down and you still need to insulate the walls your left with. 

 

I would be interested to know @Triassic why you are not doing icf. 

[Russell griffiths]

Are you doing your slab yourself ?  

[mvincentd]

As Bitpite suggests, do not underestimate the complexity of shuttering and the heavy duty-ness of it.

Part of my construction was 'single-sided' shuttering.....in other words too near a boundary for them to be able to form their usual shuttering so I had to create a sacrificial face to cast against.  I used 18mm osb on vertical 4x2's which i concreted into the ground....then I added horizontal 4x2's...then i chocked it against the chalk face with more wood...and added more bracing where I could.  The rc guys just laughed...well, rolled their eyes.  When we'd done all we could with wood they added metal soldiers to tie my rear shutter to their front shutter....then they added huge diagonal push-pulls so they could wind the whole structure back during the pour to keep it vertical.  Their front shutters are also held in place by captive bolts  that were cast into the kicker along with the slab...helping to fight the lifting forces that the poured concrete exert on the shuttering.  This is the tip of the iceberg as far as the complexity and intricacy of the shuttering work goes.

They were on a fixed price...i don't think they'd do all this stuff if it wasn't necessary.

One of my vertical 4x2's still snapped during the pour, thankfully to no significant effect.

 

[Triassic]

12 hours ago, Russell griffiths said:

Any reason you are not using icf, this is what I would do

light weight to move about easy to add the reo, many approved systems for waterproofing. 

 

The time you buy all that ply just to form it up then you take the formers down and you still need to insulate the walls your left with. 

 

I would be interested to know @Triassic why you are not doing icf. 

My self build project has been a bit of a stop start affair over the last couple of years. We started planning with great gusto when we had a buyer for our house, unfortunatly the sales chain fell through and it was all stop. Then the original buyer came back again last year and we finally sold our old house. So we moved onto site and have been slowly picking up where we left off. We've only looked at formwork as this is the approach suggested by the last two builder we had on site to look at and quote for the work. Their quotes were so far apart, £50k and £150k I was left scratching my head!

 

As to ICF, it's something we looked in the past, but I have no experience of it. Maybe I need to consider it again.

[Triassic]

12 hours ago, Russell griffiths said:

Are you doing your slab yourself ?  

I'm talking to a local concreting contractor to do the slab. He specialises in concrete slabs, he has his own concrete pump, something we will need as we can't get a mixer truck onto site. The truck can only reverse off the road to discharge into the pump. The concrete will then be pumped onto site.

 

 

[Simplysimon]

@Triassic, i'm sure you're aware, as the formwork goes higher the pressure at the bottom increase. if you do it yourself you will need steel formwork, yes it can be done with timber as @mvincentd did and has been done for years before steel came along, but it is a big job, and shuttering is a specialised trade. if it were me i'd go with icf, shutter it and insulate it in one go.

 

simon

[iSelfBuild]

Have you considered precast concrete? - http://fpmccann.co.uk/precast-concrete/walling/l-walls

 

I haven't consulted my engineers yet for my next walk out basement build... but no way am I doing it the last way with blocks etc! I might even make my own insulated forms with insulation pins and make a climber form work which I can anchor into the already cast concrete and climb it up every 800mm pour.

[Jeremy Harris]

41 minutes ago, iSelfBuild said:

Have you considered precast concrete? - http://fpmccann.co.uk/precast-concrete/walling/l-walls

 

I haven't consulted my engineers yet for my next walk out basement build... but no way am I doing it the last way with blocks etc! I might even make my own insulated forms with insulation pins and make a climber form work which I can anchor into the already cast concrete and climb it up every 800mm pour.

 

I looked at these for our retaining wall, at the suggestion of a local farmer.  For us, the only downside was getting a big enough crane on site for the 2.5m high sections we needed.  For us the base foundation and anti-slip key was pretty easy, just a trench foundation along the base for the pre-cast sections, keyed with a deep slot, floated level and the L shaped sections just bolted into place on top of it.  There wasn't much difference in cost between using the precast sections and building a hollow block concrete filled and reinforced wall, but the precast option would have saved around two weeks in build time, I think.

[SteamyTea]

We used to make decorative moulds for concrete formwork.  I was quite surprised just how ridge they were made.  Large RSJs and very large timbers.

 

 

[Jeremy Harris]

14 minutes ago, SteamyTea said:

We used to make decorative moulds for concrete formwork.  I was quite surprised just how ridge they were made.  Large RSJs and very large timbers.

 

 

 

The most impressive ones I've seen were at a place a friend worked, that made cast concrete staircases, with a highly polished finish.  They used strongly reinforced plate glass moulds, with a two-part casting process, where the finish coat was applied to the glass, allowed to partly cure, then the structural layer was cast.  The glass moulds were works of art.  The place still exists, Cornish Concrete Products, but at the time my friend worked for them most of their business was in the Middle East, so he was based semi-permanently in Dubai.

[Triassic]

So if I went down the ICF route, which product is the best, in terms of easy of use and value for money etc?

[ToughButterCup]

Well, @mvincentd, yours makes my little foray into concrete shuttering look very very tame indeed. 

 

Your photos seem to show a project more akin to a civil engineering. I'd be interested to see what you plan... Our shuttered pour had me feeling sick with worry about the consequences of a burst - where at worst I'd lose a cube of concrete. 

 

@Triassic, I know a bit about Durisol: as I understand it we don't live all that far apart. J33 on the M6 for me. So why dont you pop round - you could at the very least count Durisol out on the basis of evidence.

[Triassic]

17 minutes ago, recoveringacademic said:

 

 

@Triassic, I know a bit about Durisol: as I understand it we don't live all that far apart. J33 on the M6 for me. So why dont you pop round - you could at the very least count Durisol out on the basis of evidence.

 Now that I'm getting back the full swing of self Build, I'll take you up on that offer. I'm busy this week, so maybe sometime next week if possible.

 

 

[PeterW]

Polarwall, Nudura and Beco are pretty much the only ones I've seen with decent technical credentials for basements although Beco seem to be fallout by the wayside. 

 

The others can have variable core widths to allow for structural support to be correctly calculated. 

[Triassic]

8 minutes ago, PeterW said:

Polarwall, Nudura and Beco are pretty much the only ones I've seen with decent technical credentials for basements although Beco seem to be fallout by the wayside. 

 

The others can have variable core widths to allow for structural support to be correctly calculated. 

The SE has calculated a core width of 200mm, I assume I just send my drawings to the ICF companies, along with Insulation requirements and they do the rest.

[Alexphd1]

We used nudara and as long as there still price competitive we will be using them again in build 2.

[ToughButterCup]

36 minutes ago, Triassic said:

 Now that I'm getting back the full swing of self Build, I'll take you up on that offer. I'm busy this week, so maybe sometime next week if possible

 

PM me. I'm around most of the time.

[jamiehamy]

14 minutes ago, Triassic said:

The SE has calculated a core width of 200mm, I assume I just send my drawings to the ICF companies, along with Insulation requirements and they do the rest.

Pretty much. Has the engineer provided the details of the reinforcements? Or just a 200mm core? 

 

We've just about finished our garage walls with mesh up inside the 250mm core. Was very straightforward. Rather than try build with mesh itself,  we used rebar and tied it as we went up. The slowest part was the tying - lesson for next time is to hire or by a tool for it as it was very slow. 

 

Attached pic shows how we did it - braced from inside. We had rebar sticking out the slab 500mm.  I put. down three courses of Polarwall before sticking the vertical bars in and tying. Then we laid bars on each course of icf ties as we went up. The ladders slipped over the top of the rebar and down. Financed permitting we will pour in the next few weeks. 

[jamiehamy]

Pic of rebar detail.