Nudura Cast-in-Place Ledgers....

[Mulberry View]

For those interested, here is how I installed my Timber Ledgers before my pour....

 

I used 9x2 TR26 boards, ripped down to 206mm to dimensionally match my 253mm Posi by the time they are top chord hung on the Ledgers.

 

I first installed 4x2 Timbers to the wall where the Nudura props would go with hefty 6.7mm Timber Screws. The Prop channels were screwed on top of the timber using normal Nudura screws. The 4x2's were deliberately 200mm or so shorter than the Nudura channels, creating a pocket in which to slot the Ledger timber. Like this...

 

 

Once this was done, I marked the top and bottom of the Ledger and planned the positions of the bolt fixings according to engineers spec (in my case no greater than 800mm, but also planned to suit the blocks and various other considerations. Pockets were then cut, with a 45° draft at the top and bottom to aid concrete flow.

 

 

More to follow....

[Mulberry View]

Once this was done, I used a jig I made to drill the M16 holes in the Ledger, 65mm from top and bottom according to SE spec.

 

 

 

 

 

[Mulberry View]

This is a beam with the bolts in place. You'll see some toothed Timber Connectors. These were specified by my Engineer and were added to both stud positions in the end. The bolts were removed for installation of the beam in order to slot it into place. Once they were in place, I attached a large square washer with a double nut to the part that would sit in the core as an anchor.

 

 

This is the view from inside the Nudura form, looking into the pocket from the rear.

 

Edited January 16 by Mulberry View

[Mulberry View]

Finally, I added a small piece of 4x1 and a single woodscrew to hold the bolts in place and prevent them pushing out when the concrete went in. The Ledger was levelled and secured with the 6.7mm Timber Screws, but was fairly tightly in place behind the props anyway.

 

 

The concrete is now in and once it has fully cured, I'll go round and cram the nuts up. As an additional bonus, I think the Ledgers helped keep the wall nice and straight.

 

Hope this helps someone out!

[WiltshireLink]

so did you have the ledger in place for pour or just the bolts held in with some temporary wood?

[Mulberry View]

1 hour ago, WiltshireLink said:

so did you have the ledger in place for pour or just the bolts held in with some temporary wood?

 

What you see in the final picture is how we went into the pour. Ledgers in place.

[WiltshireLink]

sorry to be thick, but why have you put 4x1 on the outside? Is that over the bolt to stop it being pushed out during pour? I was thinking of putting the ledger in before pour but advised it means setting up the prop system becomes more fiddly!

[ChrisJ]

Were you advised to put some form of a break/separation between the back of the wood where it touches the concrete, such as peel & stick? 

[WiltshireLink]

No, not advised to do that 

[Mulberry View]

Me neither. For what purpose?

[Mulberry View]

As an update to this, I have been round with a laser level and can confirm that the Ledgers are at +/-2mm from their design height. Pretty much as they were before the pour.

 

The only thing I would do differently if I did it again would be to add more timber screws to fix the Ledger to the ICF blocks. Although the Ledger was 'trapped' behind the props, in some places the blocks pushed away by a couple of mm. This won't cause an issue, but the timber screws would have prevented this.

[ChrisJ]

Concrete and wood should not 

On 18/01/2024 at 16:08, WiltshireLink said:

No, not advised to do that 

 

On 18/01/2024 at 23:09, Mulberry View said:

Me neither. For what purpose?

 Wood and Concrete should not touch, even once concrete has cured. May not be a code issue or requirement here in the UK, but I have seen wood rot sooner rather then later from touching concrete, even Green Treated lumber will start to fail

[Mr Punter]

13 minutes ago, ChrisJ said:

Wood and Concrete should not touch, even once concrete has cured. May not be a code issue or requirement here in the UK, but I have seen wood rot sooner rather then later from touching concrete, even Green Treated lumber will start to fail

 

It is only an issue if the concrete remains damp.

[Chanmenie]

4 hours ago, Mr Punter said:

 

It is only an issue if the concrete remains damp.

Which it should not do as the concrete ends up inside the house and will have DPM at the base.

[ChrisJ]

Like I say, maybe not a code requirement in the UK, but keep in mind wood is organic and a sponge it will suck the moisture from the concrete and good potential for rot to occur. This is why I prefer the Simpson ICF hangers for my rim boards, but when doing exposed connections I would use peel & stick membrane on the backside of the rim board to separate the 2 products

[FM2015]

This just seems like a massive waste of time to save a few quid to get to an end position easily achieved using existing, certified methods, whilst potentially introducing risk into the pour element.

 

Sorry.  Might be missing something.

[Mulberry View]

Posis are now on site. It is a simple design, this part of the building is rectangular, so the Posis fully span the width.

 

One of the great things about doing it this way is that the 13.5m long walls were held not only with the props, but with the Ledgers too, so remained very straight. When I surveyed the width along the full length after the concrete had cured, I was a couple of millimetres out from the target measurement.

 

We got the Posis up into position quickly, these are not fully fitted yet. These ones are 47x97 at 400mm spacings. The next bay to go up are 47x147, again at 400mm spacing as this is the Master Ensuite, which is to have a large bath. (these are now up, but not photographed).

 

 

 

 

[Mulberry View]

The Posi design included a tolerance gap below the Top Chord. This was not requested by me, but I ended up utilising it to deal with any clashes of Ledger fixings. I was able to plan the fixings to miss the Posi positions until I got half way along, where there was an irregular gap due to an internal wall position, but it didn't really matter.

 

 

I planned the MVHR exhaust and inlet to fall within a 300mm gap between 2 Posis. These went through before the concrete and ended up as I intended.

 

 

There is another of these on the opposing wall. They both head towards each other, the drop down into the plant room, either side of the Strongback, which doesn't interfere.

 

I'm planning to infill between the joists with 47x50mm CLS, which I will cut to 300mm lengths to help me space the joists consistently.

 

How should I fix the Posis to the Ledger? I'm thinking 2no 5x80mm screws in each, predrilled downwards through the top chord into the Ledger?

[ChrisJ]

Unless you're planning to purchase the expensive structural screws I would just use 90mm nails in my nail gun to secure the joists down. a little trick it to also use a dap of GripFill or even spray foam between the joist and the ledger, this will help prevent any potential squeaks as the floor will flex and move slightly. May not be a big issue with wood on wood, but if you had joist hangers it makes a huge difference, lets put it this way for the few pence it costs I'd be doing it, same with your filler piece (47x50) that will be used as solid blocking for a fully nailed diaphragm of the floor, don't forget to use GripFill or spray foam when you place your sheathing down either - makes the floor a bit more solid and prevents squeaks

[Dave Dunker]

For your timber ledgers try the Burmon System https://www.icf-fix.co.uk/c/products

[Mulberry View]

On 10/03/2024 at 09:12, Dave Dunker said:

For your timber ledgers try the Burmon System https://www.icf-fix.co.uk/c/products

 

Yes, these look good, but expensive. I'm pretty happy with how my Ledgers went in for the lower level, I'm hoping to do the same for the upper deck (roof), with the learnings from the first time.