Beam & Block systems with insulative blocks - when do or don't they make sense?

[lineweight]

10 hours ago, Nickfromwales said:

 

 

I prefer products like Beam-shield, where the sections tuck under the beam and contact the preceding block. So when you look at the underside, you cannot see anything other than EPS.

Thanks, I had not come across this option before. I can see that it potentially lets you use the beams and the screed layer as thermal mass as they can effectively be "warm" inside the insulation envelope.

 

Do you have any experience of how it ends up comparing cost-wise with a conventional b&b buildup?

[saveasteading]

Costs more of course as the blocks are fancy compared to normal cuboid ones. 

 

It is very clever and may avoid or reduce  putting pir over the floor.

[bassanclan]

15 hours ago, lineweight said:

What makes it more costly - the bits you buy from Jetfloor?

 

The bits you buy from Jetfloor are more expensive. A shaped section of eps is always going to be more than standard 8x4 sheets.

Also, you can't shop around so much for the concrete beams as you have to buy the whole Jetfloor system.

Also Agilia concrete is more expensive than standard concrete and needed a pump.

 

No issues with cracking. Went in the next day after pouring and cut breaks in natural places,e.g. across doorways etc.

[bassanclan]

15 hours ago, lineweight said:

 

Edited April 11, 2023 by bassanclan

[bassanclan]

The first time you buy Agilia you get site service. Subsequent times you are expected to know what you are doing which is why you might have had problems 50 percent of the time?

[Dave Jones]

i looked at these last build, the problem with them is it makes you screed the floor before the walls go up as they are not a workable surface for loading out. So you have to get underfloor etc all in before the roofs on which doesnt work.

 

maybe a shed build where roof goes on quick they could work.

[bassanclan]

4 hours ago, Dave Jones said:

i looked at these last build, the problem with them is it makes you screed the floor before the walls go up as they are not a workable surface for loading out. So you have to get underfloor etc all in before the roofs on which doesnt work.

 

maybe a shed build where roof goes on quick they could work.

No screed, just a single layer of structural concrete.

Leave to set for a few days then put a few sheets of plywood on for extra protection, but yes it does mean ufh pipes need to be in at an earlier stage than otherwise would be the case

[Canski]

Our last site was poured on the Friday and we were working on the floors on the Monday. Same as oversite concrete but due to less thickness it goes off quicker. 

[Rishard]

23 hours ago, saveasteading said:

Beam and block comfortably spans 4m.

Polishing the slab is ok, but a bit specialist for domestic. I prefer concrete screed, pir, screed with ufh. Control.

 

Or b and b, then pir and screed.

 

150 slab with 1 bottom layer of mesh is a surprise as a suspended slab. That will require great precision. 

 

 Crack control is simple enough. For later discussion.

The 4m span is the reduced span due to adding a dwarfwall/footing to help with either b&b or suspended slab. I poured a raft for my double garage on the same site and polished the slab as a test run. It worked well and so far no issues. My plan was to polish the main house floor with the aim to reduce the need for both a slab and a screed. I see this may be harder to achieve now but hopefully not impossible. I’m now looking at the Golcar ph slab design, only difference being the void formers in my case. My engineer spec’d the slab reinforcement so I don’t have too much concern regarding the mesh detail, however this isn’t my specialism and I trust he would be confident in his own design. Which details do you think would require great precision? If it’s just one layer of mesh to the base I think the mesh would be a lot easier than jobs I’ve done with several layers/hystools /overlap build ups. 
 

Aiming for ph levels of insulation with mvhr, 3G ect. Wouldn’t  a 150mm slab with underfloor heating be better suited than a screed for storing more heat? Happy to change design if I foresee the slab finish not being achievable. 
 

22 hours ago, lineweight said:

Presumably it depends whether the void formers are the type that are designed to disintegrate? If they are to deal with ground heave then presumably they are - in which case wouldn't you end up with an airspace of some kind under the slab?

I have been looking at the jablite void formers which look to simply compress when the ground does heave. I don’t like the look of the ‘just add water’ ones to create a void. I see the Jablite ones as ground baring up until the ground moves, if it moves. Once the soil heaves, does it retract at all? 
 

Although we have ‘medium’ shrinkage clay, the void formers are being used to overcome being close to where we had an old, now removed pear tree. All spec being followed directly from nhbc guidelines. 
 

Edited April 12, 2023 by Rishard

[lineweight]

14 minutes ago, Rishard said:

I have been looking at the jablite void formers which look to simply compress when the ground does heave. I don’t like the look of the ‘just add water’ ones to create a void. I see the Jablite ones as ground baring up until the ground moves, if it moves. Once the soil heaves, does it retract at all? 
 

Although we have ‘medium’ shrinkage clay, the void formers are being used to overcome being close to where we had an old, now removed pear tree. All spec being followed directly from nhbc guidelines. 

I'm not a particular expert on this but I think you would have to allow for the possibility that it could shrink again. I think the process can occur to some extent on a seasonal cycle as the amount of water in the ground increases and decreases.

 

With a suspended slab are you still obliged to provide ventilation to the cavity underneath?

[lineweight]

15 hours ago, Dave Jones said:

i looked at these last build, the problem with them is it makes you screed the floor before the walls go up as they are not a workable surface for loading out. So you have to get underfloor etc all in before the roofs on which doesnt work.

 

maybe a shed build where roof goes on quick they could work.

 

You mean internal partitions I guess? You can carry on building up external walls and loadbearing internal walls, can't you, before the screed goes in?

[Rishard]

5 minutes ago, lineweight said:

I'm not a particular expert on this but I think you would have to allow for the possibility that it could shrink again. I think the process can occur to some extent on a seasonal cycle as the amount of water in the ground increases and decreases.

 

With a suspended slab are you still obliged to provide ventilation to the cavity underneath?

I’m not sure about the air space below a void formed suspended slab. Hopefully someone on here knows… I’m about to crunch some numbers on supply only for both b&b vs void formed slab so will post my results. 

[saveasteading]

1 hour ago, Rishard said:

great precision? 

Assuming this slab is designed as structural, ie self supporting, then the reinforcement must be positioned precisely as instructed, ie distance off the bottom. Then concrete quality and compaction. This is not stuff that most groundworkers do, or even know about.

 

And one layer of bottom mesh is unusual in a structural slab. I'd expect some top as well.

 

It all seems strange and I feel this is not the whole story. Drawings?

Edited April 12, 2023 by saveasteading

[Rishard]

8 hours ago, saveasteading said:

Assuming this slab is designed as structural, ie self supporting, then the reinforcement must be positioned precisely as instructed, ie distance off the bottom. Then concrete quality and compaction. This is not stuff that most groundworkers do, or even know about.

 

And one layer of bottom mesh is unusual in a structural slab. I'd expect some top as well.

 

It all seems strange and I feel this is not the whole story. Drawings?

I can send you my engineers annotated plans which he put together for me for the sake of a costing exercise. His final calculations are on going with some of the other calculations for the house. He did recommend some mesh to the top of the slab but like I said previously, only in a few places where there would be hogging moments (I believe he called them) 

[saveasteading]

Up to you. I don't expect any errors in the calculations. It's more about understanding the whole scenario. Anything from your consultants should anonymise who they are.

 

I was thinking about quality. Having worked on major structural concrete projects, then come across the typical groundworker, they are not remotely the same.

With my own money I use the normal groundworker but have to supervise.

I have seen them variuosly leave drink tins on the bottom about to be concreted in, add masses of water to concrete, stamp mesh down to the bottom,  not lap the mesh, bodge drains with silicon, refill overdug excavations......

Some of them don't take instruction willingly.

I am seeing on BH why an SE might overdesign a bit....knowing it is likely to be badly built

[Canski]

I had two identical floors poured on Thursday. Both with Agila 75 mm thick with fibres. The first was fine but the lads struggled with the second due to the heat and the concrete going off very quickly. It was a separate load of concrete for each floor. The second floor is riddled with cracks. I’m not a happy bunny. 

[Dave Jones]

On 25/08/2023 at 20:20, Canski said:

I had two identical floors poured on Thursday. Both with Agila 75 mm thick with fibres. The first was fine but the lads struggled with the second due to the heat and the concrete going off very quickly. It was a separate load of concrete for each floor. The second floor is riddled with cracks. I’m not a happy bunny. 

 

traditional screed for me every time.

[Canski]

2 hours ago, Dave Jones said:

 

traditional screed for me every time.

Doesn’t work as a structural topping unfortunately. 

[saveasteading]

On 25/08/2023 at 20:20, Canski said:

second floor is riddled with cracks. 

They probably added water to keep it fluid. That then evaporates leaving the equivalent amount of aero type voids and weakness.

I don't know the product. But ready-mixed suppliers will require a signature on the ticket before adding water. ...because it is a bad thing.

Did you buy it or your contractor? Either way, the delivery ticket will say.

 

It isn't disastrous. This happens with all concrete in hot climates.

 

Photo?

 

 

[Dave Jones]

2 hours ago, Canski said:

Doesn’t work as a structural topping unfortunately. 

 

yeah you build the walls before screeding etc.

[Canski]

38 minutes ago, Dave Jones said:

 

yeah you build the walls before screeding etc.

and it still wouldn't work on an insulated beam and block floor

[Canski]

45 minutes ago, saveasteading said:

They probably added water to keep it fluid. That then evaporates leaving the equivalent amount of aero type voids and weakness.

I don't know the product. But ready-mixed suppliers will require a signature on the ticket before adding water. ...because it is a bad thing.

Did you buy it or your contractor? Either way, the delivery ticket will say.

 

It isn't disastrous. This happens with all concrete in hot climates.

 

Photo?

 

[saveasteading]

First I'd ask the contactor what they think about it. Prediction....its normal.

Then see thd delivery tickets.

 

What's underneath determines whether this is a problem or inconvenience.

[Canski]

14 minutes ago, saveasteading said:

First I'd ask the contactor what they think about it. Prediction....its normal.

Then see thd delivery tickets.

 

What's underneath determines whether this is a problem or inconvenience.

Thanks. Yes I have asked for the delivery receipts and asked them to pop out and take a look.

 

Underneath is a beam and insulated block floor. Litecast GT12

[Dave Jones]

15 hours ago, Canski said:

and it still wouldn't work on an insulated beam and block floor

 

sure it would, sleeper walls etc. still wouldn't bother with them with the massive built in thermal bridging, double/treble the price of a standard floor and only benefit is saving a couple muck always.