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Stones    315

Following a comment from @Nickfromwales about once being asked by a QS to fill stud voids with plasterboard offcuts to reduce waste disposal costs, thought it would be interesting to discuss the pros and cons of doing so.

 

What are everyone's thoughts? I can see the rationale for doing this on cost grounds, and the possible sound deadening benefits if using whole pieces well fitted into the void.

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Nickfromwales    941

According to @JSHarris's comments, PB actually has good thermal absorption and retention qualities ( worded badly by me but you get the drift ) so once the shock and horror of the suggestion wears off it may not be so bad at all. 

It would definitely make acoustics better, for sound deadening, and if you bonded it with foam where it was needed you'd be able to use double depth plasterboard fixings to hang heavy equipment. 

Just the suggestion seemed a bit 'cowboy' to me at the time, so I didn't do it. 

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ProDave    660

In our last house, we left 2 trap doors to access the under floor void (air tightness was not on my agenda then, there are no trap doors in the new house)

 

Under the floor we put all the spare and even the offcuts of all the floor and wall tiles used. Partly as somewhere to keep them in case a spare was ever needed and partly to save carting a load of heavy stuff to the tip.

 

Spare PB in a wall cavity would be okay as long as it's packed tight. Loose bits may "rattle " if someone bangs the wall?  If I were to do something like that, it won't be until the end of the job, and then they would probably go in the garage walls, rather than in any of the internal house walls.

 

On a related subject, another self builder here had loads and loads of offcuts of insulation batts. He was going to take them to the tip in several trips in his car.  They are now in my garage. They are all too small to be of any use for wall insulation (to small to wedge them in place) but will make perfect under floor insulation in my sun room, filled from above before the floor goes down.  It's good to use someone else waste and save money at the same time.

 

I think what @Nickfromwales was trying to describe was T*****L M**S :ph34r:

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JSHarris    869

Plasterboard has a higher mass heat capacity than concrete, so if it's located where that might be useful, say in terms of increasing decrement delay, then it would be useful.  In fact, if you want to improve the heat capacity of the internal structure of the house, double boarding a timber frame with plasterboard will probably do a better job than having block walls.  Only around the first 100mm, if that, of external wall thickness has any appreciable effect, usually, in terms of storing useful heat over the range that may help keep the house internal temperature stable.  The higher the heat capacity of the inner layer the better, and plasterboard has a mass heat capacity that is around 23% higher than concrete.  It's one of the points that illustrates how daft the false notion of "thermal mass" is.  The implication with this unmeasurable property is that mass = heat capacity, which is nonsense. 

 

1kg of brick has a heat capacity of around 840 J.kg.K

1kg of concrete has a heat capacity of around 880 J.kg.K

1kg of gypsum plasterboard has a heat capacity of around 1090 J.kg.K

1kg of wood (or compressed wood fibre) has a heat capacity of around 1200 to 2900 J.kg.K

1kg of water has a heat capacity of around 4181 J.kg.K

 

In the above list, the higher then number, the greater the amount of heat the material will store for a given temperature change.

 

In other words, if you want to store heat in a building in order to help stabilise its internal temperature, by increasing the mass of the building, then you're better off using something other than brick of concrete, as on a heat stored per unit mass basis brick or concrete is far from being very useful, lightweight concrete even less so. 

 

Edited by JSHarris
Typos. "that" and "than" swapped
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Crofter    251

So should we all be buying big room-temperature fish tanks and putting them around our houses, to act as thermal stabilisers?

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Nickfromwales    941
21 minutes ago, Crofter said:

So should we all be buying big room-temperature fish tanks and putting them around our houses, to act as thermal stabilisers?

No. we should be collecting every scrap bit of PB we can and burying it in our houses to retain heat and stabilise our heating systems. 

 

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ProDave    660

So before fixing your last sheet of PB, collect all your offcuts and stick them mosaic fashion to the back of the last board using some sticks like s*it or similar.

 

If you want to do this yourself, look out for all my offcuts for sale in the market place soon, only a little bit more than buying a new sheet :ph34r: (my dad once asked a builders merchant why it was that crazy paving cost more than whole paving slabs, the reply was to pay for the time it took to break them up.)

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JSHarris    869
1 hour ago, Crofter said:

So should we all be buying big room-temperature fish tanks and putting them around our houses, to act as thermal stabilisers?

 

 

It's been done, well, almost! 

 

I saw one house design, in Germany I think, that had a helical staircase running up the centre of the house.  The core of this was a massive cylindrical water tank - I can't remember the volume but it was many thousands of litres.  It was insulated, to allow it to remain much warmer than the house, and used as a massive storage heater for low grade heat, effectively working as an absolutely massive buffer tank to run an UFH system, IIRC.  I can't recall the performance, but seem to recall that the tank could heat the house for a couple of months or so without having any energy input to it.

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Onoff    730

Could waste pb conceivably go into the oversite layer of another building?

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JSHarris    869
1 minute ago, Onoff said:

Could waste pb conceivably go into the oversite layer of another building?

 

It's best kept out of the ground, because of some of the reactions that gypsum can create with other substances in the ground, but would be OK as dry fill somewhere where it can't cause a problem.

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ProDave    660

My plumber friend just dug a hole and burried all his offcuts.......

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Onoff    730
47 minutes ago, JSHarris said:

 

It's best kept out of the ground, because of some of the reactions that gypsum can create with other substances in the ground, but would be OK as dry fill somewhere where it can't cause a problem.

 

So could you lay say sub base, EPS, DPM then waste pb followed by PIR?

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Ferdinand    413

Is there any device that would shred plasterboard before it was used for soil neutralisation?

 

I wondered about a timber shredder, but given what it does to Stanley knives I think the shredder would be the thing that was shredded.

 

Cut into strips perhaps and then break like sticks?


F

 

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Onoff    730
6 minutes ago, Ferdinand said:

Is there any device that would shred plasterboard before it was used for soil neutralisation?

 

I wondered about a timber shredder, but given what it does to Stanley knives I think the shredder would be the thing that was shredded.

 

Cut into strips perhaps and then break like sticks?


F

 

 

That's what I was half getting at. For some reason I thought it could actually be GOOD for the soil?

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JSHarris    869

The main problem with burying plasterboard is that the gypsum will breakdown into sulphides, and particularly hydrogen sulphide, (the "rotten eggs" gas) when other organic materials in the soil are present.  H2S is detectable at very low concentrations, well below the level where it becomes toxic, but it is a nuisance, and is one reason that plasterboard is recycled rather than sent for landfill.

 

Having a buried pile of plasterboard in the garden, or under the house, that releases H2S  for many years could make your house a pretty unpleasant place to live.

Edited by JSHarris

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Ferdinand    413
11 minutes ago, Onoff said:

 

That's what I was half getting at. For some reason I thought it could actually be GOOD for the soil?

 

Farmers' conversation: (*)

http://www.fwi.co.uk/community/topic/gypsum-from-re-cycled-plasterboard/

 

I think it is to do with the types of plasterboard you use, how you pulverise it, and putting it in the top layer as a conditionner rather than down a deep hole.

 

(*) Loving:

Quote

I’ve just parked my 10 ton spreader next to my 2000 ton mountain of gypsum, and I’ve realised I’ve got quite a daunting job on my hands! It might make more sense to keep it as a skiing resort!!

 

Edited by Ferdinand

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Onoff    730

Seems it can be soil type dependent as to whether plaster board will be of benefit if ploughed in...

 

 

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Stones    315
6 hours ago, Onoff said:

 

That's what I was half getting at. For some reason I thought it could actually be GOOD for the soil?

 

It's certainly been argued:

 

http://www.darlingtonandstocktontimes.co.uk/news/10742945.Plasterboard__used_for_cattle_bedding___Darlington_skip_hire_firm_trial_told/

 

I think we had a few sheets worth of scrap / odd size pieces that were unlikely to be of use elsewhere so got disposed of.  It never occurred to me to use them between studs, but I think I would only want to do so if they were fitted tightly, i.e. not just a collection of rubble.

 

I have to admit to liberating various things out of the skip which I thought may be of use to me, but were of a size / quantity as to be worthless to the builder. What pained me most was the offcuts of polystyrene ICF block that resulted from building the pitched section of the gable walls.  I just couldn't come up with a use for the triangular shaped pieces.

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Ferdinand    413
3 hours ago, Stones said:

 

It's certainly been argued:

 

http://www.darlingtonandstocktontimes.co.uk/news/10742945.Plasterboard__used_for_cattle_bedding___Darlington_skip_hire_firm_trial_told/

 

I think we had a few sheets worth of scrap / odd size pieces that were unlikely to be of use elsewhere so got disposed of.  It never occurred to me to use them between studs, but I think I would only want to do so if they were fitted tightly, i.e. not just a collection of rubble.

 

I have to admit to liberating various things out of the skip which I thought may be of use to me, but were of a size / quantity as to be worthless to the builder. What pained me most was the offcuts of polystyrene ICF block that resulted from building the pitched section of the gable walls.  I just couldn't come up with a use for the triangular shaped pieces.

 

Pyramid made using icf.

 

Your Egyptian tomb if this is your literal forever house.

Edited by Ferdinand

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