New Build - Floor insulation Qs

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Birroc

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Hi,

Whats involved in putting down floor insulation before the screed is laid ?
I presume I have to sweep up all the dirt/dust, put down the Kingspan (100mm) and cut around the plumbing pipes. Should I tape the Kingspan sheets together ? Anything else ?

What plastic do I put on top of the Kinspan ? Just normal polythene ?
 
No need for plastic on top of your Kingspan. might tape together if you think it will be windy but the screed will soon take care of that. A few blocks maybe too just to weigh it down so the screed doesn't move it..

Best of luck
 
Hi Birroc,

We are putting down our floor insulation this weekend -going to scrape and clean the floor first and then put down the insulation - we are going to put plastic cover over it - the screed can react with the insulation and most screed companies will ask you to put plastic down over the insulation and under the underfloor heating pipes!

We are putting clear 500 gauge ploythene over the insulation.

:)
 
There is no need to tape the joints. However the insulation should be tightly butted together. If there are any gaps such as around pipes or where a sheet got damaged fill these with expanding foam. You should also use perimeter strips at the edges where the slab meets external walls (some people recommend the same for internal walls, depending how serious you are about the job). These strips are about 6 inches high and 1 inch thick.

It is not standard practice to place plastic over the insulation. However, it is now increasing common to hear people recommending this as it prevents the foil lining/insulation/concrete from reacting over time. Normal polythene sheeting should do, but I have also heard of some type of paper being used which wouldn't cause problems with condensation later.
 
Birroc, I have been advised by the screed company to make sure the pipes are well secured with galvaband otherwise they will rise to the top of the screed. (That is if you are using the liquid screed) Taping the joints is not enough and you need to use minimum 500 guage polythene to prevent reaction with the foil and to prevent the Kingspan from "floating" if the concrete gets between the joints. Cold bridging will be prevented also.
 
rmdt said:
You should also use perimeter strips at the edges where the slab meets external walls (some people recommend the same for internal walls, depending how serious you are about the job). These strips are about 6 inches high and 1 inch thick.
Click to expand...

Thanks for all the prompt replies. 500 gauge polythene - good to know.

rmdt, what are the perimeter strips made from ? Do Kingspan do them ?

Jorus, what do you mean by "going to scrape and clean the floor first" -how will you scrape a concrete raft floor ?
 
Birroc said:
Thanks for all the prompt replies. 500 gauge polythene - good to know.

rmdt, what are the perimeter strips made from ? Do Kingspan do them ?

Jorus, what do you mean by "going to scrape and clean the floor first" -how will you scrape a concrete raft floor ?
Click to expand...


birroc.. are you going to slab the internal of the external walls with insulated plasterboard?
 
sydthebeat said:
birroc.. are you going to slab the internal of the external walls with insulated plasterboard?
Click to expand...

No Syd, external walls already plastered. No insulated plasterboard at all, never liked the idea. Went instead for 150mm cavity full fill of ecobeads.
Why do you ask ?
 
Birroc said:
No Syd, external walls already plastered. No insulated plasterboard at all, never liked the idea. Went instead for 150mm cavity full fill of ecobeads.
Why do you ask ?
Click to expand...


because if you were its adviseable to put wider perimeter strip insulations around the floor to touch the insulation on the insulation backed plasterboard, it forms a much better thermal barrier.


anyway, your not so...

i would incorporate at least a 25mm strip around all the external (and internal!!) rising walls.

on the 500 gauge ploythene 'slipping sheet'... this is definitely a good idea.... but if budget allows id try to use a 1200 gauge.

if you want to do a better job, but with a bit extra work... lay two sheets of 50mm instead of one sheet of 100mm.... when doing this stagger and tape the joints.... 100mm boards can tend to buckle and rise...
 
birroc:

[broken link removed]

look at this little vid....

pay attention to the strip insulation thats installed just as the floor board insulation drops into place...

its located at the external walls to create a thermal barrier between the block and the concrete floor.

also....
look at page 4 of this document: http://www.environ.ie/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad,18751,en.pdf

you can see the strip insulation at the wall...

let these details be your bible!!!
 
Thanks Syd, I think I understand it now.

Would 30mm of Kingspan floor insulation be enough to use as a strip ?

I notice in the video that the floor insulation rests against the strip insulation (which stands on the concrete raft) but in the document the strip sits on top of the floor insulation (which touches the block wall direct).

Which would you recommend ?
 
i recommend the strips sit on the board...

your cavity insulation should start 225mm below finished floor level as well.
 
I used the xtratherm strips that Sydthebeat mentions. They are 25mm X 150mm X 1400mm and are really handy. It saves cutting strips from full board and have foil on both sides. I put in 75mm xtratherm and will be putting in 75mm screed once the plumber finishes the pipework.
 
Birroc,

On the point of starting your cavity wall insulation 225 below FFL.If you are going to do this make sure that you fix this to the inside leaf.Your wall ties will only start at FFL so if you don't fix the insulation below this it will be loose and may lie across the cavity.Any mortar droppings can build up and allow water to seep across your cavity.

Personally I would not put the insulation below FFL for this reason as you will inevitably have a certain amount of mortar dropping and this provides a space for it to accumulate without causing any harm - once it doesnt build up above FFL.
 
builder ed said:
I used the xtratherm strips that Sydthebeat mentions. They are 25mm X 150mm X 1400mm and are really handy. It saves cutting strips from full board and have foil on both sides. I put in 75mm xtratherm and will be putting in 75mm screed once the plumber finishes the pipework.
Click to expand...

Oh ok, so these strips are a seperate product. I was going to cut the Kingspan boards to make them.

Is this xtratherm better than the Kingspan equivalent ?

A friend told me that aeroboard would be just as effective given that I am pouring concrete screed on top of it. What do ye think ?
 
Kingspan and xtratherm are both pretty much the same stuff. However aeroboard isn't. There is no problem using aeroboard, but you will need to use a greater thickness of it to give the same u value.
 
wexford dude said:
Birroc,

On the point of starting your cavity wall insulation 225 below FFL.If you are going to do this make sure that you fix this to the inside leaf.Your wall ties will only start at FFL so if you don't fix the insulation below this it will be loose and may lie across the cavity.Any mortar droppings can build up and allow water to seep across your cavity.

Personally I would not put the insulation below FFL for this reason as you will inevitably have a certain amount of mortar dropping and this provides a space for it to accumulate without causing any harm - once it doesnt build up above FFL.
Click to expand...
Would you not just build in a set of wallties one block down for FFL.............
 
wexford dude said:
Birroc,

On the point of starting your cavity wall insulation 225 below FFL.If you are going to do this make sure that you fix this to the inside leaf.Your wall ties will only start at FFL so if you don't fix the insulation below this it will be loose and may lie across the cavity.Any mortar droppings can build up and allow water to seep across your cavity.

Personally I would not put the insulation below FFL for this reason as you will inevitably have a certain amount of mortar dropping and this provides a space for it to accumulate without causing any harm - once it doesnt build up above FFL.
Click to expand...


you NEED to do this now to comply with building regulations.

Its easy to do.... just put in small pieces of insulation in the cavity to hold it in palce.

Its bad practise to allow mortar to fall into the cavity.
 
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