Flooring over polystyrene

[bigegg]

Im building a conservatory.
I have a 4" concrete subfloor over 4"hardcore.
I laid a dpm, then 3x1" layers of expanded polystyrene over as a insulating layer.

Im looking for advice as to how to finish off.
Can i pour a 2" slab straight over the top?
Would i be better with 2" of insulation and a 3" slab?
Can i use a sand/cement render (2") rather than concrete? (im thinking not)
Chicken wire reinforcing? (fastened to xps? Midway? Both?)
Should i glue the layers of xps together first?
Another damp proof over xps?
Other issues: im using 2nd hand xps, so there are some small voids.
Ifilled the larger with patches, and sealed over joints with duct tape.

Would i be better off putting a layer of osb down, and a lino/laminate floor rather than 2" of concrete.
i miscalculated floor height by one brick height - i was intending a 4" slab + tiles.
Needs to be level disabled access, so i have no option for thicker slab

 

[julianf]

Im sure that, when my olds had theirs done, it was board over the insulation, and then tiled.

(i never understand how tiles work on board, but its common, so they must)

 

[bigegg]

Additional info: i say conservatory, but in reality, its going to be a 3m x 3m greenhouse/ wet weather laundry drying room.

 

[Hitch]

I'd have said a 50mm sand/cement floating screed would be a touch on the thin side...?
Would it be worth the extra dosh swapping the XPS for Cellotex, so you can have a thicker screed?
If you have to go thin, i'd think its worth using pp fibres and some 2x2 mesh to minimise the shrinking/curling...?

Obviously not my day job, so someone else might have a more suitable plan...

 

[rikrobson]

I would have thought board over the insulation (18mm ply) then tile over that.
the board spreads the point loads over the insulation sheet and the tiles waterproof it all.

how mutch do you neet to make up from the top of the slab to the required floor level?

 

[colnerov]

Hi, With that amount of glass do you require so much insulation under the floor? Could you reduce the insulation and increase the thickness of the overslab? Again not my day job so what do I know.

Colin

 

[bigegg]

I have about 5" in total from underslab to required floor level.
+- 1/2"

Another alternative could be reduce insulation to 2", then a 1" layer of dry sand/cement, then 2" paving slabs?

 

[bigegg]

Hi, With that amount of glass do you require so much insulation under the floor? Could you reduce the insulation and increase the thickness of the overslab? Again not my day job so what do I know.

Colin

At the moment, this is my preferred alternative.
One of my issues is that the individual layers of xps are not as stable as one single layer.
Theres no budget for different insulation - its this or nothing.
So i either find a way of stabilising the layers, or remove them.

 

[mpats]

If you do tile over board a tiler I know always advises going for 22mm ply as he sees better results with it, no cracking etc. That may just be compared to normal flooring hardboard though.

 

[gaz1]

4" is the preferred thickness for foot traffic 3" at a push but not any thinner

as 5" isnt enough to install the proper insulation can you go deeper at all?

if not and 2" isnt think enough then id be looking at a water heat system but you will lose heat through the ground you have to decide if its norminal to use this system but more so if you can get a free type of heat system running for it an underheating system pex pipe should be good enough

 

[Gritineye]

Flooring grade 22mm chipboard with glued tongues, 3/8" gap all round, skirting board to cover gap. If there's danger of water spillage, paintable seal the bottom of skirting to floor .

Polythene under chipboard to stop polystyrene squeaking important

Easy and clean, warm and dry, done loads like it.

 

[mike os]

I take it this is not being inspected?

50mm sand n cement screed is more than adequate in most situations but needs to be fully supported. . Ie no gaps in any of the insulation

 

[rikrobson]

looks like im a cheapskate then only saying 18mm ply

 

[bigegg]

I take it this is not being inspected?

 

[mpats]

looks like im a cheapskate then only saying 18mm ply

Doubt you're cheaper than an Aberdonian

 

[addjunkie]

When we did our house its a sub floor dpm concrete, 4 inch thick, 100 mil kingspan, underfloor heating pipes, thin 2nd layerpolythene, expansion foam around the edges too, then 75 mil of liquid screed was pumped in

 

[Wendelspanswick]

Our kitchen extension floor was, from top to bottom,
12mm porcelain tiles
Tile adhesive with underfloor heating mat laid in.
50mm sand/cement screed.
150mm polystyrene*
DPM
10mm sharp sand
Block and beam floor.

Passed inspection by the local authority.
It's been down about 10 years, gets lots of traffic and looks as good as the day it was laid.

*I would have used 100mm of polyurethane foam but I needed to make up the extra 50mm to match floor levels.

 

[gerrymoore]

I built my own conservatory about 4 years ago. I used 2" of XPS over the DPC and about 3" of concrete at 4:2:1. I tiled over this with Brazilian slate and it has been fine.

1st pic laying floor in 2012...second pic today...

 

[Gritineye]

Even when DIYing one has to keep in mind materials spend and labour time over fuel savings, it soon becomes a matter of diminishing returns, it's only a conservatory and unless it's vast it can sometimes get a bit sledgehammer and nut.

 

[DrDeAtH]

Vapour barrier over the insulation (plastic dust sheet is ideal), then screed as normal. You can throw some fibres into the screed mix if you want to, but shouldn't be necessary. 4:1 mix sharp sand to cement. not too wet.