Screed depth? ?

[jimmya78]

I have to screed a floor in my extension, its 6.2x 3.4 its going over celotex. The trouble is I only have a maximum depth of 50mm for the screed. Does anyone think thats ok or should it be deeper?? Thanks guys

 

[johniosaif]

Bit thin, maybe sbr and fibres , or liquid screed. ,

 

[malc]

why dont you put down thinner celotex so that you can get 3 inches of screed. what finish is the screed to receive ?

 

[jimmya78]

Evening Malc, its only cos I over ordered celotex when I did the roof and the builder put down to much concrete when doing the dub base. I have 8 sheets of 100 mm which pushes level up! Its probably gonna be a tiled finish

 

[johniosaif]

Best to get 75mm insulation ,that would leave it almost adequate ,I would put sbr and fibres in the screed also

 

[jimmya78]

Thanks johniosaif. Not being funny but do you think I could shave the back off the 100mm boards I have to make them 75mm??

 

[beddy]

Can you not swap it for 75mm

 

[jimmya78]

No beddy had them for months!

 

[flynnyman]

Thought 50mm is minimum for floating floor so you should be ok but I'm not 100% sure just something in my head

 

[PFTwales]

min 75mm with fibres on a floating floor. liquid screed is minimum 35mm

 

[flynnyman]

If you go for a flows reed I think it's even thinner so this might be an option

 

[PFTwales]

Whats a flow screed. is that liquid screed finny. Weber have a screed that can go 25mm over insulation ££££££££££££££££

 

[johniosaif]

65mm I think is the min on insulation for normal.very hard to cut them down to 75 mm jimmy, seven sheets, I have seen it tried before...

 

[carlos]

Does liquid screed have to be pumped? Or can you just mix it with a paddle and tip the buckets in?

If say you only have a little floor to do.

 

[superspread]

You could also lay chicken wire in the screed or is that old hat now:RpS_confused:,I use to do it that way

 

[malc]

as the finish is going to be tiled i would lay a 2" screed. it is a good idea to reinforce the screed with chicken wire, just place a layer of screed on the cellotex then lay the chicken wire, so that the chicken wire is in the middle of the screed, not laying on the bottom.

 

[johniosaif]

You could also lay chicken wire in the screed or is that old hat now:RpS_confused:,I use to do it that way

Not recommended anymore ,fibres instead

 

[superspread]

Not recommended anymore ,fibres instead

Both ?

 

[malc]

i use fibres when i am asked to but i do not think that they do a good job, as now they are to short at about 20mm. i felt that they where ok when they where about 75mm.
when they go through the ready mixed screed lorry they are just throw a packet in now and again and they do not go through the mix constant.
that is why i would use chicken wire on this screed.

 

[bodders13]

They should be consistant at 900grams per cube. The length is irrelevant due to the shear number off fibres per cube being greater now that they are shorter.

 

[kebab king]

I add my own fibres and mix it in the mixur, normally with SBR.

 

[essexandy]

@jimmya78 if you've had 100mm insulation spec'ed on the plans then don't even consider putting down less, building inspectors will often want to check what has been laid. Personally if it was on my own place I'd just lay the screed with fibres, making sure it's a proper strength screed, most peoples screeds are weak. If it was for a paying customer I'd suggest putting A142 mesh into the screed, possible overkill but it make both client and building inspector happy.
As an aside, quite a lot of jobs we're pricing now have 150mm insulation spec'ed. Now that is a pain in the balls.

 

[jimmya78]

Thanks @essexandy

 

[flynnyman]

Whats a flow screed. is that liquid screed finny. Weber have a screed that can go 25mm over insulation ££££££££££££££££

Yes

 

[JPS]

Jimmy I would use weber floor 4310 it is a fibre reinforced self levelling screed and can be laid between 25-50mm on insulation. Just add 5 later water and mix with a paddle and pour on to floor . If your not too worried about the appearance of the screed then leave it at that otherwise just light tamp the top and you will get a nice finish.