quick question for tilers

[paul1966]

I am currently digging out an old concrete floor to lay a new slab and then i want some 1 inch quarry tiles laying, the slab will be 150 mm thick so allowing 25 mm for the tile and 10 mm for adhesive. Is it as simple as adding all that up so i dig out to about  185 mm below the top of the existing tiles that will be tiled up to?

[Scully]

Makes sense to me, if you want your new floor to finish where the existing one is? 

[millrace]

7 minutes ago, Scully said:

 

 

No not really!!

(Cant remove the quote box)

 

 

 

 

 

Edited October 18, 2021 by millrace

[Scully]

1 minute ago, millrace said:

 

No not really!!

 

 

 

 

 

Ah well. Not to worry. 🙂

[millrace]

Sorry scully wasnt even trying to quote you...

To answer floor make up is as follows

Take out existing 

If no hardcore you need prob 100mm compacted

Then 100/150 subfloor concrete then damproof membrane then 50/100mm of polyiso insulation  then say 75/100  cement screed 

Now your tile buildup of 35/40mm

So basically your looking at removing 400 mm + below existing floor height!!

Or of coarse you can just fire in bit of concrete tile over and then scratch your head as to why you have damp/ cold bridge problems a year down the line!!

Edited October 18, 2021 by millrace

[paul1966]

Ok thanks there is hardcore down already, won't know how deep it is until i gig down a bit. The DPM I knew about, the insulation, is it worth having as the existing floor hasn't got any and the new slab is only 3m x 2.5? 

[39TDS]

1 minute ago, paul1966 said:

Ok thanks there is hardcore down already, won't know how deep it is until i gig down a bit. The DPM I knew about, the insulation, is it worth having as the existing floor hasn't got any and the new slab is only 3m x 2.5? 

Yes it is worth it and I would expect building regs insist anyway. I'd be doing 150mm insulation

[Jaymo]

14 minutes ago, 39TDS said:

Yes it is worth it and I would expect building regs insist anyway. I'd be doing 150mm insulation

Building regs for new builds and extensions to existing buildings. 
 

150mm- of what grade/manufacturer as ‘r’ value is diff for all.

You can have same value for half the depth. 

[paul1966]

is it possible to lay the floor as- hardcore, sand, DPM, insulation, concrete slab, doing this way would be easier for me as i can get the concrete done in one go.

[millrace]

You "can" do what ever you want.....!!....lol

 

Years ago we used to kinda of do it that way but always put a screed on top....

So...  hardcore /insulation /subfloor dpm/ screed

Resulting in poor uvalves and potential cold bridge...

But heres the thing....if your in an old poorly insulated building doing this small floor to new regs aint going to make any odds to the house!!

[Scully]

1 hour ago, millrace said:

Sorry scully wasnt even trying to quote you...

To answer floor make up is as follows

Take out existing 

If no hardcore you need prob 100mm compacted

Then 100/150 subfloor concrete then damproof membrane then 50/100mm of polyiso insulation  then say 75/100  cement screed 

Now your tile buildup of 35/40mm

So basically your looking at removing 400 mm + below existing floor height!!

Or of coarse you can just fire in bit of concrete tile over and then scratch your head as to why you have damp/ cold bridge problems a year down the line!!

Nee worries! 🙂

[paul1966]

1 hour ago, millrace said:

But heres the thing....if your in an old poorly insulated building doing this small floor to new regs aint going to make any odds to the house!!

And there i think you have hit the nail on the head. If i were living in a new build no problem but a 1950's house that is draughty anyway why bother? We have dug out down to about 400mm and a majority of the hardcore was broken up clay pipes, no doubt thats what is under the existing kitchen floor, whether there is a DPM under it who knows, what i do know its not sank and there is no damp.