Preparing to Screed - What to consider....

[Mulberry View]

I have a Beam & Block floor and am hoping to screed soon. I have 230mm of insulation going in, it's all here on site. The Beam & Block is grouted and fully dry. The grout has "cracked" in places, but just superficially. There are gaps in places at the perimeter to the subfloor. Should these be sealed?

 

I have 4 soil pipes and a blue 110mm water pipe duct coming up through the floor blocks. Do these need to be specially sealed in any way at Beam & Block level? The soil pipes are plain ended and currently plenty long enough, should I solvent weld socket couplers in the insulation level to remove the joint that faces the wrong way or just live with the plain pipe ends and worry about connections later above the floor level?

 

Do I need to consider air-tightness in the way to DPM is installed and terminated onto the Nudura walls? PIR upstand yes or no?

 

The screed is likely to be Cemfloor at a thickness of 50-55mm, containing UFH (yet to be installed of course).

 

Any tips or words of advice to limit my inevitable procrastination would be massively appreciated.

[Russell griffiths]

Get some neoprene insulation material 100mm wide, wrap this around the soil pipes at screed level. 
2 wraps around will leave you with a void around the pipe so when the screed is in and dry you will either have a bit of wiggle room on the pipe, or you have the ability to pull the neoprene out which leaves a void that a pipe coupling will fit into. 
as for sealing them you will be putting your dpm on top of the beam n block so you seal the pipes to that. 

[JohnMo]

I made insulation corners a bit bigger than the tape lines to enable lots to wriggle room. Once screed had cured, broke out the insulation. Did what I needed when bathroom etc was being done, then back filled with cement mix.

[Nickfromwales]

I just use a few ‘turns’ of squirty foam to give said wiggle room, but as above, more importantly, gives you the option to slide a fitting (with its knuckle) after removing some of the foam. 
 

 

I am in the process of fine tuning the 1st fix for the GF cloak WC that this particular pipe services. There’s a full 20mm of ‘wiggle’ there, allowing me to get the fully-back-to-wall close coupled WC in to perfection. Cost, £5. 

[Nickfromwales]

12 hours ago, Mulberry View said:

The soil pipes are plain ended and currently plenty long enough, should I solvent weld socket couplers in the insulation level to remove the joint that faces the wrong way

Nope. And there isn’t a ‘wrong way’ here btw .

 

Most UG pipe is sold ‘socket-less’ meaning it is just straight pipe (plain ended as you call it) which is directionless and completely normal.

 

FYI a ‘socket’ is what the plain pipe goes into for each joint, so you get single or double ‘socket’ bends, one male and one female end, or both ends female.

 

We’ll learn you good, boy!!  

[Nickfromwales]

12 hours ago, Mulberry View said:

Do I need to consider air-tightness in the way to DPM is installed and terminated onto the Nudura walls? PIR upstand yes or no?

I chatted this through with one previous client in Gravenhill, as they only allow a B&B floor there. We decided it best to buy a few (very) large tubs of black jack (liquid DPM) and use that to make the B&B airtight too; this was brushed up the upstands too. 
 

Here’s a pic of it, please ignore it being wrecked temporarily to install the WC pipe where it actually needed to be, lol. Back in the trenches again   

 

 

This was done vs a sheet DPM, and imho this is night & day better. Zero tape / dodgy internal and external corners to fold. 👍👍👌

 

Oh, and yes, I did have to suspend that WC frame in place, FFL calculated and datums a plenty, stud wall created virtually in mid air, before the polished concrete went down…….

 

I had about 4mm of tolerance to play with.

 

All was A1 of course as OCD wins every time lol.