Stud Walls in New Extension - When to Build Them!?

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Hi,

I've just joined having recently had a two story extension completed, the builder has done pretty much everything I asked him to do so now I have a large empty space with a nice new 100mm concrete subfloor.

On top of this the plans show 1200 Visqueen then 75mm Celotex then 500 Visqueen then 75mm screed which seems to make sense.... ish!

In the extension I need to build two internal stud walls to break the space up into a hallway and a utility room. I'm happy enough to do this but I need to know when I can do it..... I would like to do it before the Celotex and the screed so the electrician etc. can get going but if I do then surely I will puncture the Visqueen when I fix the floor plate to the concrete floor and I assume this isn't good? On the other hand should I fix the wall to the finished screed bearing in mind this is on top of Celotex?

Any advice would be much appreciated!

Thanks,

Paul
 
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The wall goes on top of the screed, this avoids creating a thermal bridge, and allows for fixing with no problems and no broken DPM
 
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Thanks ^woody^ appreciate the info. Doing it after the screed sounds logical but..... are there any options for doing it sooner? Reason being the screed isn't going to get done for some time yet as the plumbing, electrics etc. etc. all need to be done first.

The kitchen can't be ordered until internal walls are built and the space measured so it's a bit of the old domino principle..... I was told that laying a couple of courses of bricks onto the Visqueen then building the stud walls onto that could be an option?

If building them after the screed is the best option then I can go with that but if there are equally viable options that could speed things up I would like to explore those too.
 
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Its a poor design if the DPM is above the concrete

Anyway, lay a 1m wide strip of DPM where the wall will be, and this will be lapped to the main DPM later. Then lay brickwork on this to the level of the finished floor. Then fix your sole plate to this.

Fold the DPM up so that it does not get damaged until you come to lay the rest of the DPM. Then join the DPM's with two or three 100mm folds and then tape the join with duct tape or proper DPM tape
 
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Thanks for the information all, much appreciated.

Re: Why a concrete floor and not a timber frame - there is underfloor heating going into the extension so I was under the impression that this would mean the floor should be the 100mm of concrete then 75mm insultation then a 75mm screed and the underfloor heating pipes will be under the screed. This is also how it is shown on th plans.

Re: Why not block walls - again tis is as it is on the plans but I was also led to believe that timber walls would be the better option as these could be insulated? I have a couple of pallets of blocks left over so if they would be blockwork then that would make good use of them and save having to buy timber, I couldn't do that myself though..... Also if this was an option am I right in assuming it would be the same principle as ^woodys^ solution i.e. build the wall on a 1m strip of DPM then join it to the DPM for the remaining floor space?
 
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