Avoiding damaging that precious DPM

[wavetrain]

An interesting set of pics from a self builder here: http://www.tony.warner.btinternet.co.uk/photo.htm

A question for those more expereinced than myself, take a look at this set: http://www.tony.warner.btinternet.co.uk/Phase1c.htm

He/she have laid the concrete to below DPC and I guess may screed it to DPC later.

I have noticed on other's projects, the DPM can get ripped a bit after the concrete is laid if it is still visible and I would not want that to occur on my projects

Another detail I have seen drawn is lay the concrete to DPC then lay screed to a level above DPC.

What do others consider best practice to minimise the risk of puncturing the DPM after concrete has been placed?

 

[noseall]

At the external wall abutments there will be an up-stand of insulation protecting the dpc.

Otherwise, nay bother.

 

[wavetrain]

At the external wall abutments there will be an up-stand of insulation protecting the dpc.

Otherwise, nay bother.

dpc? I was writing about the DPM, as for the rest, I don't think so.

 

[noseall]

At the external wall abutments there will be an up-stand of insulation protecting the dpc.

Otherwise, nay bother.

dpc? I was writing about the DPM, as for the rest, I don't think so.

Sorry a typo i meant to scrawl dpm.

What do you mean by "i don't think so"?

 

[wavetrain]

Well I am bothered about a damaged DPM, I'm sorry if you are not.

And I raised a topic which relates to generic global DPM use, not just to current BC rules in the UK.

 

[stuart45]

The most common causes on site of DPM damage are
1. Labourers putting holes in it with the fork to let out rainwater.
2. Damaged by the tamp.
3. Bricklayers trimming it to size with the brick trowel.
For number 2 BRE recommend (in one of their Good Building Guides) fixing a batten to the brickwork and cutting a tamp to go over the top and to to level of the concrete. Has anyone ever seen this done on site?

 

[freddiemercurystwin]

Well I am bothered about a damaged DPM, I'm sorry if you are not.

And I raised a topic which relates to generic global DPM use, not just to current BC rules in the UK.

wavetrain you need to lighten up a little.

Its quite possible to take the dpm and the slab all the way through the wall (so that the edge of the slab lines up with outer face of the inner skin and lap it up the outer face of the slab and tuck it under the dpc in the wall infact this is becoming the norm in Devon to ensure Radon protection is not compromised. It is more work for the builder as there's nothing to cast the slab up against. This way the edge of the slab is supported on the inner skin and cannot drop whereby should a purely ground supported slab drop a little as the ground settles beneath it, it'll likely tear the dpm where its exposed if conventionally detailed.
This method still leaves the dpm exposed though. If its a large building it could be exposed for months before its protected by the rest of the building fabric.

When all's said and done though its a sad fact of the industry that there are loads of things site operatives do that they shouldn't.

 

[wavetrain]

Thank you for that info FMT, but without diagrams as a guide I am not at all clear on your text I'm afraid. But what I do know is I would wish to choose a design that eliminates the possibilty of the slab settling on my single leaf outbuilding project.

The reference I have to go by which has diagrams I can follow is this book which I have a copy of:

BCHcover

• wavetrain
• 29 Apr 2009
• 1

Hopefully this subject will become clearer in due course before I need to decide on the groundwork design.

 

[freddiemercurystwin]

Untitled

• freddiemercurystwin
• 29 Apr 2009
• 2

Not to scale obviously but gives you the idea and as mentioned it still leaves the dpm temporarily vulnerable, the slab won't drop though.

 

[Shytalkz]

SU and parallel projection, no?

You forgot to mention the need for mesh/rebar in the bottom, FMT, if the slab is going to be suspended.

I'm not sure why Wave is so paranoid about his dpm: does he have a radon/gas problem???

He could avoid a poly one altogether and use a painted one on the slab topside, of course.

 

[wavetrain]

TY for that FMT, I used to be like you with those demo mode marked PDF writers until I found http://www.pdf995.com/

which has a 10 second nag screen but no watermark, it changed my life!

I am not paranoid about DPMs but I do worry about damp and I am not happy with having damp structures above floor level lurking behind a ripped piece of plastic. ALthough some people seem to be able to live happily in a damp smelling building, not I, as I can detect damp with ease - the nose knows - and I take the view of Corporal Jones with rising damp, "they don't like it up um!"

I will post some drawings in a day or so to illistrate this, and also of my possible design.

BTW I am not keen on insualtion under the DPM, what's that all about?

 

[freddiemercurystwin]

BTW I am not keen on insualtion under the DPM, what's that all about?

Oh FFS stick it where you like! I knocked up a detail in my spare time which stated:

but it gives you the idea

and I downloaded some crappy demo software to my home laptop to create a PDF and downloaded some more crappy software to convert it to a jpg because I wanted to help another forumite.

If you bother to search the World Wide Web you’ll find dozens of variable ways of doing this detail.

I am not paranoid about DPMs but I do worry about damp and I am not happy with having damp structures above floor level lurking behind a ripped piece of plastic. ALthough some people seem to be able to live happily in a damp smelling building

You F***ing well are and who’s happy to live in a damp smelling building?

You should be more worried about

When all's said and done though its a sad fact of the industry that there are loads of things site operatives do that they shouldn't.

 

[wavetrain]

FMT calm down! This forum allows light hearted banter does it not?

Just for info, I am a self builder and therfore I determine the quality of the work done.

 

[Shytalkz]

Oh FFS stick it where you like!

 

[hotrod]

Oh FFS stick it where you like!

I would be careful who you say that to if I were you. Forum members of a certain persuasion may assume, given your username, that's 'a ticket to ride'