Can someone in the building game...

[rodgy-dodge]

( some of you will know we are doing a self build extension)... could someone explain what we do with the dpc that sits over the patio door opening? Do we mortar this in? I can't find any information on what to do with it. Even building regs are vague. We have the cavity closers for the sides, but the brickies have just left the dpc over the door opening loose. do we just trap it between the upvc sill. My instinct would be to adhere it with mortar. Can anyone advise

 

[Dewi]

I think you mean at ground level rather than a cavity tray DPC over the lintel? Traditionally all frames would be built in as work progressed and bedded in mortar, these days it's a bit more vague, as you've found. In most cases the DPC is left loose then fixed in place once the sill is fitted and any gaps sealed with expanding foam. DPC won't stay in place if just bedded with mortar, it needs some weight on it unless you tied sticking it down with mastic or bitumen paint. So long as the DPC is there and there are no unsealed gaps for rain to penerate it doesn't really matter.

 

[rodgy-dodge]

Thanks Dewi yes thats what I meant, the bottom of the door (threshold), most of the information I've found only refers to wooden doors and sills knothing about upvc! the door company asked if it was a new build and said we needed a sill, (i've got so much going on in my head I know, I should have asked there and then if it sat on top of the dpc and how it would be secured? me being a woman they look at me as though I'm an alien! I just want ot make sure we get it right first time...

 

[asterix]

Stick a bit of frame sealant on it, right round, no gaps.

 

[rodgy-dodge]

Stick a bit of frame sealant on it, right round, no gaps.

We are on about just the dpc?

 

[asterix]

I assumed that the DPC is at the level you want and you can rest the frame straight onto it. In fact you don't need a DPC to protect the UPVC frame because unlike a timber frame they are impervious to damp. However if you have timber floors you won't want damp coming under the frame causing decay to the timber. Hence the sealant.

If your DPC is low you will need to get the right level with screed on top of the DPC. Then put the door frame onto the sealant on the screed.

 

[dellzeqq]

honestly, RD, it's a three dimensional thing and if you get people to give you an answer in words (despite Asterix's bold attempt) you will be in trouble. The general principle is
- connect bits of dpc and dpm (damp proof membrane) in accordance with the manufacturer's instructions - and if those aren't clear, write to them
- and, by doing so, separate wet stuff from dry stuff, always allowing moisture to migrate from wet stuff

 

[Archie_tect]

I'm nervous about giving advice without seeing the detail, but the vertical dpcs in a conventional masonry cavity wall in the jambs [the sides] separate the outer leaf from the inner leaf... then at the bottom of the door opening those vertical jamb dpcs need to dress over the outside face of the cill dpc which is dressed in an L shape facing outwards under the cill below the frame to protect the inner leaf blockwork or timber frame. There should be a 150mm vertical upstand to the long dpc under the cill so that any moisture or driving rain drains down the outside of the cill dpc upstand and then out through the wall. You should have stop ends on the sides which should extend just beyond the vertical dpcs to the jamb ends and weepholes in the vertical joints of the bricks/stone on the outer leaf to let any water out of the cavity- that stops any moisture or water that can into the cavity due to driving rain dripping off the ends and that is best practice construction. DPCs should always form a continuous barrier around the frame to separate the outer leaf [damp side] from the internal [dry side] without relying on mastic or sealant. In fact I wouldn't recommend using expanding foam filler unless you are sure the cavity is fully closed around the masonry door opening as it can block the cavity and allow water to drain onto the inside leaf... there should be an effective drip overhang to the door frame to stop water being blown by the wind back onto the wall underneath.

Sorry if this is stating the obvious.
[Edit: Dell's more concise answer has beaten me to it while typing!]

 

[asterix]

So that's 2 for mastic and 2 not really sure?

 

[dellzeqq]

you can put me down as being entirely against mastic

 

[threebikesmcginty]

So that's 2 for mastic and 2 not really sure?

The 2 that are for it are bodgers and the two not really sure will tell you what is best but only for £150/hour.

 

[asterix]

Well I look forward to hearing how the OP solved the problem, anyway.

 

[Archie_tect]

Experience tells you never to be really sure!

 

[rodgy-dodge]

I'm nervous about giving advice without seeing the detail, but the vertical dpcs in a conventional masonry cavity wall in the jambs [the sides] separate the outer leaf from the inner leaf... then at the bottom of the door opening those vertical jamb dpcs need to dress over the outside face of the cill dpc which is dressed in an L shape facing outwards under the cill below the frame to protect the inner leaf blockwork or timber frame. There should be a 150mm vertical upstand to the long dpc under the cill so that any moisture or driving rain drains down the outside of the cill dpc upstand and then out through the wall. You should have stop ends on the sides which should extend just beyond the vertical dpcs to the jamb ends and weepholes in the vertical joints of the bricks/stone on the outer leaf to let any water out of the cavity- that stops any moisture or water that can into the cavity due to driving rain dripping off the ends and that is best practice construction. DPCs should always form a continuous barrier around the frame to separate the outer leaf [damp side] from the internal [dry side] without relying on mastic or sealant. In fact I wouldn't recommend using expanding foam filler unless you are sure the cavity is fully closed around the masonry door opening as it can block the cavity and allow water to drain onto the inside leaf... there should be an effective drip overhang to the door frame to stop water being blown by the wind back onto the wall underneath.

Sorry if this is stating the obvious.
[Edit: Dell's more concise answer has beaten me to it while typing!]

honestly, RD, it's a three dimensional thing and if you get people to give you an answer in words (despite Asterix's bold attempt) you will be in trouble. The general principle is
- connect bits of dpc and dpm (damp proof membrane) in accordance with the manufacturer's instructions - and if those aren't clear, write to them
- and, by doing so, separate wet stuff from dry stuff, always allowing moisture to migrate from wet stuff

Thanks Guys these pieces of advice are great to be going on with. Can I just say I hate Mastic too. Its ok in some situations, but I would always look at alternatives first! Everything is in place as said by Archie. My main concern was the loose DPC at the threshold of the door, The concrete floor has gone in this morning so the inner (thermablock wall) DPC is held in place as the floor membrane goes up under that DPC thus holding that side in place. I can visualise how its going to work now so thanks again guys...If your interested in the build I'm blogging it on my blog site 'Project 2012'