DPC not lapped as specified by architect

[Tim1985]

The DPC has not been lapped as specified by the architect.  A 100m DPC was used instead for the inner leaf of the cavity. 

 

Is this ok and what can be done to make sure that there are no damps .  Can it still be lapped with the DPM any other way

[Temp]

The DPM under the floor slab should really go up the wall and lap over onto the DPC. I can't guarantee it will be OK but I suspect as long as it's lapped up the wall to a point a few inches above the DPC it will be OK. 

[Mike]

No, it's not OK.

 

I'd apply a couple of coats of liquid DPM for (Aquaseal Hyprufe of similar) for 100mm or so above the slab, thoroughly sealing along the DPC, and along the edge of the slab itself, so that the DPM laps with that. Make sure the joints between blocks are pointed first if they're not already 100% full.

 

This is something to discuss with your Building Control Officer as it's a stage they should be checking.

[johnhenstock83]

you'd normally leave some DPC overlap inside, around 1ft, to be able to connect it to your damp proof barrier. having said that, I'd agree with @Temp, it's not the end of the world. what you're basically doing with the DPM is to create a "tray" or a "bag" that seals your floor from touching anything wet/damp. since it goes above the DPC, the wall directly opposite the screed should not be wet anyway, so I guess you'll be ok.

[Dave Jones]

the cavity under the door looks to be filled with conc, it needs some insulation in there to stop thermal bridging and damp.

 

[Canski]

3 hours ago, Dave Jones said:

the cavity under the door looks to be filled with conc, it needs some insulation in there to stop thermal bridging and damp.

 

It amazes me how often we see this.

[saveasteading]

These appear to be engineering bricks, so won't absorb much water.

So in reality it will probably be OK, but it should not have occurred. 

The suggestions above are good.

It is essential that the bco sees this before it goes further.

[LiamJones]

I’ve had exactly this just happen, was expecting 450mm dpc to be used on inner leaf, it’s sitting there on site. Arrived tonight to find 100mm dpc has been used on both leaves 😫when is that ever the right thing to do? 

[Canski]

On 04/10/2023 at 19:22, LiamJones said:

I’ve had exactly this just happen, was expecting 450mm dpc to be used on inner leaf, it’s sitting there on site. Arrived tonight to find 100mm dpc has been used on both leaves 😫when is that ever the right thing to do? 

I feel your pain. OK sorry guys but it’s rant time. I need to get this off my chest after a few Madris. Tomorrow is my first ‘day off’ for 3 months due to my Chippy being delayed for a day. and I’m heading to grand designs at the NEC. My thoughts on your post ….You can never take your eye off the ball. I’m a brickwork contractor and running out of bricks with the amount of work I’ve had to have taken down on my own project.  Nobody gives a fu#@ any more. You can lead a horse to water but you can not make it drink. I show them how to do it set everything up for them then turn my back for half an hour and it’s screwed up. My best guys who have been with me for 25 years + are stuck on another project that pays my bills  so I end up with the B team. Plot 2 is my house and plot 1 is my friends. I tested the guys out on mine then got fed up with poor workmanship and lack of listening so sent them elsewhere. To be fair I have employed a lot worse than them but we soon part company.  My plot took 312  man hours to get to joist then I did most of plot 1 and completed it in a total of 230 hrs. I’m not blowing my own trumpet  (much) but  the quality is far better. Hard graft, long days 6 days a week on site and one in the office but I have loved every minute. Aside from my A team I am completely fed up with employing people. Next time I am doing one house and I don’t care how long it takes I am doing the brickwork myself or with the A team. How can people do this job for 20 years plus and still be shite ? It’s easier and quicker to do it right the first time. 

[Brickie]

I hear you @Canski -I don’t currently employ anyone (&have only ever had max two on for me) but the lack of engagement with the task in hand is par for the course. Got a lovely fella working with me (not for me) but Jeez-can’t lay to the line,puts ties in the wrong course,forgets tray damp,overall has no concept of problem solving. Just have to keep telling myself ‘he doesn’t work for me,he doesn’t work for me.’ 
 

[saveasteading]

8 hours ago, Canski said:

got fed up with poor workmanship

Wherever possible I design without brick, then don't need to employ bricklayers. Of all the trades I find them to be least knowledgeable or interested, yet see themselves as skilled snd special. Years of being in demand I suppose. I speak of SE England. I know there are good bricklayers, rightly very busy.

[naf123]

I'm in a similar situation . My garage conversion has an existing dpc and I need to work out how to connect the dpm to the dpc after the floor slab is poured . I think after trimming the dpm around the screed perimeter , apply few coats of liquid dpm (or silicon mastic) between the floor wall joint should do the trick . Is that correct ? 

[Mike]

6 minutes ago, naf123 said:

I'm in a similar situation . My garage conversion has an existing dpc and I need to work out how to connect the dpm to the dpc after the floor slab is poured . I think after trimming the dpm around the screed perimeter , apply few coats of liquid dpm (or silicon mastic) between the floor wall joint should do the trick . Is that correct ? 

As above - https://forum.buildhub.org.uk/topic/33449-dpc-not-lapped-as-specified-by-architect/#elComment_492131

 

[naf123]

Just now, Mike said:

As above - https://forum.buildhub.org.uk/topic/33449-dpc-not-lapped-as-specified-by-architect/#elComment_492131

 

Thank you . I'm a novice so still struggle to understand details in depth . So the dpm will run up the wall . Pour the slab. Let the slab dry. Pull down the dpm away from the wall and paint few coats the gap in there with liquid dpm....Then trim the dpm just above floor level . Is that correct ? Appreciate your reassurance. 

[Mike]

14 hours ago, naf123 said:

So the dpm will run up the wall . Pour the slab. Let the slab dry. Pull down the dpm away from the wall and paint few coats the gap in there with liquid dpm....Then trim the dpm just above floor level . Is that correct ?

More-or-less

 

If your polythene DMP will be below the concrete slab, then after pouring the concrete, trim the polythene off a few mm above the slab. Then paint the Aquaseal over the slab-polythene-wall junction (so it will also overlap the top of the slab by at least 100mm) and allow it to trickle down into the junction to fill any small gaps, then paint it up the wall and over the existing DPM. Before the final coat fully dries (it will be tacky), throw some dry sharp sand onto it to provide a key for the plaster / next layer.

 

Check the manufacturer's instructions for the primer and number of coats & their thickness (m²/litre). And do discuss it with Building Control to make sure that they're happy in your particular case.

 

Edited August 12 by Mike

[naf123]

Thank you ! What about internal walls of the garage - Do they need sealing ? 

[naf123]

36 minutes ago, naf123 said:

Thank you ! What about internal walls of the garage - Do they need sealing ? 

Reason why I asked because lot of pipes (radiator etc ) on that internal side , it wouldn't be possible to seal . 

[saveasteading]

38 minutes ago, naf123 said:

internal walls of the garage - Do they need sealing ? 

Not in a garage.

  But you have a radiator in the garage? Not really a garage perhaps?

[naf123]

Sorry it's a garage conversion . The house was replumbed few years ago and there are radiator pipes on one wall of the garage to go upstairs etc  anyway that garage will become a room soon . 

[Mike]

2 hours ago, naf123 said:

What about internal walls of the garage - Do they need sealing ?

Below the DPC they need sealing against moisture as above.

 

Above the DPC it's airtightness that you need to seal against. If it's being plastered you only need to seal the junctions with windows, doors, ceiling etc. If plasterboard (or just painted brick/blockwork) then you need a 'parge coat' too. There are already other threads on these topics.

[naf123]

I'm thinking of moving away from screed toward t+g boards (22mm moisture resistant) especially as it's a small room . Does the same principles above (re liquid dpm to wall joints with dpc) also apply to a t+g floor?  Thank you ! 

[Mike]

On 13/08/2024 at 00:46, naf123 said:

Does the same principles above (re liquid dpm to wall joints with dpc) also apply to a t+g floor?

Yes, if you're using engineered timber boards or chipboard (the latter I guess, as you say '22mm moisture resistant'). Just make sure the DPM's not damaged. That shouldn't be a problem if you lay it on an underlay, allow adequate expansion gaps at the edges, etc.

 

For solid timber boards, which seem these days to get glued to the concrete, that could be a problem at the edges if the boards lift & take the DMP with it. I'd probably plug & screw battens to the floor and fix the boards to the battens.

 

[naf123]

7 hours ago, Mike said:

Yes, if you're using engineered timber boards or chipboard (the latter I guess, as you say '22mm moisture resistant'). Just make sure the DPM's not damaged. That shouldn't be a problem if you lay it on an underlay, allow adequate expansion gaps at the edges, etc.

 

For solid timber boards, which seem these days to get glued to the concrete, that could be a problem at the edges if the boards lift & take the DMP with it. I'd probably plug & screw battens to the floor and fix the boards to the battens.

 

Thanks . But battens to the floor will probably damage the DMP. I thought the concept of a floating floor was no battens. Thanks !

[Mike]

16 hours ago, naf123 said:

I thought the concept of a floating floor was no battens.

It is. I just wouldn't do it if you choose solid timber, instead of chipboard or engineered timber.

[naf123]

So just to double check , So on top of the insulation (and VCL)  I have two options 

1. A floating floor of 22mm t+g and lay whatever flooring on top of that . Or lay engineering timber direct into VCL. 

2. Lay a floating batten on top of the VCL and then lay solid timber flooring on top of that ? But would that introduce an air gap under the solid timber ?

 

Thanks !

Edited August 16 by naf123