Level threshold detail

[Azz00]

Hi everyone,

We have just had our bifold doors delivered and the builder will be fitting them on Sat.

I just want to make sure that I am 100% happy with there the DPM etc all go.

Below are a few photos of the extension so far which show the dpm that’s under the slab coming up next to the opening.

Am I correct to think that this DPM will get glued down to the outer bricks, then a DPC course layed out over the top and then the door cill goes on top of this? (Sketch below of what I am trying to explain)

Also, would you have the perimeter upstand in the door opening as I have shown?

Any help would be appreciated as always!

 

[Notch7]

I would just have the dpm go up vertically, not over the brickwork.

I hope you have measured the FFL lots of times! -flush thresholds are a nightmare TBH

 

[Azz00]

I would just have the dpm go up vertically, not over the brickwork.

I hope you have measured the FFL lots of times! -flush thresholds are a nightmare TBH

Thank you! I did originally draw it like that! So just have the dpc course on the outer and then run the Dpm behind the cill.

 

[Dereekoo]

as an aside, whats that airbrick doing there?

 

[noseall]

flush thresholds are a nightmare

Correct. Especially when customers forget they would like things such as floor coverings.

 

[Azz00]

as an aside, whats that airbrick doing there?

There is a basement across the front of the house that didn’t have adequate ventilation so while the floor was being dug out across the back we put some ventilation ducting in

 

[Azz00]

Correct. Especially when customers forget they would like things such as floor coverings.

Yeah I must admit it does worry me but we have measured up multiple times and we have already bought the tiles so we know the exact thicknesses

 

[Azz00]

Also, can anyone offer any advice on the type of screed we should use? Liquid or traditional sand and cement?

We should have about 70mm - 75mm depth for the screed once we have put the insulation down.

The room is about 35sqm

 

[Notch7]

Yeah I must admit it does worry me but we have measured up multiple times and we have already bought the tiles so we know the exact thicknesses

There is no room for error -especially if the floor finish is running through from an existing room.

Its not just height, but also level. Supposing existing is not dead level, the tiler has got to blend the height as he works across to the flush threshold. And it means the screeding needs to be spot on.

The other nightmare is customers that want those huge format tiles....

 

[Notch7]

Also, can anyone offer any advice on the type of screed we should use? Liquid or traditional sand and cement?

We should have about 70mm - 75mm depth for the screed once we have put the insulation down.

The room is about 35sqm

Depends on your required drying time.

Cementitious screed is good for that thickness. We tend to use Mapei top cem -you use it instead of cement. Ideally with a screed pump.

the screeder I use sets up a laser level and sets out his screed to that, the finish is always really good, much better than using long levels to transfer from section to section. With a laser you are always working off the original datum

 

[Azz00]

There is no room for error -especially if the floor finish is running through from an existing room.

Its not just height, but also level. Supposing existing is not dead level, the tiler has got to blend the height as he works across to the flush threshold. And it means the screeding needs to be spot on.

The other nightmare is customers that want those huge format tiles....

We have completely ripped apart and extended our terrace over the last few months. The back of the house is now all open but there is an existing door in from the hallway and double doors from the living room. So based on your advice I am leaving the screening to the professionals as I was tempted to give it a go myself.

Depends on your required drying time.

Cementitious screed is good for that thickness. We tend to use Mapei top cem -you use it instead of cement. Ideally with a screed pump.

the screeder I use sets up a laser level and sets out his screed to that, the finish is always really good, much better than using long levels to transfer from section to section. With a laser you are always working off the original datum

No massive rush for drying time. The rest of the house is still livable. Don’t suppose the guy that you use is anywhere near Sheffield?

 

[Notch7]

Don’t suppose the guy that you use is anywhere near Sheffield?

Im afraid not -he is based in South East.

35sq metres he would do in 3 hours.

I wouldnt advise having a go yourself.....5 tonnes is lot of material to do in 1 go!

 

[Leofric]

As far as the dpc and dpm are concerned Bldg Regs Approved Document C states the wall dpc should be continuous with the floor dpm.
NHBC Standards regarding ground floors state dpc's should be linked with dpm. There is also a diagram with a note 'dpc laps dpm '.

That isn't a fully level access detail though , not sure what you are trying to achieve with that threshold detail.

 

[^woody^]

The DPM as drawn is correct as then it creates a continuous barrier and is lapped by the DPC.

I know its not to scale, but that screed looks a bit thin to be placed on insulation. It would be better anyway, to put the insulation down first and the concrete on top to hold it down and no chance of it cracking the screed.

 

[wessex101]

The DPM as drawn is correct as then it creates a continuous barrier and is lapped by the DPC.

I know its not to scale, but that screed looks a bit thin to be placed on insulation. It would be better anyway, to put the insulation down first and the concrete on top to hold it down and no chance of it cracking the screed.

I would have to respectfully disagree with that. Lapped with the inner leaf DPC yes or just brought up vertically and trimmed off once the screed has gone off, not lapped to the outer leaf. As it's draw if any water tracks under the door sill or down the reveals it could run down into the insulation and floor slab.