Garage floor DPM at door opening?

[Discopotatoes]

Hi all,
I'm building my own garage and need a bit of advice.
I have got the footings in and the blocks upto DPC I'm about to dig out the over site and I'm not sure how to finish the DPM at the garage door entrance!
Do I Shutter it at the front, level with the blocks then bring the DPM up as you would around the walls? If so how do I get the required 150mm height above ground level? As the garage floor will be level with the drive and I will be installing a channel drain,
Cheers
Disco

[ATTAK Z]

Garages are usually constructed without a DPM ... you can of course install a DPM if you want to, but you will not be able to link it to the DPC as you would have to do in the building.

The 150 mm below DPC rule for paths is now a bit old hat at entrances due the the fact that the construction needs to comply with Part M of the building regs which demands a level threshold at the principle entrance. As a result there has been quite a bit of work done by several bodies to ensure that the DPM/DPC link is maintained. Take a look at the Visqueen website

[Spudler]

ATTAK Z said:

Garages are usually constructed without a DPM ... you can of course install a DPM if you want to, but you will not be able to link it to the DPC as you would have to do in the building.

The 150 mm below DPC rule for paths is now a bit old hat at entrances due the the fact that the construction needs to comply with Part M of the building regs which demands a level threshold at the principle entrance. As a result there has been quite a bit of work done by several bodies to ensure that the DPM/DPC link is maintained. Take a look at the Visqueen website

Ditto the above.

Personally I install a dpm to retain the water in the concrete rather than drain through the hardcore.
You could tank the block work upto dpc as you won't be lapping the membrane to dpc.
Backfill with gravel/hardcore rather than soil/clay and you won't have a problem.

[jonnydrama]

For all the hassle involved in installing a DPM I would do it, far easier to make it a habitable space in future.

I'm going to take the builders advice when mine is done but if I was doing it myself I'd set up a line of paving curbing before the slab is poured. I'd have the top of these at finished floor level and the dpm cemented to them like a typical dpc. Then once the slab was poured and everything has set I'd trim the excess material.

[ATTAK Z]

Spudler said:

Personally I install a dpm to retain the water in the concrete rather than drain through the hardcore ...

Agreed

jonnydrama said:

For all the hassle involved in installing a DPM I would do it, far easier to make it a habitable space in future ....

Agreed but in order to make it habitable you would need insulation as well ... and since the garage floor is (or should be) 100 mm below house FFL you will have the opportunity to add a linked DPM, 50 mm floor insulation and a 50 mm D49 reinforced screed on top of the garage floor when you need to convert the space to habitable ...

[Discopotatoes]

I think I should add, the architect specified the DPM and insulation the garage which is actually a two story extension on the side of my house is about 600 mm below the ground floor level as I live on a hill.
The main reason for my OP was because I couldn't see any way to tie the DPM to the DPC at the entrance and still retain a level threshold , I have found a fair bit of info regarding people retro fitting DPM after finding damp Ingress in the floor but nothing about the technical side at the entrance.
All that said I spose I should Speak to the building inspector Monday as ultimately he's the one I have to keep happy

Edited by Discopotatoes on Saturday 4th May 21:07

[ATTAK Z]

Three things

Asking for advice from the BI is good but you will have no comeback if he/she is wrong

Asking your Architect for a detail is also good and you will be able to sue if he/she is wrong

You can put DPC at more than one level i.e. use multiple DPCs

[jonnydrama]

ATTAK Z said:

Agreed but in order to make it habitable you would need insulation as well ... and since the garage floor is (or should be) 100 mm below house FFL you will have the opportunity to add a linked DPM, 50 mm floor insulation and a 50 mm D49 reinforced screed on top of the garage floor when you need to convert the space to habitable ...

I don't disagree in the slightest mate but I've just finished drawing all my garage plans and went through the same thoughts this fella is having. My end thinking was it's worth adding the insulation/dpm below the slab at this stage as it'll make a comfier garage to work in and will be easier to convert to habitable (solid block construction so can put up studwork with insulation) if that ever happens.

[jonnydrama]

Discopotatoes said:

I think I should add, the architect specified the DPM and insulation the garage which is actually a two story extension on the side of my house is about 600 mm below the ground floor level as I live on a hill.
The main reason for my OP was because I couldn't see any way to tie the DPM to the DPC at the entrance and still retain a level threshold , I have found a fair bit of info regarding people retro fitting DPM after finding damp Ingress in the floor but nothing about the technical side at the entrance.
All that said I spose I should Speak to the building inspector Monday as ultimately he's the one I have to keep happy

Edited by Discopotatoes on Saturday 4th May 21:07

Do you mean your garage finished floor level is 600mm below the house ground floor? If that's the case then your build is very similar to mine as I'm on the downward section of a hill. I've attached a pic of how I'm getting round this, the full length of the house wall I'm attaching to will be coated up to house DPC level. Where the two walls attach to the house wall the DPC will tie into the house DPC then drop down vertical until it's 150mm above the garage FFL. Inside the garage all walls will be coated in the RIW product shown in the sketch.

(The sketch is actually at the boundary end of my garage, pretend that the DPC shown is the house one!)

Edited by jonnydrama on Saturday 4th May 22:16

[ATTAK Z]

OP .... Do you drive a Disco and are you a potato merchant ?

[jules_s]

We dress the DPM up the outer face of the inner leaf and back in a block up.

Level access all around then as the external dpc doesnt have to be at the same level.

As for the threshold, you can carry the foundation through and bolt a big arse metal angle to it for a permenant shutter; dress the dpm below and up the outside of it

Job jobbed

[Discopotatoes]

jules_s said:

As for the threshold, you can carry the foundation through and bolt a big arse metal angle to it for a permenant shutter; dress the dpm below and up the outside of it

Job jobbed

This is the bit I'm stuck on and need details

[Discopotatoes]

ATTAK Z said:

OP .... Do you drive a Disco and are you a potato merchant ?

LOL!

[jules_s]

Discopotatoes said:

This is the bit I'm stuck on and need details

See the detail above?

Thicken the foundation up so the finished level is the same as the blinding....bolt angle to that

[Muncher]

I am trying to work out similar issues at the moment, it's funny how PH often comes up first in a Google search for things like this!

I don't really want to bolt anything to the garage door threshold to clamp over the DPC, are there any alternatives?

Also, how would you deal with this? My construction is going to be a single skin concrete block, set right on the edge of a concrete raft. The membrane is then to be folded back under the first block. The membrane then seems to be to be quite vulnerable at that point to any damage, only a small nick in it and I assume it will fill up with water. What's the best way of dealing with that?

[Spudler]

Shutter the edge of the slab so you have 2 or 3 courses of brick below finished floor.
Dpm or tray behind brickwork.

[Muncher]

Like this?



I can do that on two sides, but not on the other two sides as we are right bang on the boundary. I realise I might have to pull it away from the boundary but I would rather not unless there was no other option.

[TA14]

Muncher said:

I am trying to work out similar issues at the moment, it's funny how PH often comes up first in a Google search for things like this!

I don't really want to bolt anything to the garage door threshold to clamp over the DPC, are there any alternatives?

Also, how would you deal with this? My construction is going to be a single skin concrete block, set right on the edge of a concrete raft. The membrane is then to be folded back under the first block. The membrane then seems to be to be quite vulnerable at that point to any damage, only a small nick in it and I assume it will fill up with water. What's the best way of dealing with that?

a 10 x 10 chamfer? But won't you be in trouble at the garage door opening?

[Spudler]

Muncher said:

Like this?.

Nearly.
No stepping in with the brickwork. Build up as usual but you'll need to thicken up the slab under the wall.