Telescopic Underfloor Vent retrofit questions

[mattwaddy]

So I've dug out my kitchen floor and now need to reinstate an air duct under it back to the suspended floor on the other side. There was previously a pipe across this solid floor to an airbrick on the external wall. Now I've dropped the floor level so the plan is to use one of these telescopic vents on both sides of the room joined by a standard 110mm drain pipe. I'll be putting the drain pipe into the MOT layer surrounded by pea gravel before wacker plating it down and doing the blinding sand layer and DPM. I do have a couple of questions though if someone can advise.

1.) Do these vents need to be recessed into the inner brick leaf? i.e will I need to remove bricks to fit this in or can it sit on the inside of the room? Same question for both the internal and external wall as there will be two of these

2.) Could I butt this up to the existing air brick that's there (two brick height), or will it need to be removed and a specific air brick face added to this?

3.) As this will essentially be under the floor and raised both ends due to two telescopic sections how can I best protect against any external rain / water ever getting in as it would potentially build up in the drain pipe assuming a seal is in place. Worth adding a couple of drain hole to the pipe to permit egress of water into the hardcore underneath?

Pics attached of another similar example and the area I'm taking about

 

[cdbe]

Why do you have to telescope the inner end? Probably better to make a new hole lower down if it still comes out in the void, and if you fall the pipe down a bit any moisture will run out and evaporate. At the outer end, personally I would knock out a bit of inner leaf otherwise it will intrude into the slab and interfere with your DPM. Using the existing airbrick makes sense.

 

[Deluks]

I had a similar problem, as suggested I removed a part of the inner leaf, although technically it was a 9" solid wall so I carefully chopped the bricks out.

This meant that the back of the periscope was nearly flush with the inside wall, I used a small piece of insulated tilebacker board over this to reduce the cold bridge and rendered over flush with the existing inner wall.

 

[mattwaddy]

Why do you have to telescope the inner end? Probably better to make a new hole lower down if it still comes out in the void, and if you fall the pipe down a bit any moisture will run out and evaporate. At the outer end, personally I would knock out a bit of inner leaf otherwise it will intrude into the slab and interfere with your DPM. Using the existing airbrick makes sense.

Yeah the entry point is at the lowest point of the suspended floor which has a layer of concrete 15cm under thr joists. I'll look to recess, the timco down section seems to be 45mm thick

 

[mattwaddy]

I had a similar problem, as suggested I removed a part of the inner leaf, although technically it was a 9" solid wall so I carefully chopped the bricks out.

This meant that the back of the periscope was nearly flush with the inside wall, I used a small piece of insulated tilebacker board over this to reduce the cold bridge and rendered over flush with the existing inner wall.

Thanks, 45mm is the thickness I'd need to get it flush. I guess angle grinder + sds to right depth and chop it out would be best?

 

[Deluks]

I can't remember how I did it, no grinder though, too dusty. I might have stitch drilled the bricks to 'cut' them and removed with a hammer and bolster.

 

[mattwaddy]

I can't remember how I did it, no grinder though, too dusty. I might have stitch drilled the bricks to 'cut' them and removed with a hammer and bolster.

Ah ok sorry you removed the brciks rathet than chased it in. I have a single brick inner leaf, cavity and outer brick leaf

 

[Deluks]

Ah, then build it in to the cavity, tray on top. Remove the bricks, install, and rebuild around it.

 

[mattwaddy]

Ah, then build it in to the cavity, tray on top. Remove the bricks, install, and rebuild around it.

Tray? I could perhaps do that on the external wall side, but the internal wall will only be a single brick layer and same issue

 

[Deluks]

Looking again, tray prob not necessary here. Looks like the air vents are below dpc anyway and will be behind your lapped-up-the-wall dpm.