Install air vent in previously Tanked basement?

[Sandt]

Hi

We've just purchased a Victorian flat with a tanked basement, fully decorated and being used as a study.

Our surveyor said it appeared in good condition, with no damp nor damage noted, but that we should consider installing some sort of ventilation system. He noted an odour but was sure it was coming from what was being stored down there, not from damp.

However having lived here for 3 weeks now, the sour smell isn't very pleasant so wondered if and how we install a vent, air brick or other.

The surveyor said Rentokil would give a 'top end' quote... But they won't help (i called them). A couple of other Basement conversion companies also said no thanks, as it was 'messling with someone else's work'.

Our sellers didn't put the conversion in, it was the owner before that (so about 7 years old). As such, we have no paperwork nor plans to verify the methods.

Plan is in my picture album. The diagonal shading is the ground floor and as you can see, the basement extends to the house's front doorstep at one end, and as far back as the centre of the hallway in the opposite direction.

Who do we call? I'm really at a loss of who to ask for a quote and what can realistically be done.

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• Sandt
• 14 Oct 2012
• 1

Basement, back wall

• Sandt
• 14 Oct 2012
• 1

 

[russellsmiler]

Little unclear as to your drawing, I am assuming the shaded area is the area of the basement below the ground floor!!

Asuuming the basement is completely below external levels you probably have a few option .

1. You could have a mechanical ventilation, vent axia or the like, this couldcome up through the floor (basement ceiling) assuming you have a place to hide pipework, into the above room and out to external wall, unless you have a hideway cupboard for 110mm diameter pipework you may consider a boxing in.

2. you could excavate externaly down the sde of the basement, core drill and sleeve ductwork, (rightly so if you have tanking then you would have to replace membranes etc) ideally wrap ductwork tightly in tanking membrane and make good joint againgst this with wall tanking. ductwork could go through 90 degrees and project above external ground level, you would need an incect,vermin, and weatherproof proof cowl on this, Inside basement you could have mechanical fan.

Based on a few assumptions them are possible answers, ideallyy though if you are extracting air from a room, be aware were the replacement air comes from...for vent axia domestic bathroom and kitchen fans make upp air usually just gets sucked under doors etc,

Let us know more if you wish

Russell

 

[Sandt]

Hi,

Thanks for your reply. Sorry that the plan is not very clear.

The basement is the shaded area on the plan, but doesnt eextens as wide across the property. It finishes in line with the doors you see in the middle. It's accessed by an open staircase from our hallway.

The rooms directly above the basement are the hallway and bedroom and the house is terraced. Therefore the only external wall that it meets (that's not a party wall) is at the front of the house. When approaching te house from the outside, you can see an air brick under the doorstep that has been filled in. Presume this was because of tanking?

With this extra info, would you still recommend option 1? And what kind of service should I contact? A builder, damp proofing specialist, air quality specialist or other?

Thanks.

 

[russellsmiler]

Ok Lets see if we can get this detailed right first!!

The photograph of the basement, were is the external wall in relation to the desk.?

Is there somewere convienient to run a vertical pipe inside the bedroom that will allow boxing in?

Could you determine were the floor joists are??

potentially if the joists are end bearing on the external wall this may allow you to contain flexi duct piping within the floor joists.

any chance of a photo of the external front wall, with an indication of the floor level of the bedroom, and possibly the ceiling of the basement, hopefully ceiling of basement is above ground level.

Russell

 

[Sandt]

Thanks Russell. I was travelling before so excuse any typos.

I have uploaded new photo * NB I can't seem to make the rotation work properly. So hope you don't mind tilting your head to the left! *

1 - Stairs down to the basement from our hallway. In front is the front of the house (where the external wall is). The door you see is the entry door to the flat. Imagine opposite on the left is the bedroom door.

2 - The funnel shape of the basement. At the end of this funnel is where is meets the external wall

3- Ceiling of basement = floor of hallway. The left hand wall of the basement (as when you walk down the stairs) lines up with the bedroom doorway, ie the basement extends further left than the hallway.

4 - Close up of the 'funnel' part. The green wall meets the external wall.

5 - External wall. You can see the air brick, although this is not visible from inside the basement.

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• Sandt
• 17 Oct 2012
• 1

2

• Sandt
• 17 Oct 2012
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3

• Sandt
• 17 Oct 2012
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• Sandt
• 17 Oct 2012
• 1

5

• Sandt
• 17 Oct 2012
• 1

 

[Sandt]

The basement is somewhat funnel-shaped, with a large square area
containing the main area of the room, and a much narrower area roughly
the same length again toward to the front end of the house. The
picture with the desk faces the rear of the house. The
farthest end of the 'funnel / bottleneck' section roughly (within a foot of)
meets the front exterior step, which must explain the air bricks in
the step. I think this is our best bet for a fan — it's the only
section of the basement with a clear section to the exterior wall, and
there's already airbricks installed in that exterior.

As there is a full ceiling in the basement, we can't see the
orientation of the floor joists, but I would be surprised if they
weren't in the correct orientation for installing our fan ductwork (ie
along the direction of the house).

I think our questions are:

What are the risks of puncturing the 'tank'? And can it be re-sealed
safely, even with a fan installed underneath the DPC? (We don't want
to install a fan if it will introduce the risk of damp or flooding)

What type of engineer/tradesman would we contact for this work? What would the ball-park cost be?

The odour seems to be coming from the floor of the basement in the funnel section, to the right of the stepladder which you can see in Picture 4. There's in built shelves here.

Thanks again.