Airbricks are below the desired finished ground level

[daiking]

I'm not even sure this question belongs here but it relates to a brick of sorts.

 

On one side of our house I'd like to have a patio area as near to the internal FFL as possible. In reality this will be, one brick below that level but effectively the same level as the DPC.

 

However, (isn't there always), there is are 2 airbricks along this wall and they are also under the DPC. One of the airbricks has a pipe through the slab leading to the original house suspended floor void, the other doesn't.

 

Without the airbricks I was assuming there was some sort of drain detail that could be used to bring the patio right up to DPC but I'm not sure of what detail I would need to adequately ventilate an airbrick that is 'below ground'.

 

The NHBC guidelines show a 600mm sunken area around the vent before raising the ground level - which would somewhat ruin a level patio.

[Ian]

29 minutes ago, daiking said:

On one side of our house I'd like to have a patio area as near to the internal FFL as possible. In reality this will be, one brick below that level but effectively the same level as the DPC.

 

However, (isn't there always), there is are 2 airbricks along this wall and they are also under the DPC. One of the airbricks has a pipe through the slab leading to the original house suspended floor void, the other doesn't.

 

We've got that same issue at home. It was resolved (by the original owners) with timber decking with an air void underneath which means there's no interruption to the air flow to the air bricks in the house wall.

[Onoff]

French drain?

[daiking]

7 minutes ago, Ian said:

We've got that same issue at home. It was resolved (by the original owners) with timber decking with an air void underneath which means there's no interruption to the air flow to the air bricks in the house wall.

We don't really want decking. Substantial groundworks to make it solid and close to a stream, we risk 'wildlife' under a deck next to the house

 

6 minutes ago, Onoff said:

French drain?

 

Assuming something like that along the wall but doesn't deal with the air brick. The other airbrick is under a door  how do we put a step there?

Edited May 24, 2017 by daiking

[Onoff]

Might be of interest:

 

http://www.1stassociated.co.uk/articles/french-drains2.asp

[Ferdinand]

What is your patio surface material?

[daiking]

9 minutes ago, Ferdinand said:

What is your patio surface material?

 

There isn't one yet but some sort of solid paving/stone unless we were to run out of money before getting there. This is my upfront planning to know what I need

[ProDave]

This is what I have done in the same situation

A small retaining wall made of railway sleepers. A French drain along the front with the level of stones lower than the air bricks.

 

In my case it will remain open like that. It's only along the front as the side and back the ground level has sloped down and it's not needed.  I will bridge across it when I form the ramp and path to the front door.

 

Could you do something like that with the paving slabs cantilevered over and keep the drain open at the ends for airflow?

 

 

[Ferdinand]

In a level patio clearly you need some sort of well to allow access to your airbrick, which could be filled with stones a la @ProDave and have a patio slab on top, or a slab supported on whatever the edgings of the well are.

 

Or you could use something like Adjustable Support Pads - perhaps four in your well:

 

 

Cost about £4-5 each. My entire patio is on them, but I have a slab underneath.

 

I think in your case I might lay a chunky paver below the airbrick level, then put pads on that to support the top slab. Access to the void is simply by raising the one loose slab.

 

You need to keep your under-patio material out of the well, and that could be bricks or breezeblocks around the edge, but I might be tempted to use strips of paver dug in as retainers, as you could for a raised bed.

 

The problems then are what to go under the patio to keep it rat free, and how to keep the air-brick-wells drained. Both seem soluble, but need careful thought.

 

Alternatively could a periscope vent be built into a hard garden feature?

 

Ferdinand

 

Edited May 24, 2017 by Ferdinand

[AliG]

We had a terrace built behind the house. They effectively extended the air bricks from the house wall to the steps up to the terrace using ducting, so there are now air bricks in the steps.

 

Assuming that the ground doesn't slope so you have a step up onto the patio then you should be able to duct the air bricks under the patio. If there is no step up I think you would need a well which will be a bit of a pain.

 

 

[daiking]

Someone said to me, "Why don't you just raise the air brick?". Which seems the obvious thing to do.

 

secondly does the base of a cavity wall need ventilating? Richard Head builder left space for an air brick under a door frame. It doesn't lead anywhere near the original house suspended floor. Just into the non insulated bottom bit of the cavity wall.

 

finished level will be approximately half way up the lowest brown brick, not the red engineering bricks.

Edited May 30, 2018 by daiking