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My house was valued for a recent remortgage (which is now completed) and it highlighted a few things. One of which is the need to improve ventilation under the ground floor.

The surveyor says the rear of the building needs an air brick. I've attached a picture of the area I've got to work with and need to ask is there a right or wrong way to replace some of the existing bricks with an air brick? For example, in relation to the damp proof course?

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I'd not be happy putting an airbrick so close to ground level. If it rains heavily you could end up with the airbrick becoming a drain and wouldn't be good. Maybe send the surveyor a pic of the situation and ask him to write a letter back to you stating that it's acceptable. I have a feeling that he wouldn't want to put it in writing though.

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Hmm, good point.

The surveyor was being very thorough for the valuation. Which was good in a way, as I learnt that a few jobs need looking into. (Nothing serious.)

The few things he did mention seemed to have no impact on the mortgage companies decision to supply me the money. He dropped £1000 off the value of the house.

He said it was work that could need doing some time in the future; especially if I was selling, as a buyer's surveyor may pick it up.

However, there is very little room to insert an air brick, as you can see from the picture.

I was planning to flag the yard and if I did it on top of the concrete it would make matters worse. So it looks like I may have to remove the existing concrete base and maybe remove some top-soil prior to flagging, to allow an air brick to be put in.

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The airbricks should be built into the external wall above the finished ground level to prevent rain /snow water from entering the ventilator. They would usually be positioned at a similar level to the ground level DPC.

So in your case placing it the same level as the chemically injected DPC will not be a problem. Chemical injected DPC is just a water repellent that coats the pores in the brick / mortar to stop capillary pull and the dampness rising and not an actual physical barrier. If you replace the treated brick with a terracotta or plastic air brick the air brick does not need to be treated as it does not contain the same pores. (I am not a fan of chemical injected DPC as a remedial treatment along with the BRE and RICS)

You can accommodate a higher placement of airbrick with telescopic / flexible cavity tubes which usually accommodate up to 5 courses of brick between the internal and external vents.

How old is the house?

If built after 1900 then it should have airbrick and possibly an original DPC (late 1900's) they may be blocked by a rise in the outside ground level at some time. I would definitely removing the concrete before flagging most damp problems I come across at work are caused by an increase in outside ground levels.

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