Why do concrete floors need ventilation!?

thegentleway

Want to get patio up to threshold but I have some air bricks for ventilating cavity below floors. However I have beam and block so don't understand why I need ventilation in the first place?! 

Albermarle

Is there timber suspended floors in other parts of the house?
If yes and you have an extension with a concrete floor, it probably blocked off the original airbrick, so a route for the air had to be maintained.
One possible reason anyway.

thegentleway

Albermarle said:

Is there timber suspended floors in other parts of the house?
If yes and you have an extension with a concrete floor, it probably blocked off the original airbrick, so a route for the air had to be maintained.
One possible reason anyway.

It is an extension but only have suspended timber floor upstairs. All floors downstairs are concrete (Existing house is solid concrete and extension is beam and block). Existing house has no air bricks, just the extension. 

Eldi_Dos

I would imagine it is the void that is being ventilated not the floor.If you do go ahead with patio you  can construct a bund around airbrick so airflow continues.
Have you took account of DPC when considering patio.

thegentleway

Eldi_Dos said:

I would imagine it is the void that is being ventilated not the floor.If you do go ahead with patio you  can construct a bund around airbrick so airflow continues.
Have you took account of DPC when considering patio.

yes it's the void being ventilated! Which is obviously important for wood floors but seems completely redundant for concrete!

What's a bund sorry?

DPC: yep we're having a fall away from house and a drain along the house as well. 

stuart45

Block and beam floors are ventilated to prevent any build up of gasses. It's part of the regs.

thegentleway

stuart45 said:

Block and beam floors are ventilated to prevent any build up of gasses. It's part of the regs.

What gasses are going to build up!?

It is indeed part of the regs (hence why my builder put them in) but I don't understand why.

stuart45

There's a number of toxic gasses which come up from the ground, radon probably being the worst, but there are others, especially in brownfield sites or peat etc.

thegentleway

stuart45 said:

There's a number of toxic gasses which come up from the ground, radon probably being the worst, but there are others, especially in brownfield sites or peat etc.

Thanks for explaining; I didn't realise radon could get through concrete. 

jj_home_80

Yeah, it’s a bit confusing – even with beam and block floors, ventilation’s usually still needed. The void below is there to stop moisture build-up and help with airflow, especially in older properties. Blocking off those air bricks completely can cause damp or mould issues over time.

If you're raising the patio to threshold, best bet is to use something like vertical air brick extensions or telescopic vents to keep airflow without blocking them. Seen people do it without and regret it later. Worth doing it right the first time!

Eldi_Dos

thegentleway said:

Eldi_Dos said:

I would imagine it is the void that is being ventilated not the floor.If you do go ahead with patio you  can construct a bund around airbrick so airflow continues.
Have you took account of DPC when considering patio.

What's a bund sorry?

It is like a Dam that is consructed around front of airbrick to allow airflow to continue if ground level is being raised.
Not the best idea but sometimes needs must.They quite often get filled with leaves and stuff and need kept clear.