Under floor ventilation

[ran1]

Hi All

I have a question regarding venting the underfloor. Thanks in advance for your time.

Here's an overview with my question at the end.


My house is a 1940's brick/cavity constructed semi without cavity insulation. Suspended wooden floor apart from solid kitchen at rear.

My question concerns the lower air bricks which sit on the DPC as viewed from outside and ventilate the cavity and underfloor via a missing brick internally.

There are 3 vents at the front, 2 gable end & 3 at the rear.

Only 2 (of 3) vents at the rear serve the underfloor as the kitchen has a solid floor.

External vents are 2 bricks above the internal vent, which is simply a missing brick bridged with slate.

When I'm under the floor I can see daylight through the gable & rear vents.

However the 3 vents at the front are just ventilating the cavity as the builder appears to have roughly mortered a brick on edge in the internal vent hole.


Getting back to it...


I'm unsure if the front internal vents (gaps) were bricked intentionally to create a specific airflow direction or to stop it being too draughty.

Admittedly I'm not having rot problems but I am doing repairs internally so thought I'd ask. I will also be having patio doors fitted so may loose a vent at the rear due to a step.


Can I remove one, or all 3 bricks, set on edge (internally under floor) at the front of the house and insert plastic airbricks to increase airflow?


Your views are appreciated...Thanks for your input

 

[JohnD]

there was a period when people used to ventilate cavities. That is no longer the practice. If you unblock the inside, and sleeve the hole, it will ventilate the subfloor better. It would need doing anyway if/when CWI was installed.

If you're taking the floor up, consider insulating between the joists, and especially round the edges of the room where dirt and draughts blow under the skirting, with mineral wool.

 

[ran1]

Not taking the floor up JohnD . Any work has to be done under the floor (nasty). Thanks for the input. Appreciated

 

[oldbutnotdead]

How big is the gap between joists and oversite? If up to 300mm someone young and slender can be sent down (you got any children?), if greater than 450 then a moderately agile adult could do a lot of work down there. Yes, ditch the blockages to the front airbricks, getting sleeves or anything similar in (so you aren't venitlating the cavity) will be a nightmare. Top Bodge for this job is eaves trays (or any other source of flat rigid plastic)- cut to appropriate length/width and glue/wedge in place