In message , Tim Watts
writes
On 28/05/2019 22:16, RJH wrote:
I'm looking to improve the ventilation to a suspended timber floor
with some new vents - they'll open to an outside path that has built
up over the years to near internal floor level.
I see there's these 'periscope' type things:

https://manthorpebuildingproducts.co...l-extended-und
erfloor-vent But it seems to me they'd take a fair chunk out of
the 9" solid brick walls, and the air flow doesn't look that good.
Would flat letterbox-sized grilles over a say 10" deep 'pit' feeding
a horizontal cut through the wall below the existing floor work?
I can see the issue of debris falling in, but if the grilles are
reasonably removable I can't see that being a dire problem. If it is
doable, is there a source of grille/conduit - can't seem to see
anything online.


I've seen "pits" down the side walls of houses with a conventional vent
in the wall 6" or so down. Older houses mind, but as long as the pit
cannot fill with rainwater, it's a solution.

We have those. The exterior ground levels are well above damp course so
I put a pea gravel french drain round the entire house. The suspended
floor vents are protected by concrete edging. They gather a few leaves
but not much of a problem.


--
Tim Lamb