How to 'retrofit' underfloor ventilation in 1901 terrace

[drpepe]

There is no route for airflow between the airbricks located in our front room (3 in total) and our hall or rear dining room due to the internal walls. The internal brick walls are built on wider 'foundation walls' (~5cm in height from ground level) and the joists are ~5cm above this. The underfloor walls are built up to floorboard level in the doorways, too.

my screwdriver sat on the foundation wall for scale - not much room between joists and foundation wall
View media item 79416The internal lounge:dining room wall is to left of the picture:
View media item 77340
I want to drill ventilation between the rear/front room and hall front/room - what is the best way to do this (or to get a builder to do this) ?

My idea was to drill holes and put short length of 32mm or 50mm plastic pipe through at 50 cm intervals (less / more) ?

Will this affect the integrity of the walls above?

Any other ideas?

 

[geraldthehamster]

Does the dining room have air bricks to the back of the house?

Do you actually have any signs of a damp problem in the dining room or hall?

Cheers
Richard

 

[drpepe]

Does the dining room have air bricks to the back of the house?

Do you actually have any signs of a damp problem in the dining room or hall?

Cheers
Richard

Hi - thanks for your reply.

The rear of the house suffers from the big conservatory - there is just one airbrick in the rear right corner of the dining room:

View media item 77344
Several damp-related issues:
1) Bad damp smell in the downstairs rooms
2) Damp soil very close to/touching the joists and wall plate in places.
3) Fungal hyphae growing in various places under the floor
4) High humidity (~80%) - this is quickly reduced by opening doors and windows (in the summer), so it seems to be affecting the house via lack of underfloor ventilation.
5) Damp meter detected in interior and party walls.


We wish to firstly sort out the smell by doing the work I suggested, plus an airbrick in the front of the hallway as this is the worst affected area for damp soil/smell/rotten joists.

If the ventilation gets rid of the smell (and fungi) then the next stage is a new dpm/joists and probably a new suspended floor with insulation (floorboards pretty grotty already - even before doing all the work)

I guess that the lack of decent ventilation at the rear will probably be an issue - options at the rear are :
1) increase the size of the single airbrick
2) channel ventilation into and through the concrete conservatory floor
then re-tile. This is expensive (and should have been done when the conservatory was built!)

Any suggestion or comments greatly appreciated

 

[drpepe]

Hi all.

Discussed the situation with a builder, he's going to come and install a bigger airbrick at the back, one under the front doorstep and knock out 3 bricks between hall/lounge and 3 between lounge/diner (under the floor obviously).

Given that the single airbrick at the rear is a major limiting factor to ventilation, is it at all possible to divert and use the draw from the (unused) fireplace to vent the subfloor up and out of the chimney?

 

[theprinceofdarkness]

Using a chimney will give you brilliant air flow. The problem is to get from the inside of the fire place out and under the floor boards. I have actually done this. You have to "dig" a trench through the hearth stone, say 5" deep and 4 " wide, put a bit of 4"* sewer pipe in trench , bed it with a strong mortar with 1" of mortar cover on its top.
Frank
* 68mm drain pipe might do.

 

[drpepe]

Using a chimney will give you brilliant air flow. The problem is to get from the inside of the fire place out and under the floor boards. I have actually done this. You have to "dig" a trench through the hearth stone, say 5" deep and 4 " wide, put a bit of 4"* sewer pipe in trench , bed it with a strong mortar with 1" of mortar cover on its top.
Frank
* 68mm drain pipe might do.

Thanks for that.

So there is no direct connection from the subfloor to the flue? Just a hole in the hearth that connects down to the subfloor?

How did you finish the fireplace -is the fireplace boarded up?