Sub floor Humidity Issue - Best method to solve?

[Loofah]

I guess the forced air could be argued but you'll always have eddy currents so doubt it's worth the outlay and effort. Personal choice!
Z vents on 4&5 - can you access enough to fit them? I'm lazy so I'd not fit them and make sure I add decent ones where I can access easily.
Clearing vents - there's a lot of blocked holes on the grates of the vent. Clean them out for better air flow. Also yes, get rid of any objects restricting air flow

 

[GeddyMortgage]

!
Z vents on 4&5 - can you access enough to fit them? I'm lazy so I'd not fit them and make sure I

I’d say there’s an inch (or two max) clearance between the joist and the inner skin wall where the gaps are for air bricks 4 and 5.

I’d assume “someone” would have to take out the course below the current gaps in the inner skin. Allowing the z duct to just slide in (tm).

Easy for 4. Harder for 5.

I’ll probably have to tackle this as a phased sum of parts and suck it and see.

Phase 1 being ….Ducting vent 1 to the property and pointing the drains at the rear near vent 4 would be the least effort. Could try that for a week.

if still bad, phase 2 would be Z vent 4/5, reinstate 6 or 7

Phase 3 - mechanical

 

[GeddyMortgage]

Bit of an update on this one. Had dyno-rod out to have a look at the drains. They couldnt get cameras down them but did unblock the drain by vent 3. (on photo below for refrerence)

They also put some illuminous green dye down each of the drains to see if that was seeping through to the subfloor. So back down the subfloor crawl-space again, I didn't notice any green dye but did notice this time the bricks lowdown in the sub floor by vent 3 do look damp. Video link below (apologies if the speaking is mumbled, had a mask on as it's fairly horrid down there)



Video - Sub-floor Damp bricks

As that drain was blocked.... if indeed it had been blocked for ages and had sitting water in there for a long time, could that be the cause of the dampness on the subfloor bricks in the video?

As if it was a cracked pipe / leaky drain, id have expected to see the green dye in the subfloor too?


thanks again,

Geddy

 

[Lore_illa]

The gullies are all salt-glazed clay. As is usual, they are all cracked and broken and leaking, and have been for years. The cavity is caused by the water turning the soil to mud and washing it away.

No point having them rodded, they all need to be dug up and replaced. You may find the underground drainpipes are also bad.

When digging, you may find the mortar has been eroded between the bricks (this is more common in old houses with lime mortar) and the cavities might have undermined the wall.

While you have your spade out, reduce the ground height against the wall. Finished height, including paving, should be at least two bricks below DPC.

Good luck!


P.s.
Do not allow anyone who sells silicone injections near your house.

Hi John,

We have just digged around our house and we have seen just what you mentoned, the mortar is gone across the bricks which were covered by tarmarc.

We are planning to point them, but we are also wondering whether we should keep digging a couple of courses more until we find the footings of the wall so we point those bricks as well. Is that common practice or pretty much out of sigth, out of worry?

 

[JohnD]

If it was me, I would expose and repair all the damage. Do not go below the bricks. Fill in at least the first foot afterwards and beat it down well to prevent the subsoil being softened by rain. If you can fill in the rest with pebbles, cobbles or large clean stone and rubble with no earth, it will carry less damp.