1930's Semi-Detached rising damp help

[RobDee]

Hi everyone


We've got a problem with rising damp in one of our rooms, which is next to a rain water drain which isn't connected to the main sewer line. This is being fixed but I want to treat and prevent. We're having the room renovated in about 3 weeks, back to brick and rebuilt.

I found a hatch in the floor where someone (presumably the person who re-wired the house), has been down there making a mess.

I've attached photos of the damp and the hatch exploration, and am looking for some advice please. The photos have compressed, the damp is only in the corner. The rest is actually shadows from the boards.

I'm planning on:
- Dryzone creaming
- Tank
- Underfloor insulation suspended using strapping under the joists
- Thermal boards on the walls
- Skim

The plaster that's on there is the old type, and has deteriorated and blown all over.

The patches seem to get darker when it rains.

What are your thoughts? I'm happy for you to rip me to pieces, my plan is based on reading and researching (which may be misguided).

I want to save money by doing the damp work myself, I'm not a professional but I'm competent.


Thanks guys
Rob

 

[Danny]

@irish_spread

 

[RobDee]

I've had a look down there, and it's pretty damp throughout.

The new air bricks should arrive anytime soon, I intend to replace the old terracotta ones and add another one for good measure.

I'm not looking forward to it, but there's a trip down there again in it for me to clean all the s**t up and clear the rubble to reduce the risk of extra moisture and aid air-flow.

I am however a little concerned on the overall foundations of the house with it being wet ground under there.

 

[irish_spread]

No such thingas rising damp, improve your underfloor ventilation, check on external ground levels and investigate drains. Pound to a penny if you hack off them damp areas you've got bonding plaster or similar

 

[irish_spread]

I've had a look down there, and it's pretty damp throughout.

The new air bricks should arrive anytime soon, I intend to replace the old terracotta ones and add another one for good measure.

I'm not looking forward to it, but there's a trip down there again in it for me to clean all the s**t up and clear the rubble to reduce the risk of extra moisture and aid air-flow.

I am however a little concerned on the overall foundations of the house with it being wet ground under there.

Also it is entirely natural for ground to be wet, unless you bought your house in the Sahara or similar.

 

[RobDee]

No such thingas rising damp, improve your underfloor ventilation, check on external ground levels and investigate drains. Pound to a penny if you hack off them damp areas you've got bonding plaster or similar

Thanks mate! Yeah, turns out I've got a drain at the side of the house that's not been connected to the sewer line for about 15 years! The guy, supposedly a builder, who did all the 'home improvements' on the house way back when didn't reconnect the drain when he installed a bathroom in the box-room upstairs.

In terms of improving the ventilation, I've removed the old brick vents in favour for some more modern ones. I've also turned 1 brick into 2 brick vents to aid air flow.

I'm going to get under the floor and clear out all the crap and replace the rest of the vents soon, and get the drain fixed.

I think I need to address the run off water around the house too as there's just no thought gone into where all the rainwater is going when it rains.


Thanks for replying!

 

[The Hobo]

your drain seems like it could be the culprit and the metal vent seems to be up side down check your block paving is not to high

 

[RobDee]

your drain seems like it could be the culprit and the metal vent seems to be up side down check your block paving is not to high

Hi Norman,

Thank you for your reply.

We've had another drainage guy round, and he said that drain is actually the old drain and doesn't have a purpose anymore.

Originally the downstairs bath and sink would have ran into it and away from the house via the old terracotta sewer line/waste pipe. That pipe is no more, and has since been replaced by a modern plastic system.

The point he made was: if he connected the rainwater drain, and if rain fell directly into that drain; yes it would drain away. However, what's happening to all the other ground water around the house and side of the house which doesn't make it to the drain? It's seeping into the ground. The driveway and block paving around the house aren't sloping into the drain, it wouldn't really be doing anything. And if it was his house he'd remove the old drain and fill it in.

What he advised was to pull up 1 row of bricks of the block paving from around the house, and clean out all the old damaged mortar and re-point and seal the brickwork. This might help somewhat but again it's not a total solution to the problem. He also advised I should run all the taps in the house, get under the floor and inspect everything looking for obvious signs of damaged or leaking pipes etc.

With regards to inside, I'm taking the room back to brick, DPC cream affected areas, lift up the floorboards to insulate (heat loss prevention and cost saving not to prevent the damp), vapour barrier, then lay the flooring down again, and thermal board the walls.

The plaster that's on there now is the old plaster, which is basically just brown sand now due to the age. I'm thinking once this is all off, the walls will breathe better and have chance to dry out?? Let's hope so at least!

At least with the thermal boards, water won't pass through the polystyrene insulation into the room.

 

[irish_spread]

Hi Norman,

Thank you for your reply.

We've had another drainage guy round, and he said that drain is actually the old drain and doesn't have a purpose anymore.

Originally the downstairs bath and sink would have ran into it and away from the house via the old terracotta sewer line/waste pipe. That pipe is no more, and has since been replaced by a modern plastic system.

The point he made was: if he connected the rainwater drain, and if rain fell directly into that drain; yes it would drain away. However, what's happening to all the other ground water around the house and side of the house which doesn't make it to the drain? It's seeping into the ground. The driveway and block paving around the house aren't sloping into the drain, it wouldn't really be doing anything. And if it was his house he'd remove the old drain and fill it in.

What he advised was to pull up 1 row of bricks of the block paving from around the house, and clean out all the old damaged mortar and re-point and seal the brickwork. This might help somewhat but again it's not a total solution to the problem. He also advised I should run all the taps in the house, get under the floor and inspect everything looking for obvious signs of damaged or leaking pipes etc.

With regards to inside, I'm taking the room back to brick, DPC cream affected areas, lift up the floorboards to insulate (heat loss prevention and cost saving not to prevent the damp), vapour barrier, then lay the flooring down again, and thermal board the walls.

The plaster that's on there now is the old plaster, which is basically just brown sand now due to the age. I'm thinking once this is all off, the walls will breathe better and have chance to dry out?? Let's hope so at least!

At least with the thermal boards, water won't pass through the polystyrene insulation into the room.

The guy was correct about taking out the course of paving bricks that butt up to the house. You should also dig down a foot or so and fill with pea shingle. This is known as a French drain and allows surface water to drain away from the building.
While the polystyrene on the thermals is "waterproof lol" , the bonding adhesive isn't and will eventually fall off.
Wouldn't bother with doc injection, render with sand and cement containing water proofer and a salt neutraliser e.g. Sovereign rendermix from Sovchem then skim OR use a plastic membrane system.
The dampness won't be 'rising damp, it will be penetrating damp caused by external problems or the use of gypsum plasters

 

[irish_spread]

https://photos.app.goo.gl/u9tyBQjntDFRXGkQ8

A recent failed "rising damp" job

 

[irish_spread]

https://photos.app.goo.gl/461YNBmLorvy8apX7

Membrane system

 

[RobDee]

Thanks for the info - we had considered the membrane system up to 1m from the floor. I'll mention it to the builders, thanks.

We have damp on internal walls, one of which is the opposite side of the wall next to the drain.

The plaster used is basically like brown sand now, and it's blown in large slabs which will be coming off during the renovation. The moisture content is higher lower down towards the skirting too.

I'll do a french drain setup when I'm doing the rest of the remedial repairs to the bricks in the spring, and discuss the membrane system to the builders. I know there's a few top brands and less pricey brands, are they much of a muchness if I go with one designed to be dabbed?

Cheers

 

[Bagrat]

No such thingas rising damp, improve your underfloor ventilation, check on external ground levels and investigate drains. Pound to a penny if you hack off them damp areas you've got bonding plaster or similar

Totally agree with you poor ventilation drains could be blocked hack of all plaster let it breathe! Then plaster in quick lime .