Concrete drainage slab confusion.

[LukesLog]

Hello,

As part of my war on damp in our 1850s solid brick cottage, I've spent the last 2 days pulling up crazy paving patio stones in the front garden, as the ground level is a couple of inches hire externally compared to the interior.

Ive got to the stones against the house this evening, to find what seems to be some form of concrete or stone slab against the house, coming out around 1m or so from the wall.

This wouldn't have been a problem, as id still be lowering the exterior a good 15cm all round even at the level of the concrete, but it seems it raises up on either side, clearly designed to channel water into the gulley(which itself just puts out to soil at around 1ft away from the wall.

I fear I already know the answer to this, but am I going to have to pull up this concrete? If so, am I risking unsettling the footings of the house, particularly with power tools?

The plan is to grade the soil away from the property, then gravel over the top of a membrane.

Thank you.

 

[Kearn]

The grading plan is sensible…

The concrete may not need to be shifted if levels can be maintained and you cover with gravel to limit splashback against the walls.

However, if you have a damp issue. I would be removing the bitumen covering on the lower bricks and moreso, what appears to be a cement render on the outside.

But, it’s probably wise to take a few large steps backwards before investing time, energy and money and get the bigger picture clear. the questions really are - what symptoms of damp do you have? what are the internal wall coverings made from inside? and where is the moisture originating from…

 

[LukesLog]

The grading plan is sensible…

The concrete may not need to be shifted if levels can be maintained and you cover with gravel to limit splashback against the walls.

However, if you have a damp issue. I would be removing the bitumen covering on the lower bricks and moreso, what appears to be a cement render on the outside.

But, it’s probably wise to take a few large steps backwards before investing time, energy and money and get the bigger picture clear. the questions really are - what symptoms of damp do you have? what are the internal wall coverings made from inside? and where is the moisture originating from…

Thank you Kearn, I will know what the levels are like tomorrow when I pull up the last few stones towards the gable end.

If I remove the bitumen, is there a breathable paint or solution to covering the exposed courses?

Regards the wider damp issues, I should have mentioned in this post, that I have several other posts detailing my on going attempts, which include (but aren't limited to) removing internal gypsum and concrete render from the downstairs walls, fixing leaking roofing and resealing windows.

The exterior concrete render is staying for now, purely on a cost basis(we moved in a couple of months ago so things will be tight for a while). My hope is that the other remedial work will still be a huge improvement, particularly making the interior side of the external walls breathable(likely a lime base covering with wood board middle and lime outer skim.

Thank you again.

 

[Kearn]

Nothing wants to go on the bricks, exposed is good, it allows the moisture to evaporate off them. If it’s aesthetic, then limewash or a lime render, but it will get dirty down there and serve no real aesthetic benefit.

I feel the stages of work and cost bit! Yes making one side of the walls better will help, although the outside is usually the best place to start for maximum impact, as that’s almost always where the source of moisture is getting in and trapped.

Good hat and boots, always the most important priorities, plus rainwater goods and drainage.

 

[LukesLog]

Thank you Kearn, much appreciated.
If I could have done one big item, it would certainly have been the exterior render!

To cast further confusion on this concrete, it looks like im not seeing a brick course at all, but perhaps a concrete render across it?

If so, I fear the work i have just done is pointless as the bottom course still isn't free to breathe!

 

[LukesLog]

I'd welcome any reccomendations for a contractor/specialist to remove this in the Cheshire/NW area. I really wouldn't trust a 'generalist' to remove concrete from what will inevitably be very damp and soft red brick, particularly this close to the footings.

Thank you.

 

[a twig]

Your situation is very similar to mine here:

A

Thread 'Hotel Dampifornia'

Aug 12, 2023

You can check out but you’ll never leave!

So, sadly had to sell our forever home in Somerset - moved to a newer house supposedly with no problems. Didn’t bother with a survey as have got bored of paying for ever more inventive works of fiction and so moved in to inevitably find daaaamp in the old section of the house that dates back to 1860…

The previous owners were kind enough to share the survey they had done when they purchased which said there was no DPC in the original building and also there was no asbestos anywhere in the building.

Having found asbestos in the building not long...

• a twig
• Replies: 26
• Forum: Projects

• 

When I cut back the lower part of the render it revealed the original slate DPC and the render / bitumen had effectively been bridging it - sorting that out (repointing the now exposed brick and putting in a bell mouth at the bottom of the render above the DPC) along with fixing the blocked gulleys / downpipes resolved all the damp issues in the house.

 

[a twig]

Where the ground levels were too high I used a Zebcolm trench when I re-did the patio