UKC

We are in the process of dealing with the dampness in our entrance/ basement, and the biggest problem is that it is built into the bedrock at the back. There are layers of porous rock which are allowing the water to filter through. We had wondered about trying to excavate enough to put in a sump pump, but that is going to be a very major project and I'm not sure how possible it will be (there is no access for big machines round the back). 

I was chatting with some workies today who were doing another job in there for us and they mentioned curtain injection. Has anyone had this done? Has it worked effectively and what was the cost of getting it done?

We are just finishing dealing with waterproofing the space from the inside, we have tanked it and added membrane on the worst wall and putting in the undefloor heating, which will all help.

Oh, and we removed the internal doorframe which was buried into the subsoil?!!!! So  this internal door frame seems to have gone in before the concrete floor slab!! Unsurprisingly, this was rotten and wicking moisture up!! (I honestly can't understand how some of these things even happen in the first place!!)

If you are talking about grouting into the rock, success will be limited by the nature of the rock structure. It is likely that the discontinuities will be the primary permeability and success of grouting will depend on their characteristics. Even when used in construction, success is far from guaranteed. To inject grout you will need to be able to get a drill rig behind your house.

while it is possible, it is likely to be expensive and messy.

When you say built into the bed rock, do you mean you have a wall that is affectively like a basement and water is percolating through?

If so any kind of tanking or injection won't work. Any attempt to stop the water will just result in high static pressures leading to the tanking to fail.

1m head is one tonne per M2 at the base. The water will find a way. Jeff Goldblum. 

With basements you normally allow the water to freely percolate through, and you have a false wall with a void so water can drip down and drain or be pumped away. 

If the damp is from below then injection should work.

We had a wall lining that allowed water to enter a channel leading to a sump pump. The hole for the pump wasn't huge as the amount of water wasn't huge (but enough to be a problem). We plumbed the washing machine into the sump so that it ran regularly (important apparently) and allowed us to have the machine in the basement. As mentioned above, we were told that trying to keep the water out will fail unless it has another path.

Moved since - and now dealing with a garden disappearing under water after yesterday's torrential rain. I dug a ditch, now have a water feature and am waiting for the Sheffield beaver population to colonise it.

Brain wasn't working yesterday. The thing to search is "Type C cavity drain waterproofing systems"

The wall which we can expose is brick, I don't know if there is a void or not. There are enough things that the original builders have done that we look at with disbelief, so there is no way of predicting!!

The dampness is not super severe, so I presume there is some sort of mitigation in place but it's just not quite cutting it. 

We know that tanking alone won't be the answer, and drainage out the back has to be tackled too. We are also installing ventilation and heating, so trying to cover all the bases!

From HighChilternRidge response, it sounds like maybe the injection won't do it though. 

We are probably looking at multiple drains to try and capture it from all sides before it reaches the house. 

The solution I was referring to typically requires you to create a new void with a superficial layer. The phrase to search for is "Type C basement void drainage"

Example Here: https://www.newtonwaterproofing.co.uk/wp-content/uploads/2020/02/Newton-Bas...

The grey and white dotted panels have nubbins on them that creates the void behind them.