Re Injecting using old damp proofing holes...possible?

[Elder92]

Hi guys, this is my first post & i'm a new member so sorry if i've done anything wrong/this has already been discussed.

I am going to inject damp proofing fluid into the entire ground floor of my house to stop rising damp. It was done 20 years ago, but there is significant damp still present now (although the house has been neglected for a long time!).

Is it possible for me to inject the fluid into the existing damp proofing holes which has been revealed when the plaster was hacked off?

Thanks in advance[/b]

 

[patrocks]

I am not a damp proofer but modern chemical damp proofing is injected into mortar. Are your holes in mortar or brick? If 20 years old I suspect they are into brick which would rule out the majority of chemical DPC's.

 

[loply]

What makes you think it will work?

 

[gregers]

20 years ago then i would say they used a spirit based fluid,hence into the brick itself.if you do try again using a water based fluid then i would think it would need to be injected at 100-150 psi.

but are you sure you have rising damp.this has been YET again discussed recently on this forum with some good n bad arguments saying that is does not exist.
so i would suggest you make sure that if it is a cavity wall they are cleared of silt/crud,if its solid is there any pipes in or around leaking,are the outside levels too high?pointing shot?
the list is endless.
then once you have eliminated everything else then as you say it could be rising?

 

[Elder92]

The existing holes are into the brick, although the advice I have received elsewhere points towards injecting into brick and not mortar...?

Loply: I am aware there is a huge debate about whether damp proofing chemicals work & whether rising damp is a myth or not, so I was hoping not to get into that here if possible (I believe it will work, so will give it a go)

 

[Elder92]

Gregers: Clear cavity wall, no leaking pipes, outside levels maybe around 1 foot below internal floor joists, pointing is all good, new guttering....

IMO it would be worth spending a couple of hundred quid to re inject just to be sure, that way if rising damp is a real thing it can hopefully be ruled out and prevented

I know this has been discussed a lot, so i'm not looking to create yet another thread about it. I just cannot find anything related to whether I can use existing holes (which are at a good level for chemical injection), or if i must create new holes...

 

[Johnmelad]

http://www.askjeff.co.uk/rising-damp/
http://www.architectsjournal.co.uk/...a-myth-says-former-rics-chief/5204095.article
http://www.heritage-house.org/the-fraud-of-rising-damp.html
http://www.rics.org/uk/shop/The-Rising-Damp-Myth-17888.aspx
http://yorkshiretimes.co.uk/article/Rising-Damp-in-Old-Houses-Its-just-a-myth
http://buildingdoctor.com/rising_damp/rising_damp_myth.php

 

[gregers]

well if its been injected from the outside then that was a pointless exercise,that means they have treated the outside skin.then re-drilled through the cavity into the inside brick to re-inject.shouldve just injected the inside skin from the inside and cleared the cavities from there.
what about replastering?

 

[patrocks]

I am no expert but have been googling this plenty in the past and the current chemical systems are all into the mortar not the brick as this can be done without pressure.

I have my doubts over the need for a DPC (leaning towards good ventilation and pointing) but have had a chemical DPC installed this week as it isn't that costly and that was into the mortar.

I had this one done by an approved installer to get a "guarantee" but did my last one myself and don't think there is any difference. It isn't complicated. Choosing the best chemical might be harder. Dryzone was my chemical of choice..

 

[Elder92]

It's been injected on both the outside and inside skin, outside being capped and inside being rendered & plastered over.

I plan to inject the inside skin. The house is a renovation project so plaster & render has already been hacked off ready for fresh plaster & render anyway as it was damp.

Thanks patrocks, I will investigate the mortar/brick injection further to be sure it is done correctly. It would be a lot easier for me to drill into the mortar anyway, so that would be a bonus if it is the mortar that is injected!

 

[loply]

Hold on... You've got a cavity wall?

Where exactly is the damp manifesting itself? And how is it jumping over the cavity?

If it's not jumping over the cavity than it's coming from inside the property in which case you need to fix a leaking pipe, condensation problem, blocked underfloor air vents, etc etc, whatever is causing the inside of the property to get wet.

The proposition that your inner leaf of a cavity wall is damp because it's absorbing moisture from the ground seems pretty damn unlikely.

All the damp proof courses in the world won't stop stop water that's already inside your house from causing damp walls.

 

[Elder92]

I have both cavity and solid walls - which are bridged onto each other in some cases, however EVERY wall seems to be damp, not just where they are bridged.

I have cleaned all of the air bricks out, and there is no water supply in the property so it can't be a leaking pipe...

I must be missing something/ ill-informed here...but why is it not possible for damp to rise up an inner leaf of a cavity wall as it is still in contact with the ground? What would the difference be between the inner and outer leaf, that means it can only access the inner leaf if it is rising through the outer leaf and is then bridged across to the inner?

 

[loply]

If the ground your building sits on was so wet that the foundations had become completely full of water by absorption, and the inner leaf of bricks was now wet because it had absorbed the water from the foundations, you'd be a well beyond the help of damp proofing...

What's inside this building? What's on the walls and what's it got for ventilation? What's it used for? Is it concrete or suspended timber floor?

 

[Elder92]

Okay that makes sense.

Inside the building are suspended timber floors with around a 3 ft void. Air bricks are there for ventilation (around 4 for each room, with each room being an average of 4m squared). The brick plinths holding the timber floor joists are built with gaps to allow air flow. It it a house that is not currently occupied as it is being renovated. The walls were covered with render to around 1m high, all of which was plastered over. However this has since been removed, so bare bricks to 1m high.

I have noticed that the earth that the building sits on below the floor timbers has cracked like an egg shell, as though it has become saturated and dried out.

 

[loply]

What's the outside ground level like relative to the air bricks? Any chance rain is getting through them and soaking the ground under the floorboards?

You basically need to figure out how the water is getting inside the building. If it was solid walls and was rendered on the outside this may well have prevented the bricks drying out when they become wet from above and/or from internal condensation, in which case removing the render as you've done should be enough - just needs time to dry out now.

This could be ground level issues, drain/rainwater issues (gutter leaking into cavity or onto wall), failed pointing, possibly your render was causing an issue, etc.

In any case based on what you've said I can't see any possible reason to do anything involving another injected damp proof course, but if you get a damp proofer out they'll tell you that you need 6 of them, just sign here please, etc etc.