Replacing an entire course of bricks

[Student]

Hi

I've discovered that my bottom two courses of bricks on my original rear extension (Victorian terrace) have mud / dirt between them instead of mortar!! This is in the slate DPC layer and the course above. The cause I assume, is that the previous owners had built the external ground level 20mm above the DPC and fitted a large concrete plinth along the bottom for good measure. ?

I'd be very grateful for some bright ideas on this but my current plan is to replace the entire width of the wall in 2 brick width sections (including the slate) and mortar new ones back in. The plinth is gone and I plan to lower the ground level outside. My main concerns are:

- Can I put a new, plastic DPC in, in overlapping sections or will the breaks in DPC make it pointless? I can use injection DPC if needs be but it seems overly expensive and time consuming if I'm replacing the bricks anyway.
- I need to fix chemical anchors into one of the courses at 350mm centres for a ledger plate. I was quite comfortable with the existing solid bricks but if they are replaced with perforated engineering bricks, are those compatible with chemical fixings or should I try and source solid bricks?

Really appreciate any help on this.

Edited June 19, 2019 by Student

[nod]

It is difficult and time consuming to insert a pvc damp course

A better option would be to rake out the effected joints and use a cream dpc such as dryzone 

I been using this product for about ten years and found it to be very effective 

[Student]

Yes, I wouldn't dream of inserting a PVC DPC otherwise, but as I'm taking out the bricks, I thought it might be OK and save me over £100.

[Ferdinand]

If it is structurally sound (?) would not one of those mechanically inserted DPCs (with a saw) be a better proposal?

 

Replacing bricks 2x2 like Noah's Ark sounds ... hard labour.

 

Ferdinand

 

 

[Student]

Not heard of mechanically inserted DPCs, do you have an example? I was thinking that as I'm taking bricks out it'll be easier to slip sections of DPC in with overlaps? If they need to be sealed, then that's more tricky. Might be better off with injection DPC.

 

Yes it will be a lot of faff, but I'll do alternating 600mm sections, so can hopefully do it in two visits but then again, I'm usually overly optimistic about how long this takes, it'll probably be weeks of work. Heartbreaking when I originally thought I might have to rake the odd dodgy looking joint out. ? I honestly think it would have been easier and less faff to rebuild the house from scratch! 

Edited June 19, 2019 by Student

[ProDave]

I always thought slate was the bees knees of damp proof courses.  At least that is what the surveyor told me when I bought our  previous 1930's house.

 

I suspect the bricks on top of the slate may have been laid dry?  And mud has got in through being covered.  I would start by pressure washing a short section, let it dry out and have a good look.

 

My experience was a slate DPC that was bridged with soil and hence causing damp issues, once cleared and left to dry out, no further damp problems occurred.

[Ferdinand]

Quote

mechanically inserted DPCs, do you have an example? I was thinking that as I'm taking bricks out it'll be easier to slip sections of DPC in with overlaps? If they need to be sealed, then that's more tricky. Might be better off with injection DPC.

 

Here is an explanation

 

https://www.dampcoursing.com/physical-damp-proofing-installation/

 

[Ferdinand]

And here is the BRE relevant Guide.

 

https://www.isse.org.uk/sites/default/files/2018-08/3.%20Rising%20Damp%20in%20walls%20-%20Bre.pdf

 

 

[Carrerahill]

6 hours ago, Student said:

Hi

I've discovered that my bottom two courses of bricks on my original rear extension (Victorian terrace) have mud / dirt between them instead of mortar!! This is in the slate DPC layer and the course above. The cause I assume, is that the previous owners had built the external ground level 20mm above the DPC and fitted a large concrete plinth along the bottom for good measure. ?

I'd be very grateful for some bright ideas on this but my current plan is to replace the entire width of the wall in 2 brick width sections (including the slate) and mortar new ones back in. The plinth is gone and I plan to lower the ground level outside. My main concerns are:

- Can I put a new, plastic DPC in, in overlapping sections or will the breaks in DPC make it pointless? I can use injection DPC if needs be but it seems overly expensive and time consuming if I'm replacing the bricks anyway.
- I need to fix chemical anchors into one of the courses at 350mm centres for a ledger plate. I was quite comfortable with the existing solid bricks but if they are replaced with perforated engineering bricks, are those compatible with chemical fixings or should I try and source solid bricks?

Really appreciate any help on this.

 

Do you have a damp issue and does it feel solid, if solid and no damp leave it alone. Are you sure it is mud between them? Could it be damp lime?

Edited June 19, 2019 by Carrerahill

[Ferdinand]

I think the first thing to do here is work out how far up your walls are damp so you can monitor it. Moisture meter. 

 

Start by by lowering the outside ground level back to where it should be, leave it for some time eg until next spring, and see if you need to do any more than repoint.

 

Do the necessary. Ideally the necessary will require you to sit on your bottom. Potentially you could backfill your trench with some decent sized gravel, or start the serious business of DPCs.

 

DPCs are not that expensive to install, and personally I would see that as a painful saving.

 

Ferdinand

Edited June 19, 2019 by Ferdinand

[Russell griffiths]

I think you may find it is not dirt and soil but, lime mortar the house would have originally been built with this and the raised soil level has kept it damp so it look squishy 

if the slate damp Course is intact then leave it there

rake out all the joints that are soft and re,point

re render a skirt up to damp course level, but don’t bridge the damp course. 

If it ever stops raining you will probably notice it drying out with the render hacked off. 

 

[Student]

Thanks for the info, that's really helpful. It seems like they are pretty much going about DPC insertion the same way, except they are not taking the bricks out completely.

 

It's definitely mud. I've mixed up and used lime mortar for brick repairs and repointing at the house and this is nothing like it. Brown, clay, smells like mud too. The room has been empty for some time but so hard to comment on damp but the plaster on the wall was blown when I bought the property. They had plastered all the way down to the crappy concrete floor, so it's hard to tell if it was the plinth bridging the DPC on the outside or plastering to the floor on the inside that's caused it.

 

I don't particularly want to risk the 'wait and see' approach when I can already see a problem that can be fixed. Reducing the outside level is going to take a while, so the most effective solution seems to be inserting a new DPC at a higher level. I'm happy to do the work, even if it is arduous, for peace of mind. My main concern was the installation of the DPC and use of perforated bricks. I've found that you can overlap the DPC 100mm and use sealing tape, not doubt it'll be fiddly. Also, Jewsons sell a solid clay engineering brick, which I may go ahead and replace the existing bricks with where damaged. These bricks are slightly smaller than the originals though; https://www.jewson.co.uk/building-materials/bricks-blocks/bricks/engineering/products/BRENG081/clay-engineering-brick-class-b-red-solid-brick-65mm/ 

Edited June 19, 2019 by Student

[Temp]

I don't see any issue overlapping the DPC in sections. It's frequently done at the corners of buildings and when a roll runs out.

[Temp]

 

http://www.icopal.co.uk/Products/Structural_Waterproofing/Damp_Proof_Course/DPC_Installation_SiteWork/DPC_Installation.aspx

 

Quote

 

All joints between lengths of damp proof course must be by overlapping the DPC a minimum of 100mm and must be sealed using Xtra-Load DPC Jointing Tape.

[Brickie]

Have you got any pictures? 

And have you drilled any sections out?

i find it hard to believe any section of walking was built using mud instead of mortar. 

[Student]

I can take some photos this evening. I've taken two bricks width out and inspected the bricks. I agree that they wouldn't have used mud as mortar but at the very best, the mud has mixed with the mortar. I can't see why it would be brown otherwise?