Wot no DPC?

[Feltwell]

So, Feltwell Towers, a brick-built lump of a place dating from 1899, is nearing the end of it's mammoth repointing activity. We're getting near the bottom of the walls - time to switch to the "Strong" mix lime mortar, recommended for works below damp proof course.

Now, running consistently right around the house is a distinctly thicker bed of mortar on one joint - this joint is at the top of the airbricks and directly underneath the bottom of the floor joists for those rooms with suspended floors - and I'd always logically assumed this was where the DPC is. But, this weekend just gone, we cut out some damaged bricks just under or above this level, and there was no evidence of any DPC. I'd assumed we'd find slate or possibly tar, but no, there's nothing. The brick above and below is the same, the original mortar likewise looks the same as everything around it - almost black with lumps of lime in it, I reckon it had a lot of coal dust mixed into it.

Now I'm not overly worried as there's no real damp issues here, save for one corner where we've lowered the ground levels to below where we thought the DPC was - and that's drying out nicely! This is also despite the previous haphazard combination of cement pointing in some areas and badly eroded original lime in others.

Out here in country-bumpkinshire I guess it's not impossible that a house could be built this late with no DPC, but it is very odd, especially given the distinctly thicker mortar bed.

 

[Flyfisher]

Seems strange to lay an extra-thick course of mortar in place of a DPC. Cowboy builders trying to make it look like a DPC was installed?
Though having seen your house it doesn't look like the product of cowboy builders.
As you say, very odd. Have you only checked the one place?

 

[Zebra]

Someone's nicked it?

 

[Feltwell]

That would be a very committed thief!

We've only actually taken bricks out in 2 places adjacent to the "DPC" - 1 in the front bay window wall that had spalled, and I replaced 4 on the front corner of the house next to the driveway, due to vehicle damage :roll: (Quite how anyone manages to reverse into a house is beyond me..... it doesn't exactly jump out at you.....Now watch me hit it next time! :lol: )

The "DPC" has been cement pointed all the way round but knock the pointing off and it's not obvious that there is anything there. I doubt it's bodgery as the brickwork here is of a decent standard, the house was well built I think.

I have read that hessian or jute was sometimes used as a DPC, I can't imagine it was very effective - maybe one possibility and it's rotted out?

This article - or perhaps more of a rant! (but a justified one) against the chemical injection companies - says that in Holland they don't have DPC's at all.

https://www.heritage-house.org/damp-and-condensation/managing-damp-in-old-buildings.html

I'm not overly worried as there is certainly no great damp issue here, more curious and surprised than anything. One thing is for certain, I won't be rushing out to buy a load of silicone mix and an injector and start drilling holes everywhere!

 

[Craig89]

And I was just about to suggest you get in touch with a "damp expert" for an injection DPC :lol: .

My house has the thick mortar bed at DPC level but it most certainly contains a thick row of slate all the way round. My house was also built with the coal dust in the mortar (it is a mining village after all) and although it makes it attractive and quite a bit stronger than straight lime mortar I don't think it effects its resistance to water

 

[Lime]

............

I have read that hessian or jute was sometimes used as a DPC, I can't imagine it was very effective - maybe one possibility and it's rotted out?

I think that is probably your problem, the damp proof material has rotted away.
They also used to use waterproof mortar/cement of some sort in and around the damp proof course, maybe that is what is stopping the damp now.