Confusing pointing problem - Pictures Added

[empty_vessel]

I've got a bit of a problem with my pointing (I think). House is 1889 3 bed semi of cavity wall construction.

I've had some damp problems in the front bay window in the past, mainly caused by dodgy guttering and a concrete pad outside that breached the old slate DPC.

I've removed the concrete pad but the whole area under where the pad was, about 2 courses of bricks above the slate DPC, the pointing is pretty much gone. Above where the concrete pad was has been repointed in a cement mix, with the associated blown/cracked bricks that comes with. The gable end of the house has not been repointed and is in a pretty sorry state, but not an emergency.

I'm still a little concerned about damp returning and want to get the pointing sorted, should I repoint just the very bad bit at the front of the house? What should I use? I know lime is right for the age of the house and type of construction but seeing as someone else has already used cement for the rest of the front of the house will it be ok?

I'm considering just getting the whole house done but that is obviously quite expensive! Would it be worth replacing the slate DPC too while I'm at it?

I can take some pics if you think it'll help?

Thanks for you help!

e_v

 

[gday2uk]

I would be taking a couple of bricks out first and making sure the cavity is clear. Poor pointing wouldn't cause the problem unless the cavity is bridged.

 

[Blagard]

Is the year of the house build a typo ?
The slate DPC suggests it is as I would not expect to see a slate DPC on a house that old! Picures are always a good idea, we may see something you missed!

Slate is a perfectly good DPC material and provided it was bedded in the correct mortar should be fine.

I agree with gday2uk and would add.
Cutting out the low blown bricks and replacing them with an engineering brick or where above the DPC in a matching brick would be good for two reasons. One you get a nice tidy new brick and two, you may get a chance to inspect the cavity. The cavity itself should be filled to ground level so that bit is OK. Only take out and replace a few bricks at a time. Replacement can be tricky and you may end up putting more compo in the cavity yourself! - I watched a bricklayer doing it once and marvelled how easy he made it look. Have done it myself a few times but takes me ten times as long as I try to gauge the correct amount of mortar to put on the top of brick and the other faces without too little or too much so the brick slides in without pushing mortar into the cavity!

As for repointing, the rule is never use a mortar stonger than the brick. If it is cavity wall construction then repointing probably would not solve your damp problem. To repoint, do not simply face up the old pointing - Thats what Cowboy builders do and it will eventually just fall off. You need to rake out the joint properly and repoint - I would need to check specifications as to how far to rake out but would expect around 15 - 20mm. A repointing mix with lime is a very good idea.

A common cause of dampness is when bricklayers are sloppy and let compo (mortar) fall into the cavity. It can either fill up above the DPC level rendering your DPC ineffective or settle on cavity ties to bridge the cavity. Thus dampness in the outer leaf that would not otherwise be a problem gets drawn across to the inner leaf. Repointing in this instance may give some relief, but will not cure the problem.

 

[gday2uk]

My semi is 1897 and has slate dpc.
OP are you sure it's damp returing not an old stains / salts coming through? What remedial action did you take to the plaster work inside the bay?

 

[Blagard]

My semi is 1897 and has slate dpc.

Brilliant, no better way to know about that example of construction. So can you tell, is the wall on yours cavity? (which again I would not expect!) or is it simply a thick solid wall that the OP is confusing as cavity because of its thickness.

The OP may get a few clues from the brickwork bond as you won't see many headers in a half brick outer leaf. In a thicker wall there may be headers in the central wall area, even rows of headers if it was english bond. (Ignore headers at ends and below DPC)

 

[stuart45]

In some places it was quite common to use snapped headers to make a mock Flemish bond on cavity walls.

 

[Blagard]

stuart45

Absolutely right, thats why the inspection will only gives clues. the only sure fire way to be certain is to look into the wall itself!

My own house is all stretchers below a creasing tile course (render above) yet it is actually a solid 9" wall.

In hindsite prolly best to forget the clues and hack out a bad brick and look!

I regret that I frequently only had clues to work with when inspecting properties and old habits die hard!

 

[empty_vessel]

Sorry about the delay replying - my notifications didn't work properly. It is definitely cavity construction and there is definitely a layer of slate 2 courses up in the the wall. The date is taken from a stone set into the front of the house, so I'm assuming that's correct too.

The inner wall of the bay was very damp and so I took it down and rebuilt it, emptying the cavity of as much rubbish as possible (soil, dead birds, mortar). The bay was the re-plastered with a bonding coat and a top coat of normal gypsum plaster, there is only a very small area right in the corner of the bay that is showing signs of damp.

I'm going to take a couple of piccies when I get home tonight so will post them later this evening.

Thanks again for your help and I'll respond a bit faster this time!

e_v

 

[empty_vessel]

As promised, some piccies:

Untitled

• empty_vessel
• 23 Feb 2010
• 1

A wider view showing the cement pointing only down to a certain level, the remnants of the concrete that breached the DPC and the slate DPC at the bottom. There is only one course of bricks below the ground level and no foundations that I can find.

Untitled

• empty_vessel
• 23 Feb 2010
• 1

A close-in of the missing mortar and showing the slate DPC and some of the cement pointing around an airbrick.

Untitled

• empty_vessel
• 23 Feb 2010
• 1

A close-in of what I think is the original lime pointing on the gable wall of the house.

Thanks for your help,

e_v