Mortar cracks - how to fix? (pics)
- Thread starter wedge69
- Start date
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You have to look closely on some houses to see it. Not everyone will agree it's the best method, but when it's bedded on you do sometimes see some really large, ugly joints at DPC.
This method is also used a lot by the Dutch and Flemish.
This method is also used a lot by the Dutch and Flemish.
Nice to see Stuart and 4x4 have some common sense.
And you are correct that some bco want to see the dpc, as they do in our area.
And you are correct that some bco want to see the dpc, as they do in our area.
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Then you still have a lot to learn then fellow. We disagree with a lot of the posts that woody writes, how ever in this instance he is near enough right to stop a possible reoccurring problem.
Always shake a thin bed on top of splash course before laying DPC
Always lay your DPC 5 to 8mm back from face edge.
Always run a brick along DPC to flatten bed down to 5mm.
Lay first course with standard 10mm joint and always have a heavy dinger in your bucket to joint DPC.
Regards damp percolating up over the face of the DPC joint, is a load of old cobblers.
oldun
40 years? .... and you still have not got it right?
Did you cover DPC's in apprenticeships back then?
You don't leave DPC's sticking out so that the BCO can check them. The DPC should be checked when it is laid before building any further, and it should be pulled back so that the 10mm bed joint can be seen to have no furrows, or voids and contains no pebbles etc. Checking a DPC just by seeing a few mm sticking out of a wall is not checking a DPC
And a DPC joint is 20mm (10 above and 10 below) and typically weather struck to denote it as a DPC ... and that is how you know it is there
And it is never ever left projecting into a cavity
This is all basic stuff.
And the challenge still remains .... have a look at all the buildings built since DPCs were first used and see how many have them projecting with cracked joints, and how many are pointed up. Obviously, certain parts of the Cotswolds are not included in this challenge as we will take it as read that they are constructed incorrectly
Oldun, we do lay the dpc on mortar, bco in our area insist on flush with brick, as for damp perculating above damp, this wasnt the original question asked by the poster.
He asked why the joint had cracked, Woody gave inaccurate reply, ie cut out the joint and cut the dpc back
The op didnt say he had a damp problem.
Woody your last statement has been copied word for word from one of your diy books.
He asked why the joint had cracked, Woody gave inaccurate reply, ie cut out the joint and cut the dpc back
The op didnt say he had a damp problem.
Woody your last statement has been copied word for word from one of your diy books.
could the joint just be cleaned up then a brown water proof mastic be squeezed in ?
Thanks for that Stuart.
Cant argue with NHBC
Cant argue with NHBC
Rake it out to 20mm use a 1:4 mix cement sand and add some waterproofing/ frost additive to it and you should be ok. but it is common for the last mm to shale up in this area and is not a problem if you can live with it.
Its done in all manner of different ways. B&Q warehouse near me is done with DPC visible all the way round. I built my extension with it protruding all round and trimmed off with a sharp knife afterwards. But a few mm of mortar bridging it will not do any harm.
Old slate ones were usually pointed over (even on single skin walls).
Also, the DPM should be layed on an uneven bed of mortar, around 5mm, so above and below is "locked" and cannot slide. DPC should not be placed direct onto bricks with nothing bonding it, and where it could get pierced by a sharp edge (often sharp bits around the holes in perforated bricks)
If you think about it, it is engineering common sense.
Simon.
It's done in different ways, but the NHBC guidance is the same nationally.
B&Q and home extensions are not covered by the NHBC.
The mortar is just a cushion for the DPC and does not lock it in. When brickwork expands it can slide on the DPC which ever method is used.
The DPC is often put directly on the brickwork in the West Country, and although I was taught to bed it in the SE, I have never known any problems using this method. If there was Building Control would not allow it.
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