Crack in internal masonary

[Ginga]

Hi, Wonder if anyone can please help/advise me? I've removed the blown plaster from one of the bedrooms in our late victorian house. The bedroom is at the front of the house, on the first floor, above the lounge which has a bay window. A wooden joist spans the width of the downstairs bay window at floorboard height in the bedroom. In the middle of the the front bedroom wall the internal wall bricks sit on top of the joist and where there has been slight movement of the joist over the years, 2 cracks have appeared, following the line of the mortar, from each joist end up to the front bedroom window. We are having the walls re-plastered, my question is "What sort of re-enforcement could I put over the cracks ( prior to plastering) to prevent further movement and hence the new plaster finish from cracking"
Thanks a bunch in advance!

 

[Richard C]

Remove the plaster back to the block/brickwork, rake out & fill the crack with mortar mix & then fix Stainless Steel wire reinforcing mesh over the whole area, extending to at least 150mm (more if you can) either side & beyond the crack. Ideally, use a sand/cement render to cover & fill to plaster depth before skimming. I’ve had mostly success using this method where future movement won’t be a problem or is minimal; but there are no guarantees! Alternatively you could dry line with plasterboard & skim the whole wall.

 

[Ginga]

Thansk Ricahrd, that sounds like a plan. Is the Stainless Steel Wire mesh a "special" or can I get it from any building suppliers yard? ( We seem to have loads round here! )
Cheers

 

[Richard C]

Thansk Ricahrd, that sounds like a plan. Is the Stainless Steel Wire mesh a "special" or can I get it from any building suppliers yard? ( We seem to have loads round here! )
Cheers

You should be able to get it from almost any BSM (Y!) but a B&Q trade outlet will have it. I tend get the majority of my general supplies from a trade B&Q as, for a surprisingly large number of things, they are actually far cheaper than the rip off prices the 3 national BSM supplies outlets are asking in my neck of the woods; & that’s with a supposedly 40-60% discount!

 

[Ginga]

B and Q it is then!.
Thanks again

 

[Ginga]

Hi, primed the masonary around the cracks with 1 in 5 pva mix and then pinned the expamet (EML) onto the wall with galvanised staples hammered into the old lime mortar joints and bricks ( they're quite soft ). Got a bag of mortar mix from B and Q, mixed it up as per instructions. the bag said use 3 lires of water, I found that I had to use 3.5 to get the mix wet enough(still seemed a little dry to me though ). Sparayed the wall with water and applied the mortar mix to the metal lath, pushing it on firmlywith a plasterers trowel with two hands. this was 3 days ago, its about 6mm thick, up to 12mm in some areas. The render seems ok mostly but a bit crumbly.
However, in some places it sounded "hollow". A light tap with a hammer and the hollow areas came away!. Did I make the mix too wet, too dry or is a ready made mortar mix a pile of "cr*p". I'm disappointed as I thought I'd done all the prep quite well.
I'm wondering what to do with now with the areas that fell away, wire brush the metal lath in the affected areas and reapply with a new mix ( not a pre bagged mortar mix ) Any help greatly appreciated. Ginga ( soon to be bald - not sure whats worse!? )

 

[Richard C]

Did I make the mix too wet, too dry or is a ready made mortar mix a pile of "cr*p". I'm disappointed as I thought I'd done all the prep quite well.
I'm wondering what to do with now with the areas that fell away, wire brush the metal lath in the affected areas and reapply with a new mix ( not a pre bagged mortar mix ) Any help greatly appreciated. Ginga ( soon to be bald - not sure whats worse!? )

I’ve never had similar problems but then I’ve never use used bagged redimix; did you PVA again immedietly before laying it on? If it’s crumbly it’s either too wet or not enough cement in the mix; if it’s hollow when set, the water has been sucked out too quickly & it’s not bonded. Render can be more difficult to apply but it should stuck like siht to a blanket & be strong enough to bind the block work & mesh together. Personally, I would not be happy with any of it & would rake it all out & start again; I use a 6:1 mix but I’m no render expert!

 

[Ginga]

When you say start again, do you mean remove the metal lath as well or just rake out with wire brush? ( I bought two pieces ). Do you think a 1 in 3 PVA "bonding" coat is required before the render Ricahrd?

Cheers

 

[Richard C]

The mesh will probably fall off anyway so just brush it off & re-fix it; & yes with the PVA.