Slate pinning of replaced bricks

[booky1]

I'm building a pitched roofed extension that will abut the gable wall of the existing house. I'll need to fit a cavity tray into the existing wall above where the new roof will meet it.

I'd considered dismantling the outer leaf of the existing wall to below the new roof level and then rebuilding with the cavity trays in place but this is a lot of work (and I'm probably the worlds slowest at laying bricks so the inner leaf would be exposed to the elements for quite a long period).

I'm favouring the method outlined in the booklet produced by Cavity Trays Limited of Yeovil i.e. remove three bricks, fit cavity tray section, replace two of the bricks, remove the next two bricks --- etc, etc.

I'm happy with this except that, in the booklet, it says that when the bricks are replaced they should be 'slate pinned' to ensure the wall above remains secure and fully supported. Can anyone please tell me what 'slate pinning' entails and whether this method of instaling the new cavity trays is considered to be good practice - I don't want to compromise the structural integrity of the existing house. Thanks very much.

 

[noseall]

slate pinning is using natural slate as a driven-in packer or support for the masonry above.

this method guarantees the bricks above your replaced ones are supported rather than relying upon pushed-in mortar.

 

[booky1]

Thanks a lot for the quick response. Is the slate pushed in immediately after the brick has been replaced or should I let the mortar 'firm up a bit' first. Also, where exactly should the slate be installed within the mortar joint - top, bottom or middle?

 

[noseall]

let the muck go off. if they are frog bricks then fit the slate near the perp, otherwise central to the brick above. in other words central to the brick above in both cases.

 

[booky1]

Thanks again for the clarification. I've got it now (I think?) except for one thing (sorry for being dense) --- I'd always assumed the slate used would be a relatively thin section that would be forced in between the brick and the new mortar joint somehow but if I understand you correctly I now think I was wrong.

Are you saying that the brick is bedded on mortar as normal but the joint between the top of the new brick and the wall above is left empty then, after the bottom mortar bed has gone off a full depth (10mm) section of slate is wedged firmly into the open joint, then presumably any gaps between the slate pins are pointed up as normal.

Have I actually got it now?

 

[noseall]

yes. locate the slate so that it is recessed from the front arris of the brick as this will allow for a bit of pointing.

the slate packers do not need to occupy the entire width of the replacement course. intermittent packers will suffice provided you do your best to fill the remainder with mortar.

 

[booky1]

That's great - thanks a lot.

 

[kaja]

This is exactly what I need to do myself, but one burning question is where you actually source 'Slate Pins' ?

Also, are these pins actually made of Slate?

Any & all help appreciated.

 

[^woody^]

There are no slate pins. There is slate, and there is pinning, and mix the two togther to form slate pins!

Use natural slate and not artificial too!

If anyones doing this type of work often, then I recommend getting hold of this pointing gun from www.pointmaster.co.uk. I use one now, and the nosle gets right to the back of the joint and its filled soild in about 2 seconds. No faffing with the trowel and trying to fill frogs and holes

 

[noseall]

will this pointing device deal with ANY type of mortar mix, or does the mix need to particularly 'fatty'?

 

[kaja]

There are no slate pins. There is slate, and there is pinning, and mix the two togther to form slate pins!

Use natural slate and not artificial too!

Thank you Woody .. I was starting to suspect this

 

[^woody^]

Yes it needs to be fatty with added soap or lime. Its the water separation that is the problem

But I've tried a few now, and this one works well - I thinks its due to the wide nosle.

Using it for repointing takes some mastering - OK for perp joints, but moving it along bed joints and pushing at the same time takes some co-ordination

But for brick replacement or cracks and packing etc, its great. Just remember to keep the inside clean

 

[gangman]

Personally I never use slate for packing. I prefer to use motar.

I've come across loads of steels, lintols, brickwork etc. packed with slate and you can pull it out easily, you only need a slight movement in the structure and things can loosen up. I know this is not always the case but I do a lot of strucural work and in my opinion a solid packing of mortar is the best way, you don't get any voids as you can with slate.

To the OP as an alternative to the plastic trays you could make your own out of lead, this way you can sometimes take out more brickwork in one go. The last time I done this I was able to take out 5 or 6 bricks at a time.

Which ever type of tray used, when laying the bricks, fill any frogs first and after you've placed the brick use a pointing trowel and a small piece of flat wood and get some dryish mortar into the bed. Don't try and force to much in but try and fill just along the back edge of the brick about an inch, getting your hand into the cavity to stop the muck falling through helps you to compact the mortar better. Do this on each brick, one at a time.

When all your bricks are in place leave them until the mortar starts going off then you can finish packing the bed. Get some dryish muck on your trowel and using the piece of wood push it into the bed. Be a bit gentle pushing against the muck already in the bed, try not to push it out. Get your hand in the cavity again and where you can reach hold the muck in place as you compact against it. When you have a bit of depth you'll find you can use more pressure when forcing the muck in. Keep building up the muck along all the bricks until it's completely filled, don't leave any voids at all, water can fill these and cause you problems.

You need to use dry muck for the packing as there will be less shrinkage. What I do is make some mortar in advance and let it dry out or a quicker method is to put mortar on some dry bricks or blocks and they start sucking the water out of the mix. You can get additives to stop shrinkage but I find that you can make a better job of packing with dryish mortar, it compacts better than a mix that is a bit wet.

When the packing is done remember to clean the cavity out. You can use your piece of wood to scrape the tray or get some water in there to wash it out. If you use water make sure the bed's quite dry and don't let it run too long or you'll start washing the bed out.

I've done a lot of this type of work, and over the years I think for me this is the best way to do it. Others do it a different way, that's ok, for you it's good to see different methods and then you can choose which will work best for you.