Wall ties and d.p.c. - please help !

[P.J.]

Hi All,

I'm installing a catnic style lintel over a new door opening in the gable end of my house and I'd be grateful for some help:

1. I need to fit a d.p.c. over the lintel. What happens with the dpc at each end of the lintel ? Do I just cut it flush with the end or run it into the brickwork either side by 100mm or cut it short or something else ?
2. Some of the wall ties will be lost when I cut the new door opening. Do these need to be replaced, say, either side of the new door opening, level with the original tie positons ?
3. Lastly, what do I do to the exposed cavity around the new opening ? Is there an insulated piece of trim I can push in and render straight over for make the reveals ?
All advice very gratefully received.

Thanks,
P.J.

 

[Thermo]

When you say a catnic style, do you mean a powder coated metal jobbie that is high at the back and slopes down to the front?

 

[P.J.]

Yes, that's the kiddie. It's sheet steel with a top-hat in the middle to carry the polystyrene insulation and give a run-off.

Regards,

P.J.

 

[JerryD]

You use 'cavity closers'. Get these from a good builders merchants. They come in various widths to suit different cavities, usual sizes are 50mm, 60mm, 75mm and 100mm.

Most common size for houses over 5 years old is 50mm or 60mm. Just measure your cavity at its narrowest point and that's the size you need.

These come 2.4 metres long and some are 3 metres long usually so you'll need two.

If they have a choice, get the double flanged type (as in piccy below) rather than the single flanged. Double flanged sit over both the blockwork and the brickwork whereas single flanged only sit over the blockwork so are more difficult to get rigid.

 

[P.J.]

Thanks JerryD for the advice - very helpful.

Can you tell me if they should be bonded in place or screwed through the flange into either leaf please ?

Also, anyone have any ideas on what I should do with the dpc and the wall ties ?

Thanks,

P.J.

 

[Thermo]

if my memory serves me correct the way that the catnic style lintel is made means it acts as its own cavity tray, you just have to ensure you put some weep holes above it. Have a look at the catnic site they are normally very informative.

I wouldnt worry too much about the stability that hasd resulted from the walls removal. The surrounding wall ties will be at the correct spacings to give it the strength it needs

Thermo

 

[JerryD]

If you can get a mechanical fix into the blockwork then do so (i.e. galvanised clout nails) but often this is not possible if the blocks are not suitable for nailing into.

What we have to do sometimes is glue the cavity closers into position using Gripfill or the equivalent. (NOT SILICONE) Run a bead of the adhesive on the wall on both the blocks and the bricks (to glue both flanges) and quickly stick the closer into place before the adhesive skins over. Rub the closer around to get the adhesive well spread onto the surface of the adhering faces.

Plenty of adhesive will ooze out, just spread this over the join too (it all helps). The closers will now need bracing into place using anything you have to hand (lengths of batten etc), in other words wedge timbers across the opening from closer to closer to push the closers tight to the adhesive.

Leave this braced up for a minimum of 12 hours. Remove the bracing and those closers will be solid as a rock!

As has been said by others, the lintel has its own built in cavity tray.

As for the wall ties, really there should be a wall tie every three course of bwk at the openings (about 150mm in from the opening, on both sides) but you can do more damage trying to achieve this. I would not be too concerned about adding any further wall ties.

 

[P.J.]

Thanks alot for the advice.
The catnic site shows the lintel being used with a dpc. It is fitted into the inner block leaf, at the course above where the lintel sits, and runs over the lintel to the outer leaf and out between the lintel and the brick course that sits on it. Not sure why, and it says the dpc is only required in geographical areas of heavy weathering, one of which I live in ! So I think I should fit one, just to be on the safe side. It doesn't show how to end the dpc at each end of the lintel. Any suggestions ?
Thanks again,
P.J.

 

[JerryD]

OK, if you're in an area where the weather will affect the wall then these lintel manufacturers do recommend a dpc tray over the lintel. This is to stop wind driven rain getting onto the lintel within the cavity and dripping off the ends, causing possible dampness within the wall lower down.

So you need to lay a dpc tray over the lintel but turned up each end to stop water running off the ends. The tray is built into the face brickwork with the lintel (tray actually sits on the lintel). Weep-holes are now essential to allow this water to run out through the face brickwork. Propietory weep-hole liners are available from a good merchant.

Why the lintel manufacturers don't supply clip on plastic 'ends' for these lintels I'll never know, much easier imho.

 

[P.J.]

JerryD,

Wise words once again. Of course it has to turn up at each end . And thanks for the advice about the weep hole liners. Think that's my job almost sorted.
Many thanks,
P.J.