A couple of building/painting questions

[Student]

A couple of questions for all those knowledgeable folk out there.

Firstly, over our side door, there is a small porch. Between the lintel and the tile hanging, there is some lead flashing which was held in place by some mastic compound presumably to allow for expansion and contraction of the metal. This has now deteriorated causing the flashing to slip and I have already had to push it back into position. At the same time, I removed most of the old mastic. The attached pictures show the problem.

The question is, should I try putting it back into position and use an exterior frame sealant to fill the gap and hold it in place or use cement pointing.

The second question relates to multi-purpose paints. I have to paint our up-and-over metal garage door plus touch up the paintwork on some balcony railings; both currently have gloss paint finishes. I’ve read recommendations for Bedec MSP and Zinsser Allcoat Exterior at various times and both seem to get reasonable reviews. I’m inclined to go for the Bedec as their gloss seems to be more widely available, e.g. through ToolStation, than the Zinsser. However, I’d welcome thoughts from our fraternity.

 

[MikeG.]

The lead is an easy fix. Firstly, take out all of the pointing in that bed of mortar holding it in place and straight the flashing up. Mortar and lead shouldn't be in contact. Then, you need to get some scraps of sheet lead, just a few square inches. Cut these into strips about an inch wide (you can use a Stanley knife if you don't have tin snips), and fold them over, and maybe over again, then squish them down a bit such that they are a tight fit into the mortar bed above the flashing. You then tap them carefully into position above the flashing, using a bolster (cold chisel) or even a wooden wedge to do the final packing in, such that they are at least 5 or 6mm back from the face of the bricks. This jams the lead flashing firmly in place. I would have thought that 3 such lead wedges would be plenty for that little bit of flashing. Now you use the appropriate low modulus silicon to fill in the mortar bed.

Zinsser is a hard paint, Bedec is flexible. I would expect the Bedec to cope better with seasonal movement than Zinsser. Having said that, neither of them will work terribly well if going over old paint, because they are adhering only to the existing paint, and not to the underlying door. When that old paint gives up, it will take the new with it.

 

[Mike Jordan]

The lead flashing is normally inserted into the mortar joint about 25 /30 mm and secured with wedges of lead. The wedges are made by folding up off cuts of lead sheet to make the required thickness of material to jam tight when driven into the joint with a blunt drift. They are driven below the face of the bricks and the joint is the pointed with mortar to match the rest of the wall. It's normal to use the joint one course above the tiles.
Mike.

 

[Student]

Thanks to both Mikes for their prompt response.

Noted about the paint but I will probably strip most of the old stuff off before I recoat. Previous attempts using gloss paint have never been terribly successful so I'll give Bedec a go. At least I can get a couple of coats on in a day.

The flashing is more of a problem. I don't have any offcuts of lead and spending £40 plus just to get a few 4 or 5 square inches to make wedges is a non-starter. Is there an alternative? As the lead flashing is soft, would some plastic packers work?

With regard to the pointing, the lead is dressed over a wooden framework which is underneath the brick course and there is no mortar in the gap between the wood and the brick just mastic at the front and a void behind. I notice that Mike G recommends using mastic to fill this gap and Mike J. recommends using matching mortar. If I was to use mastic, I have no idea what a low modulus silicon is but assume that it's lead flashing sealant.

 

[Noel]

Low modulus ( Neutral) is just more elastic and more sticky than the regular stuff and should last longer.
Ref the lead if you've no spare lead find some flat pebbles (the size you'd use for skimming would be ideal) and knock them in with a drift or chisel or whatever is handy. Then some mortar/mastic to make good.

 

[Ttrees]

I done something similar before with copper as I had only a tiny bit of lead on hand, you don't need as much lead as you think.
I eventually found the procedure on youtube and it is called a reglet
There are a few videos on folks doing work them on parapet walls and chimneys online.

MikeG is there a quick explanation on why mortar should not be in contact with the lead?
Thanks
Tom

 

[MikeG.]

.....I notice that Mike G recommends using mastic to fill this gap and Mike J. recommends using matching mortar. If I was to use mastic, I have no idea what a low modulus silicon is but assume that it's lead flashing sealant.

I'm afraid I can pull rank here, as an architect (sorry Mike J). I work to the industry standard "The Calder Guide to Good Leadwork", which says (Page 12) "Lead is not a satisfactory long term pointing".

 

[MikeG.]

........MikeG is there a quick explanation on why mortar should not be in contact with the lead?

Yes, it's simply that it doesn't adhere to it, so there is always a horizontal gap into which water will go. When water freezes it expands, so the gap is forced wider and wider, either by pushing the lead out, or by spalling the brickwork. This damp gap often fills with moss.

 

[MikeG.]

.......Ref the lead if you've no spare lead find some flat pebbles (the size you'd use for skimming would be ideal) and knock them in with a drift or chisel or whatever is handy. Then some mortar/mastic to make good.

This will be OK if you are careful, but has the potential to push a hole through the lead if the gap is too tight. As an alternative, buy yourself a rubber eraser, and cut that into wedges.

 

[Student]

Thanks Mike. Off to Toolstation tomorrow morning for the Bedec and low modulus silicone plus a trip to W H Smiths if I can't find enough of the right size of rubber erasers at home.

 

[RogerS]

If it's not too late, why not use the proper lead sealant designed for the job? Something like LeadMate from Everbuild?

 

[Woody2Shoes]

Hi -

a good alternative to lead rolls/wedges for fixing lead flashings are these stainless steel fixings if you have a roofers merchant or good builders merchant near you, these are not expensive, easy and effective (there's also a plastic equivalent which works but is more fiddly):

https://www.britishlead.co.uk/hall-clips

You can get low-modulus silicone (silicon is something very different!) in grey specifically for leadwork.

Aside from the thermal movement problem - mortar having a much smaller coefficient of thermal expansion than lead means it's best to allow them to move independently of each other - I've always thought that a key reason for keeping lead and mortar separate is that mortar is alkaline and will tend to stain the lead (painting the bits of the lead which would otherwise be in contact with mortar using a couple of coats of bituminous paint would protect it from this effect, and help to prevent/minimise mchanical bonding I guess). I suspect that in the days before silicone, mortar was used (with or without any bitumen-type paint).

If you use any new lead, or spoil the patina on the existing, it's well worth spending a bit extra on lead patination oil - I suspect that linseed oil would probably work as an alternative. https://www.wickes.co.uk/Calder-Patinat ... l/p/240295

Cheers, W2S

 

[Bm101]

Jumping in quickly.... Sorry... is there a recommended brand(s) for low movement silicone? Any tried and tested names? Storing facts for a new oak porch I want to be after doing next year.

 

[Woody2Shoes]

Jumping in quickly.... Sorry... is there a recommended brand(s) for low movement silicone? Any tried and tested names? Storing facts for a new oak porch I want to be after doing next year.

They're all much of a muchness - Everbuild products are good value and seem to be reliable (I think they're also made in the UK hooray!). The vitally important thing is to read the product data sheet to make absolutely sure it's the right stuff for your particular application (materials/exposure/paintable/etc.). https://www.idealsealants.com/a-brief-g ... alants-i18

https://www.everbuild.co.uk/product-cat ... -sealants/
https://www.everbuild.co.uk/product/lead-mate-sealant/

Cheers, W2S

PS don't forget, Low Modulus = less rigid, High Modulus = more rigid -

 

[Bm101]

Many thanks Woody.

 

[Woody2Shoes]

Item ten is a good example of the staining effect of mortar on lead, and how to avoid it - cheers, W2S

https://www.ribaj.com/products/the-top- ... lead-sheet

 

[Student]

First of all, many thanks to those who have tried to help me.

Over the weekend, I attempted to sort out the flashing without success. This is a sketch of what I am faced with.

As can be seen, the front of the joint is set back about 2 cms from the face of the brickwork. The joint itself, into which the lead is supposed to fix, is between 5 and 6 mms thick and about 2 cms deep. The lead flashing is 3.5 cms thick which makes it a tight fit into the joint and gives very little room to insert the flashing and then to use a wedge. There was one bit of good news in that my next door neighbour had a small offcut of lead to make wedges but more of this later.

Trying to slot the flashing into the joint was a nightmare as, being “second hand”, the edges were no longer perfectly flat and I eventually gave up. It seems to me that I need to widen the thickness of the joint to, say, 10mm and then use a 6mm wedge, possibly using a hall clip as previously suggested rather than a lead wedge (don’t forget that I am an amateur at this).

When it comes to filling the joint with silicone, I bought some Everbuild 450 Builders Slicone

https://www.everbuild.co.uk/product/450 ... -silicone/

which I thought might do the job. Do I really need Lead Mate Sealant

https://www.everbuild.co.uk/product/lead-mate-sealant/

If so, I’ll go back to ToolStation and exchange one for the other.

 

[Woody2Shoes]

Hi - from reading the data sheet the stuff you've got looks fairly much the same stuff as their "lead mate" sealant, so would probably work just as well (low modulus, neutral cure being the key words).

What colour is the stuff you've got? I assume white. That in itself would be enough to make me want to swap it for the "proper" stuff which is coloured to match lead.

I've re-read your latest post and I think your plan is broadly correct. I think you'll need to remove the flashing to get a chisel/ankle-grinder in to widen the slot - beware of possible white lead oxide dust underneath. I think you'd do well to use patination oil (or at a pinch, linseed oil) on the flashing.

Cheers, W2S

 

[MikeG.]

........Trying to slot the flashing into the joint was a nightmare as, being “second hand”, the edges were no longer perfectly flat.........

Take the lead out altogether, and using an off-cut of wood (a bit of 4x2 about 6 or 9 inches long would be perfect), gently beat the crinkly edge of the lead flat. It will need to be on a wood surface when you do this. Beating lead is easy, and you should also be able to bend it easily to follow the profile of that step at the top of the tiles, too. If you can't, fix a batten in there to pack out the void. The whole point of lead is that it is soft and easy to work.

Please remember to wash your hands thoroughly afterwards, and particularly before you eat anything.

 

[Student]

Thanks again Woody and Mike.

I did, in fact, take out the lead which was how I managed to determine the depth and width of the groove and also the thickness of the lead.

I did also beat the lead flat using a piece of wood underneath and a wooden mallet to hit it with. This straightened it out but I found it very difficult to get it absolutely flat i.e. within a mm or so along the metre or so length. The problem is that, when picking it up, it tends to bend. I have tried using a long piece of wood to support it when trying to push it into the groove but it's difficult to do this one handed. Hopefully, once I have widened the groove, the flashing will slide in more easily.

One final thing: my design guru didn't like the idea of brown silicone so it was back to ToolStation to exchange it for grey Lead Mate.