Installing Cills + Dormers Expanded Metal

yop

Lads

2 questions please, I have a good idea of what I am doing with both but since I know ye lads have a good working knowledge of what to do I seek your advice.

Blocks going up next week, I have the cills ordered (the hassle of getting 18" TF cills!!! ) so around the windows I have fixed the DPC. Now what else have I to do before the cills go in, I read some where about a mastic that has to be put on the cill lip, but cannot remember all details. Is there insulation or anything else I should do???

Dormer - Will be making the gable ends tonite, not 100% sure how to do them but I will study them and figure them out, cannot be too hard...?

Expanded metal, this has to go onto the side of the dormer before it is plastered. Now I presume this goes on without any lapping of the metal and is nailed onto the dormer,
there are "2 sides" to the expanded metal, which side faces in?
How far up the dormer does it go, the whole way to the top so that the plaster can plaster all the way to the top of the dormer (sides) or just to the level where the lathe I will nail on for the soffit is?

What are the steps, is it attach the lathe for the soffit, then attach the expanded metal, then get it plastered and attach the bead for the soffit?
Or is there another way?

Or have it all ars* about face!!

cheers

patrido

i'm sure you'll get more informed answers from more experienced members, but here's what i'm doing...

we screwed on a layer of marine ply outside the studding and on the gable. then we did all the lead work. *evil* lead.

next i'm putting on a layer of mineral felt (also evil) and then i'm nailing the expanding metal outside that. using a con saw, i cut the face about 1 inch thick, off lots of hallmark stone, and i'm going to use these for the sides of the dormers. i'll plaster the expanding metal first, then use quick drying cement to "tile" the stone on. that's the plan anyhu

if i understand you correctly, i think the way you describe will work fine.
i think u want the expanding metal and the stone to come slightly above the level of the soffit, so that the soffit comes in to meet the wall... and not have the plaster coming up to meet the soffit. see attached image - don't let kadman see my feeble attempt at drawing

for the soffit on the main part of the roof, i screwed a triangular piece of wood to the underside of the rafter to attach the bead to.


regarding insulation and the cills- not sure how everything works on a tf, but on a "normal" house, when filling in behind the cills with mortar, you put a layer of insulation (i used 25mm) along the back of the cill, up against the DPC. did the same when closing the cavity.

rooferPete

Hi Gents,

There are a lot of questions in the above posts and even though the questions are well described and understandable it would take a lot of bandwidth to go through the details not to worry that I would be typing all night.

Yop,

You need a bedding mastic on top of the cills under each window, I can't recall the type of window you bought but it might serve you well to wrap them in polythene (except the bottom) to keep them clean while the other trades work away.

I am still trying to figure out why you needed cills 18" deep.

Patrido

A rule as old as the plastering trade is the top coat should not be thicker / heavier than the scratch coat, I trust you have found a system to anchor the stone to the timber base ?

.

kadman

Hi Yop,

I would imagine that you received a nailing and erection schedule for your tf kit. Some where in that schedule you may find a procedure that outlines the scope of works associated with the insulation, cavity closers, and fire proof seals. As each tf company may have different instructions regarding " their " procedure in this area, a phonecall to the designer, will result in a fax outlining the route to go. Any deviation from "their " preferred route is probably not a good way to go.

I would have thought that the tf kit came with the dormer panels made .
If not , again a phone call will get you the dormer panel drawings, and you could construct from them. They should also be able to send you sections to get the insulation / seal details.

Good luck guys

kadman

yop

Peter No problem at all

I am putting natural 8" stone on the front and with the 4" solid and 2" cavit I need the 18" cills.

Anchor the stone to the TF, no to be honest.

rooferPete

Hi Yop,

Thanks for the explanation regarding the stone I should have remembered that one, the wall detail is very good in itself, maybe some ties from the 4" to the stone work would keep it all together for you.

My question regarding the anchors was for Patrido, I would be concerned at the weight of the plaster and the stone hanging from the ply.

.

yop

Thanks for that, I have a 4" mesh to hold it all together.

Any suggestions on the dormer, is my setup standard from what u have seen?

Also the gable ends, how are they done exactly?

kadman

I would have thought your tf supplier, supplied all the dormer panels. And all the dimensional locations of the same.

How come you dont have them. Has the roof been installed at this stage, or in what part of the build are you at

kadman

gregos

patrido wrote:

i'll plaster the expanding metal first, then use quick drying cement to "tile" the stone on.

Patrido, this is not a safe plan. You need some system of mechanical fixing to secure the stone to the main structure. You can't just stick it on with mortar: there's a good chance that somebody will be injured or worse in the future if (and when) this goes wrong.

yop

Kadman sorry, bit vague, I meant for the gable ends and expanded metal,

but after today both are now done, the fooking hands are cut off me with that expanded metal sheets, sharpe sh*te so it is!!!

kadman

Hi Yop,

You being the concientious type, I thought you would have had gloves in your safety work wear kit.

No doubt you will have next time

kadman

rooferPete

Hi,

Patrido,

I would take what Gregos posted very seriously

I may be seen as biased against plaster on plywood because I have seen many failures in the system and what should have been easy flashing details made impossible to fit correctly.

Looking at your spec I would ask is the mineral felt old type like used on garden sheds or new modified bitumen ?

Either one has it's faults for this job, the old type will rot behind the plaster, the new type being nominal 5mm thick will make fixing the expanded metal more difficult with large head clout nails.

The scratch coat of plaster is standard, the finish unless mechanically fixed will do one of two things, it will most likely fall off because all timber which is your base moves, if it is possible to bond the stone to second coat it will most likely crack and leak because the finish can't move with the timber.

Yop,

Make sure you fit the cover flashing with 100 mm height to allow your flashing detail to get enough upstand behind the cover flashing, that means at least 150 mm of lead with an stop bead behind the mesh.

For both dormers I would prefer code 5 lead on Geotex as the waterproofing and finish, my reason is it will allow the timber to move and flex as the seasons dictate.

If lead is not to your liking then you could look at 250 mm x 150 mm clay tiles or natural slates, if you don't like my finishes then at least use a rot proof membrane behind the expanding metal and keep the cover flashing behind the membrane.

.

patrido

Ok, now you guys have got me spooked. But I appreciate finding this out now, and not in the next storm

This wasn't just a hairbrained idea I came up with myself or with the lads in the pub - I was led to believe (experienced source, etc) that this was the standard method of putting stone on the side of dormers.

rooferPete wrote:

it will most likely crack and leak because the finish can't move with the timber.

I can dig that, but if so, should the very same not also be true of a plastered finish? And a plastered finish is very common on dormers.

Is this why PVC cladding is so popular - I always considered that it was the cheaper option. What are the other alternatives - wood?

kadman

Hi Patrido,

What thickness is the stone you are using, there may be some confusion as to decorative facing materials, or solid building stone.

kadman

patrido

it's about 15mm. I got my brother in law to cut the front off the stone and the rest was thrown away (or aside). It is incredibly light - which was why I used the tile analogy.

rooferPete

Hi Patrido,

Quote

I may be seen as biased against plaster on plywood because I have seen many failures in the system and what should have been easy flashing details made impossible to fit correctly.

PVC is the cheap and cheerful method that looks good for a few years, refurb of PVC systems is a business for the future if anyone is interested.

Slate or tiles are fixed to the dormer as is good quality timber, the only disadvantage with timber is the maintenance.

There is what appears to be a stone finish on the market that is fitted very similar to the way you described, as I understand it the system is lighter than real stone and designed to be used as you described.

.

yop

Is that the Prefabricated stone you are on about Pete? The like of Fernhill stone do it?

rooferPete

Hi Yop,

Yes Fernhill is what I had in mind for the fixing detail, however I would be hesitant about giving an opinion as to recommending one over another.

The less weight you have pulling on the expanding metal the better the plaster is never fixed to the structure, it's only as good as the fixing of the metal.

.

kadman

Hi Rooferpete,

How about a cleader angle in place of the stop bead.

http://eusteel.com/EUP/CleaderAngles.html

This could be screwed through the plywood with 5x70 screws into the studwork. This should give a good strong fixing . The mesh and scratch coat would also then be supported by cleader angle, as well as the stone facing tiles. As the rails would be galvanised, there should be good protection against rust.

It would be a significant improvement, compared to no support rail.

Just a thought,

kadman