Roof construction help

[PeterW]

11 minutes ago, Vijay said:

Carrier system? I was advised I only need to bond them on.

 

Ok ... so how will you keep them perfectly spaced and level..?? Most systems use a carrier board that you bond the slips to, or sometimes are in preformed panels. 

[Vijay]

25 minutes ago, PeterW said:

 

Ok ... so how will you keep them perfectly spaced and level..?? Most systems use a carrier board that you bond the slips to, or sometimes are in preformed panels. 

9/10mm spacers, just like tiling?  https://www.ebay.co.uk/itm/Wall-Floor-Tile-Plastic-Cross-Spacer-10mm-White-100pcs/302138010245

[PeterW]

Errr nope ..!! That’s not how slips work..!! 

 

You need some sort of carrier system - this one is thin EPS but others are metal frames. https://www.eurobrick.co.uk/v-clad

 

 

[scottishjohn]

using tile spacers would be a long winded job --

wouldn,t consider it 

use a carrier system of some make as suggested by @PeterW

lots to choose from 

[PeterW]

One of the oldest suppliers is Wetherbys and their system is designed for EWI and is a steel grid system. Easy to use and strong too. I looked at this for a job in a conservation area and the plan was to use reclaimed bricks cut to slips on an ICF build to meet planning requirements. 

[Vijay]

Why do I have to use a carrier system though, is there any safety reason?

 

I will certainly look into carriers, but when I enquired about them initially (when I first looked at ICF which seems like a VERY long time ago lol) the price was pretty horrific and I would need a hell of a lot of them...................

 

 

43 minutes ago, scottishjohn said:

using tile spacers would be a long winded job --

wouldn,t consider it 

use a carrier system of some make as suggested by @PeterW

lots to choose from 

 

Everything on my build is long winded - just feel for me when I have to point it all up - now that is what I call long winded!!! ?

Edited May 18, 2019 by Vijay

[scottishjohn]

use ready mixed pointing mortar in a gun  -?

if you use tile spacers --if you leave them in won,t be much covering with mortar ,depending on thickness of slip you choose

 

Edited May 18, 2019 by scottishjohn

[PeterW]

6 minutes ago, Vijay said:

will certainly look into carriers, but when I enquired about them initially (when I first looked at ICF which seems like a VERY long time ago lol) the price was pretty horrific and I would need a hell of a lot of them...................

 

 

So for external use, a carrier provides the mechanical means of securing the slips to the walls. Without it, you are expecting the shear strength of EPS and adhesive to hold the slips on. I can’t see any adhesive manufacturer or ICF manufacturer warranting that sort of system as it doesn’t have any mechanical fixing. 

 

In terms of cost, slips are no cheaper than bricks tbh, the difference is the skills to apply and speed of installation hence why you can get them in panels as they are designed to be used on prefab buildings etc and also as retrofit. 

 

I would start by giving Wetherbys a call... 

[Vijay]

27 minutes ago, scottishjohn said:

use ready mixed pointing mortar in a gun  -?

if you use tile spacers --if you leave them in won,t be much covering with mortar ,depending on thickness of slip you choose

 

I would only insert one leg of the spacer, so would just keep pulling them out and re-using

 

22 minutes ago, PeterW said:

 

So for external use, a carrier provides the mechanical means of securing the slips to the walls. Without it, you are expecting the shear strength of EPS and adhesive to hold the slips on. I can’t see any adhesive manufacturer or ICF manufacturer warranting that sort of system as it doesn’t have any mechanical fixing. 

 

In terms of cost, slips are no cheaper than bricks tbh, the difference is the skills to apply and speed of installation hence why you can get them in panels as they are designed to be used on prefab buildings etc and also as retrofit. 

 

I would start by giving Wetherbys a call... 

 

It's xps if that makes any difference. Polarwall didn't have an issue with it and I contacted a fair few cartridge adhesive suppliers and non had an issue. I do get your point of the face of the XPS coming away with the slip and adhesive, but was assure it was fine.

 

I know slips are no cheaper - they're double the price of the brick!! lol I may end up cutting the slips myself from bricks but that's a long way down the line  

 

I have to use an exact brick and only "sort of near matches" come in panels. So brick slip panels are out the window.

 

I'll give them a call on Monday https://www.wbs-ltd.co.uk/

 

[PeterW]

10 minutes ago, Vijay said:

It's xps if that makes any difference. Polarwall didn't have an issue with it and I contacted a fair few cartridge adhesive suppliers and non had an issue.

 

I can guarantee when you have a problem, none of them will admit liability .!!! You are creating a system, and I would even be wary that it meets building regulations as that will not have any type of certification or BBA etc. 

 

11 minutes ago, Vijay said:

may end up cutting the slips myself from bricks but that's a long way down the line

 

I hope you are joking ..??? There are specialist companies who do this - you need big diamond saws that do multiple bricks at a time. You can’t cut 60000 slips on a wet bench.... 

[ProDave]

On 17/05/2019 at 10:56, PeterW said:

Wall plates on an bobtail truss always go under A. 

 

There is only a cold bridge if you don’t insulate the ends. What carrier system are you using for the slips ..? 

Interesting.

 

I was doing a garage not long ago so walls built of single skin 6" blocks, room in roof above like this.  The trusses were only supported at pint B (with triangles built in at that point to give a flat bearing surface) and point A just hung down between the block walls.

 

I guess there is more than 1 way to do things.

 

 

[Vijay]

45 minutes ago, PeterW said:

 

I can guarantee when you have a problem, none of them will admit liability .!!! You are creating a system, and I would even be wary that it meets building regulations as that will not have any type of certification or BBA etc. 

 

 

I hope you are joking ..??? There are specialist companies who do this - you need big diamond saws that do multiple bricks at a time. You can’t cut 60000 slips on a wet bench.... 

 

That's a very good point that has crossed my mind many a time I can assure you. 

 

Not joking at all. It was estimated I needed around 20k brick slips at just over £1 each (going back a few years so probably changed). I could get a brick for less than that. Both were direct from Forterra who make the brick/cut for slip. Then I  buy a machine something like https://www.husqvarnacp.com/uk/machines/masonry-saws/ts-400-f/965148101/ for a grand or so.  I know it will be a long job cutting them, but if it takes me a couple of weeks, that's a saving of around 10k.

 

I contacted various companies to cut slips from bricks, both with saws and even water jet cutting, both were more expensive than buying the slips direct from Forterra.

[Vijay]

42 minutes ago, ProDave said:

Interesting.

 

I was doing a garage not long ago so walls built of single skin 6" blocks, room in roof above like this.  The trusses were only supported at pint B (with triangles built in at that point to give a flat bearing surface) and point A just hung down between the block walls.

 

I guess there is more than 1 way to do things.

 

 

Any idea if the truss supplier were ok with that?

 

[ProDave]

7 minutes ago, Vijay said:

Any idea if the truss supplier were ok with that?

 

I am assuming the truss supplier designed it like that, it was they that fitted the triangles to make a flat bearing point at point B.

[PeterW]

56 minutes ago, ProDave said:

Interesting.

 

I was doing a garage not long ago so walls built of single skin 6" blocks, room in roof above like this.  The trusses were only supported at pint B (with triangles built in at that point to give a flat bearing surface) and point A just hung down between the block walls.

 

I guess there is more than 1 way to do things.

 

 

 

That is for a garage, there would be no design load on the bottom chord. This is for a a room in roof so the bottom chord is load bearing. 

[ProDave]

2 minutes ago, PeterW said:

 

That is for a garage, there would be no design load on the bottom chord. This is for a a room in roof so the bottom chord is load bearing. 

But the garage was designed to have a room above, which is the only reason the walls go higher than the ceiling level. So the bottom chord is taking a load.

 

I can't recall if that bottom chord was really just hanging there, or whether they used joist hangers at the ends (I would have done) for additional support.

 

This is the only time I have seen it done like that and was surprised.

[Vijay]

I emailed a couple of suppliers about supporting this bob tail roof. First said " We can design bobtail trusses with hangers if required" but the other supplier said "Timber hangers would be an option for trusses with light support reactions, however for multiple-ply girders you’re going to run into problems as face-fix timber hangers can only take up to a certain load. I’d recommend terminating the panel for normal wallplate height so the truss can transfer the load straight down through the wall."

 

I think it makes more sense to keep the wall plate lower, then build up the wall once the trusses are in place with ICF, then if it's ok, I will back-fill the ICF inner core with concrete (so the timber trusses are buried in the concrete)

 

 

[PeterW]

So get them to do a more complex inbound stub that supports the rafter and only buries the joist end in the ICF. It would probably mean the bottom chord is a composite or metal web with a block in it to transfer loads but should be doable. 

[Vijay]

so not a good idea to bury timber in concrete then?

[PeterW]

Only the minimum possible. You wouldn’t want to bury the uprights as it would compromise the concrete strength and thickness and you’d end up with lots of disconnected core segments. 

 

Whats the issue with doing it properly and using a wall plate and then cladding the outside of the stub walls ..? Would be easier and less to go wrong. 

[Vijay]

only for the reason I'd have liked to keep as much of the walls as the same ICF buildup

[Vijay]

Does anyone know why suppliers don't seem to do attic trusses with Posi joists for the floors?

 

I'm waiting on the Wolf system suppliers to get back to me as they may be the only ones who do

[Oz07]

4 hours ago, Vijay said:

Does anyone know why suppliers don't seem to do attic trusses with Posi joists for the floors?

 

I'm waiting on the Wolf system suppliers to get back to me as they may be the only ones who do

Connection detail I'd imagine. If you have gables you Could have gantry beam/truss gable to gable within proper attic area then mono trusses off each side of this down to wall plate. With posis for your floor

[Vijay]

Here's a simplified pic of the single storey roof. It joins the house on the right hand side. I do have 2 Dutch gables, so not sure how they would work to support a beam. Also I think the issue would be where the roof joins at an angle (the 30 odd degree one).

 

Who would design a cut roof?

[Oz07]

You're near me aren't you @Vijay? Try Harlows or Donaldsons. They would usually design based on providing the timber. Who's doing your main roof?

Scrap that just seen location as london!

Edited August 4, 2019 by Oz07