Supporting window bay with Acro's

[frank999]

I am soon to replace 2 large 7 facet bay windows, the ground floor one though has me concerned, it has 1138mm projection, 3000mm opening, 1750mm height.

I have calculated the ground floor bay has a combined load of 3 tonne sitting on this old wooden frame, maybe some of this load is supported by the floor above.

The barrel is single leaf brick, with timbers running vertically between the upper and lower floor window frame transoms.

To get the one piece welded uPVC sill in place and start assembling the window - all the old load bearing frames will need to come out - which is a scary prospect with 3 tonne above my head.
Attached is an image of acro's being used to support a bay wall.
I am interested to know how I would support this, in my mind 5 acro's used around the base perimeter of the brick bay wall would suffice, at a slight angle it keeps the bay pushed against the return wall - and props it up at the same time.

I also see the first floor Joists act as a sort of cantilever - running the length of the bedroom, and project out over a steel beam (which spans the opening) - these joists finish inside the single leaf brick wall - with brick laid on top and around them - could I assume that some load is taken by these floor joists ?

 

[tony1851]

Where do you get 3 tonnes from!?

 

[frank999]

Hi Tony, thanks ...
OK:
Basic calculations and material weights* derived from page 3 if this document ...
http://iframesub.discoverproductivity.co.uk/bay-poles.pdf

Gabled tiled roof (Redland 49's) area 4.96 sq mt x 250kg* = 1240kg
First floor windows: glass 83kg, uPVC frames 50kg = 133*kg
Bay Single leaf brick wall area: 5.96 x 225kg* = 1281kg
First Floor: area 3.075 x 220kg* = 676kg

Total loading 3330kg (3 tonne).

This does not take account of any snow, or imposed/live floor loadings.

But I'm no structural engineer, but figures seem roughly right, unless of course the material weights given in the Nicholls and Cooke guidance are off.

 

[frank999]

forgot also ...there's a single leaf brick infill at the gable end ... area 1.18 sq mt x 225kg = 265kg

So I make it 3595kg.

(I am right in thinking there are 1000kgs to the 'tonne' ??)

 

[tony1851]

'evening Frank;

just looking at back-of-envelope figures:

Your tiles won't be anywhere near 250kg/m2, more like 50, + say 10 for the rafters, felt, battens, say 60kg/m2 max.
Your single-skin brickwork, plastered both sides, is about right.
The floor area supported by the frame will be < 3 sq.m, and typical floor dead load is around 50kg/m2.
Dunno about the glazing and frame but looks in the right order.

Your live loads would be around 60kg/m2 snow load on the roof (measured horizontally)
and floor live load would be about 150 kg/m2.

 

[RonnyRaygun]

'evening Frank;

just looking at back-of-envelope figures:

Your tiles won't be anywhere near 250kg/m2, more like 50, + say 10 for the rafters, felt, battens, say 60kg/m2 max.
Your single-skin brickwork, plastered both sides, is about right.
The floor area supported by the frame will be < 3 sq.m, and typical floor dead load is around 50kg/m2.
Dunno about the glazing and frame but looks in the right order.

Your live loads would be around 60kg/m2 snow load on the roof (measured horizontally)
and floor live load would be about 150 kg/m2.

Tony would you agree that live loads aren't really an issue for the purpose of propping? As long as it doesn't snow heavily while the props are in place, a nominal load for a couple of people and a bit of furniture in the bedroom is all that's required - should be a lot less than 150kg/m2.

 

[tony1851]

'evening Frank;

just looking at back-of-envelope figures:

Your tiles won't be anywhere near 250kg/m2, more like 50, + say 10 for the rafters, felt, battens, say 60kg/m2 max.
Your single-skin brickwork, plastered both sides, is about right.
The floor area supported by the frame will be < 3 sq.m, and typical floor dead load is around 50kg/m2.
Dunno about the glazing and frame but looks in the right order.

Your live loads would be around 60kg/m2 snow load on the roof (measured horizontally)
and floor live load would be about 150 kg/m2.

Tony would you agree that live loads aren't really an issue for the purpose of propping? As long as it doesn't snow heavily while the props are in place, a nominal load for a couple of people and a bit of furniture in the bedroom is all that's required - should be a lot less than 150kg/m2.

Yes, agreed; I was just musing, really!

 

[frank999]

Thanks, Ok, reworked those figures, comes to 2724kg, with snow and an imposed load of 100kg (not relevant for propping - but I need to know loading for Bay Poles, which is another question - see below). Not included any wind loads.

CADs of proposed Acrow propping First floor joist positions/supports, I will prop against existing headers - does that look sufficient and stable ?

I also trying to confirm if the 'default' Bay Poles being spec'd by the fabricators are actually man enough for the job, the 'baypole loadings.pdf' shows a load bearing capacity of 0.8 tonne for the 2184 per pole @ 1750mm height, so I have 6 poles in the new window = 4.8 tonne load capacity, and a 'live/imposed' loading of 2724kg.

I am aware their could be greater loading on the two outer poles, a load being carried down from the roof through frame transoms and barrel wall timbers. See the 'Bay Window Structure TOP.jpg' - which shows:
... the gable roof rafters rest each side on a 8x2 plate/joist - (these in turn rest on the outer parts of the first floor Frame Headers), they project forward and frame the spandrel, with another 8x2 timber nailed across the ends - acting as the gable wall base, bricks for the gable end are laid on this hidden facia timber. 4x2 'ceiling' rafters are nailed at 360 centres between the gable 'plates', and rest directly on the frame headers - so they must at least spread some of the load.

 

[derek777]

Hello Frank, those are a nice set of drawings. Just wondering: what software are using ?

 

[CJRatch]

Hello Frank, those are a nice set of drawings. Just wondering: what software are using ?

Looks like google sketch up. Frank appears to be good at it.

 

[frank999]

Yes Google sketchup - relatively simple to do what you want it to do - use free renderers like 'Twilight' to make drawings look pretty if you want.

Tips for using ...
1) Always start by drawing loose geometry on 'Layer 0' (default layer), group items, and only then move them to another layer you have created:
https://blog.sketchup.com/article/sketchup-layers-part-one-sacred-layer0
2) group everything as soon as you create them, otherwise you can't isolate things to amend them later, when grouped - it helps making selections of complete items, and stops parts of your drawing becoming split across several layers
3) put items on appropriate layers
4) make sure 'front' is the front of what ever you are drawing
5) Change inches to mm: Window >Model Info> Units
6) Create 'Scenes' for each view, and update regularly
7) play around with View 'FaceStyle', wireframe, with 'Parallel Projection' is handy for more technical drawings.
8) make sure you have the 'large tool set' displaying, use the 'Dimensions' tool when communicating sizes to people.
9) Use guides to help draw objects - but make sure when pulling them out from existing geometry that they are in square with the xyz, its easy to draw stuff that is just a fraction of a degree out - go off on those and you will end up with all sorts of problems - keep it square !
10) Either export your drawing as 2d JPEG, or Print to a PDF (more accurate)
11) Don't go overboard on detail, if you dont need to, do you need pretty looking door handles ?? who will see such detail anyway.

I drew the whole house with Sketchup, prior to putting a loft extension on the property, helped with the construction no end - and being able to spec and order things over the phone - can't see why you couldn't use it to submit plans to your local council using it, I may be grasping that nettle some time soon, especially after the last two 'architects' lack of caring and failure to deliver.

Windows !!! We had the upper bay in and out 3 times, combination of supplier not providing the right sized poles, capstans and jacks on time, no proper cleaning, cills that were 100mm out - in fact 7 Day Windows branch I dealt with didn't seem to know one end of there a**e from the other, along with a window fitting specialist who turned out to be nothing of the sort, despite turning up in a van with his trade name plastered all over it ... 'S**t Fit Windows'.

The barrel shifted forward a fair amount (5-10mm) when we ripped out the downstairs windows, in future we will use more than just two vertical Acro's inside, and do what I proposed in my Sketchup drawings - with Acro's at an angle outside - to try impede any movement of the barrel away from the building. Will also not let any monkeys loose with a club hammer - knocking frames outwards - I'm sure that contributed to the movement.

Just as a precaution and to stop any further movement, or movement due to seasons (and spoiling the interior finishes) we M10 rodded and resined into the barrel from the return wall.

Both bays been in 6 months now and no movement at all, and had a load of snow, so glad I swapped the poles over, if I'd listened to the '7 Day' local branch - who insisted the lighter grade ali pole would be 'fine', the brick barrel, the roof gable - and probably the rest of it might have all ended up in my front garden one snowy day last Feb.
Speak to Duraflex technical if you want a proper opinion, the local 7 day branch didn't seem to have a clue, and even though the area reps seemed concerned with customer relations, all my complaints were never chased up and dealt with at all.
I was left with a great pile of ali tube, sleeves, 2 sets of wrongly made cills, boxes and boxes of expensive Jacks and fittings, and a huge amount of plastic profile.
I've been in business for 30 years, and never come across such incompetence.

If you DIY such a difficult thing as a 7 facet bay window - make sure your window supplier knows what he's talking about.

 

[garyo]

- can't see why you couldn't use it to submit plans to your local council using

That's what I did but found I had to splash out on 'layout' so that i didn't go too insane. I did the regs full-plans submission too and it's surprising how valuable it is to think through everything in minute detail

 

[frank999]

Yes concur with the 'insanity' comment - can be a lot of fiddle diddle if your doing big stuff, you will need layout to 'layout' all your different drawings, the SU files will update automatically in Layout if you amend them though, which is good.

Agree that drawing it yourself (especially if you are also building it yourself) helps greatly in knowing what connects to what and in what manner, I am considering another extension, and using these people for the comments/notes:
https://www.buildingregs4plans.co.uk/index.php
Obviously any structural work requires a qualified structural engineer to supply calcs and drawings.
I have also used a private BC company who helped spec. things - as long as you show your diligent and competent, they are happy to work with you, what they don't like (and won't approve) are people who want to cut corners, have no desire to work to the required standards, are incompetent or negligent. The BC co. had a few tales to tell.