The Carport.

[ProDave]

A part of my build that is still awaiting to be built.

 

And a good job as the parameters have changed as I hinted in another thread a few days ago.

 

It now needs to be built a bit higher than originally planned to accommodate the latest addition to the fleet.

 

 

It's almost 3.2 metres to the highest point so we need comfortable clearance under for that.

 

The size remains the same, 6 metres by 6 metres.  The original plan would have been sloping down from the front to the back, but that would make the front insanely high now, so it will now slope from the garage wall down towards the left.

 

It will be roofed with box profile roofing as originally planned.

 

I will sketch a proposed joist plan in due course to bounce ideas around.

 

But one thing that has become obvious, the car port roof where it attaches to the garage is going to be above the MVHR vents.  I am not sure if that is going to pose a problem or not?

[Iceverge]

I would be worried about some future owner running a car in there on a cold morning to warm it up and the fumes getting drawn into the MVHR. 

 

Could a stand alone structure work?  Or you could always extend the MVHR inlets  out to the fresh air above the new roof . 

[ProDave]

I could extend them (externally) one to the front and one to the back so they were not actually under the canopy.

 

The front one visible is the exhaust, the rear one, hidden in this picture is symetrical so the same distance is the inlet.

 

There will be a small gap anyway, to avoid trying to form any sort if flashing from the wall to the roof.

[Russell griffiths]

You will need next to sod all fall if using box profile sheets. 

[Oz07]

Just been in Australia and nowadays for their patios they are using all these insulated roofing sheets. They seem to be able to get massive spans without intermediate joists or purlins. Possibly worth looking into very simple construction. Saying that you do get big snow loading presumably so prob a no go

[JohnMo]

Stick big 500W plus solar panels on the roof? 

[ProDave]

31 minutes ago, JohnMo said:

Stick big 500W plus solar panels on the roof? 

That is the plan, with battery storage as well.

[Russdl]

How about a freestanding carport, half a meter or so away from the house so the MVHR isn't affected. Park the truck the other way round and have a slight fall front to back.

[ProDave]

42 minutes ago, Russdl said:

How about a freestanding carport, half a meter or so away from the house so the MVHR isn't affected. Park the truck the other way round and have a slight fall front to back.

There will likely be a gap but it can't / won't be that much, the supporting poles will be attached to the garage wall for stability.

 

The whole point of buying this particular type of truck is you can wind he legs down and demount the camper unit from the truck, and use the truck on it's own as a normal vehicle.  So parking the other way would mean driving out onto the grass to demount which would not end well in winter when it is wet and soggy.

[ProDave]

First stab at joist plan for the car port roof

 

There will be 6 posts "P" 3 each side, probably 150mm square all supported on post feet. The 3 at the garage ends will also be bracketed to the wall, to locate them, not to take any weight on the garage wall.  The 3 at the left hand free standing end will require some diagonal bracing.

 

Box profile roofing from the garage high end to the free low end.  Probably with a small gap at the garage end to avoid having to flash it to the wall.

 

Total size 6M by 6M.

 

Box profile roof needs supporting on joists running across it, so in this case front to back joists.  Assumed at the moment 600mm centre to centre spacing  they are Joists B in this plan and each need to span 3 metres.  I don't think these are going to be difficult.

 

The problem ones I think will be the 4 "Joists A" that have to span 6 metres and support the smaller joists.  This is the one I need some design input to see if this proposal is viable.  I would rather they were not too deep, say no more than 8" / 200mm.  But I do expect to double or even tripple these, and there is the possibility of a steel plate between them to make it a flitch beam?

 

Ideas please?

 

 

[Iceverge]

Box profile only needs to supported every 1200mm so I don't think you need anywhere near as many "joist B".

 

The 6m span is the tricky part and all the timber going the other direction isn't doing a tremendous amount really. I'm not sure Filch beams are worth the complexity. Steel would prob be easier at that rate. On both these counts I don't like having timber interfacing with steel in an unheated environment ,if it's avoidable, as the condensation that the steel attracts will rot the timber eventually. 

 

 

Finger in the air, farmer "engineering" here...... I'll try to avoid anything bigger than 225*75 as it doubles the price very quickly.

 

 

I would erect 5 x 150*150 posts at 1500mm centres along the low and high side of the carport. Notch the tops of the posts and drop in a single 225*75mm timber running the full length of the carport as an end support beam. Add appropriate diagonal bracing on the low side to stop it wobbling. 

 

Drop 9x 225*75mm rafters on top at 750mm centres and secure them to the end beams with metal straps. Add 225*44mm noggins at 1200mm centres to take the fixings for the metal roofing. 

 

I would put a roofing membrane under the metal roofing too to stop it dripping in winter. 

 

Edited 4 hours ago by Iceverge

[saveasteading]

It's a car port. If it looks OK it is OK.

I'm not doing any calculations , but suggest doubling up the big ones, bolted together. Ie 2 instead of 1.

Once it's built, if it feels OK, that's it, if it doesn't, ask again.

 

Failure would be from snow load, drifting against the wall, so clear it, or stay out.

 

Def diagonals at the beam to post junctions for stiffness. Will look better too.

[ProDave]

Interesting ideas @Iceverge

 

So you are suggesting a 225 by 75 would span 6M if it was not carrying too much load? and suggesting 5 of them.  My design already has 4 of them so not that different.  I would rather not go as many as 5 posts each end perhaps compromise on 4.  I will have to mark it out on the ground to see how it would look in reality and where they would land.

 

Yes I thought the box profile could get away with fewer cross beams.

 

I don't want to stack the cross beams on top of the long beams, that adds to the height which is also very high, I want to drop them between the long beams on joist hangers.

[ProDave]

6 minutes ago, saveasteading said:

It's a car port. If it looks OK it is OK.

I'm not doing any calculations , but suggest doubling up the big ones, bolted together. Ie 2 instead of 1.

Once it's built, if it feels OK, that's it, if it doesn't, ask again.

Yes the crux is definitely the long beams, how many and what size.  I guess I need to phone a timber merchant and get some prices and work out the best bang for the buck from what is readily available.

 

I will still ask my neighbour (who works for a steel company) about steel plates to make a filch beam.  For a laugh I asked him to estimate for doing a steel frame for the whole lot and his answer was "do it in timber"

[Iceverge]

2 minutes ago, ProDave said:

So you are suggesting a 225 by 75 would span 6M if it was not carrying too much load? and suggesting 5 of them

 

Yes but I was being a bit more conservative and suggesting 9. It worked out nicely so that each rafters was falling half way between or on a post too. Honestly, I think I'd need to draw it accurately so I could mentally "jump" on it to see if it looked ok!

 

 

 

 

 

 

 

 

[Iceverge]

My frame of reference for this is a loft we build in a shed on the farm.

 

It's about 6m span with 9*3 sawn timbers @450mm cc. These are full fat, hairy, skin on timbers cut on the farm so there's a good bit more to them than a regularised commercial timber. 

 

None the less they hold , at a guess, about 4tonnes of material although it is mostly more long timber planks so the load is probably partially carried by the planks themselves. I'm not sure if put 4 tonnes of sand up there. 

[dpmiller]

what about cold rolled steel sections rather than timber?