The Car Port

[ProDave]

At last, I am starting the final unfinished project, the car port.  It will measure 6 metres by 6 metres comfortably giving covered parking for 2 vehicles.  So now I am planning it's build which I hope to start soon.  However it has got a bit more complicated due to changing one of our vehicles and it now needs a minimum height clearance of 3.2 metres under it.  Some aspects of this will be dealt with on the hoof as we encounter them.

 

But the first issue is the supporting posts.  I already have 6 150mm square larch posts that have been sitting on my trailer for a few months after being delivered from the saw mill.  These are to be the main structural uprights.

 

The plan was to get my neighbour to fabricate steel post foot brackets, as he did for similar ones for the balcony.  They were a simple U shaped bracket that bolted to the concrete and the post sat in and bolted through keeping it off the ground.

 

But there is a complication this time.

 

These are the posts on the garage side.  I want them to be close to, but not touching the garage wall.  The issue is this aligns them with a drainage channel that was cast into the concrete when poured.  This serves to take rainwater falling on the concrete away to the rear and keeping it from puddling against the wall.

 

I throw it open to the creativity of the forum to suggest a suitable bracket.  It will have to straddle over that drainage channel but be fixed down to one side on the flat part of the concrete.  The post will be secured to the wall near the top for stability.

 

For clarity, the real posts are much longer, this is just a mock up of how the post will sit using a short offcut from the balcony posts.

[saveasteading]

U shaped bracket, with 2 rods projecting down either side of the channel. Concrete base beneath the channel.

OR set the bases to miss the channel and the timber construction revised to fit.

[ProDave]

This is the best I can come up with

 

 

 

The base will straddle over the drainage channel with a fixing either side on the flat concrete

 

The sides plates are chosen so the fixing bolts go through the post parallel to the wall, making them easier to fit and anything sticking out is less of an ankle catcher.

 

Can anyone see any issues or improvements?

[saveasteading]

1 hour ago, ProDave said:

any issues

No that looks good. I had in mind it having bars sticking down but bolting down is much easier so I agree with that.

I'd just say to make sure that the concrete base goes well under the channel, in case the load all wants to go down the narrow side at the wall.

I've a feeling you can buy that ready made.  Yes just looked and SF have them but only up to 100 x 100 (sabrefix) . Perhaps search further.

[saveasteading]

You can get that ready made in half's. No bottom plate but with heavy fixings it might be OK.  I can't cut and paste them for some reason.

[ProDave]

Back again.  Good job I built the rest of the house quicker than this car port.

 

So I have the 2 posts adjacent to the garage up, and have some lengths of 9 by 2 C24 and starting to mock up how it will actually work.  My first question is what is the minimum fall I can get away with on a box profile steel roof.  Bearing in mind this is a car port and if it's too low, any leakage e.g. at a joint is not a disaster like it might be on a proper roof over a building.

 

My initial on the ground mock up suggests no more than 10 degrees and I would like it as low as 5 degrees.  I am sure any roof supplier would say that is too low, but I have to build this quite tall and I am trying to avoid the front edge being ridiculously high once the back edge is at the required height.

 

Pictures later when I hopefully have made some progress.

[saveasteading]

6 minutes ago, ProDave said:

minimum fall 

 I put up hundreds and the favoured slope was 10%. That's about 6°.

But you have to build it well especially at laps, because wind will drive it up that slope. Good screws too.

 

In theory it can go flatter than that, but it gets riskier esp with thin cladding that can bow.

 

Your average roofing supplier or contractor prefers steeper as  the build quality and risk reduce.

[saveasteading]

Why not go steeper? It increases ridge height and gable areas. Wind loads usually increase.

So cost and appearance.

 

Check out the purlin centres for   whatever cladding you favour.

Plus the available profile fillers for the ridge. High quality mastic tapes (not subject to uv) at all joints. Stainless screws with a washer that winds down the thread. No leaks.

 

Coatings are improving, but Plastisol may still be available in the old spec, where there is 'cut end peel'. ( the coating separates at the end, then it rusts) Ask so you can avoid it.

[ProDave]

It's a single slope so no "ridge"

 

At my present 5 degree ground level mock up that will put the front of the car port just over 300mm higher than the back.  I need 3.2m clearance at the back, that will make it 3.5m clearance at the front.  That is going to be above the eaves height of the garage it is joining to so it is a question of will it look ridiculous or not.  I hope to get a mock up later and take a picture.

 

The length of the roof will be 6 metres.  I was hoping to find a roof material supplier that can do 6M in one run without joints.  I might be over optomistic there.  If not I will spec the overlap as a bit more than normal, but as I say not the end of the world if a little rain leaks.  If it is windy enough to blow some rain up the joint, it will be lashing in at the open rear of the car port anyway.

 

Re coatings.  I hope to get them supplied to the length I need so nothing needs cutting, like I did with my sun room roof.  That has given no problem so I will look up what make it was and they will be my favourite all else being equal.

[saveasteading]

OK that's helpful. You will presumably flash the uphill end, so that still  needs sealing or the rain will run back inside.

The cut end peel problem applied at the factory cut, and they suggested a varnish that sealed it. You can see the issue on some old sheds.

 

6m is generally easy to source but you might not have much choice of stock material from a local supplier. 

[ProDave]

Photo time

 

First beam hoisted and fixed (not properly for final fixing)

 

 

That's at 5 degree slope, front is about 300mm higher than back.  It does not look as ridiculous as I first feared, although it is above the eaves, it only slightly breaks the line of the tiles.

 

Joists will span sideways at 400mm centres to a similar beam the other side and that will be supported by 3 posts.  The two side beams will be doubled up and I will brace these overhangs back to the posts on the garage side.

 

I might try the front just a little higher before I decide.  the posts won't get cut to length until the very end.

 

And this is why it needs to be so high.

 

 

There is presently 12cm clearance under the rear beam.  We need to do a trial demount before committing to this height because jacking it up takes weight off the springs and the truck rises, so we need to make sure there is enough height to do that.

 

[saveasteading]

I've just looked at a cascading supplier and see that they have some with incredibly thin steel. So do check tge options for their properties.

 

You will get snow build-up/ drifting with that abutment of almost flat roof and gable wall. So don't under-do the strength of battens. Cheaper to have extra wood than pay for a design.

 

Are you having a gutter or letting rain run off?.

[ProDave]

Front edge and left side edge will want flashing.

 

Rear edge will have a small overhang for gutter.

 

The edge adjoining the garage will not be flashed in.  Far too complicated.  There will be a small gap and the fact rain will run down the wall does not matter.

 

Snow here sticks to the 45 degree tiled roof so no amount of slope will stop it sitting on this roof.