is Timber 100 x 47 x 4200mm good enough for car port? help please ;)

[sean oc]

I have a car port i want to build.

Just over 2m wide and 4m in length

I was going to sick 3 100x100mm 8 foot posts in the ground on each side, so 6 in total

would this be okay to use to sick around the top to fix to the posts to support the roof,
100mm wide so will sit nice on the top of the posts and is long enought to be in once piece?

ps. roof will be boarded and felted.


Thanks Sean

Sawn Tanalised Treated Timber 100 x 47 x 4200mm
http://www.huwsgray.co.uk/shop/sawn-tanalised-treated-timber-100-x-47-x-4200mm.html

 

[sean oc]

or do i need thicker timber?

thanks

 

[JohnD]

Are you thinking of putting these beams flat on top of the posts? They must be vertical because you have to maximise beam depth.

 

[sean oc]

Are you thinking of putting these beams flat on top of the posts? They must be vertical because you have to maximise beam depth.

Hi yes i was going to lay it flat so the 100mm fits the 100mm on top of post.
From your reply i see it may not best way then, im struggling to find a 4m+ post long enough, as surely its better to have it one length than two seperate beams that meet on middle post?

Thanks

 

[JohnD]

For mine, I had 6m lengths delivered from a local timber yard. They would not be safe on a car roof rack. DIY sheds may not sell long pieces.

You can use gallows brackets to improve support. They also provide triangulation so improve rigidity and reduce wobbling which will loosen and weaken the joints. You can rebate the side of the post so the beam sits on the ledge, and retain with a large coach bolt.

If you do have to use more than one piece per side, overlap them.

4m is very short for a car port. Rain is not vertical. Ensure the middle legs will not obstruct the car doors. You could make it longer and use four posts each side so there is not a middle one. The end posts need not be at the very ends of the roof, it will be a bit more rigid if they are a foot or so inside.

If you put the legs into the ground they will rot.
Concrete pads plus steel supports, or concrete spur posts, will lift the posts out of ground contact. Soak the ends of the posts in spirit-based wood preserver.

Boarding and felting will be heavier than polycarbonate. I think for a boarded roof you will need larger beams. There are tables of beam sizes required per length and load, I do not have a link to hand.

 

[bernardgreen]

Soak the ends of the posts in spirit-based wood preserver.

And / or put a pad of lead between end of post and the concrete pad. This will [a] press into and thus seal the end grain of the timber and create a cushion to spread the wieght of the post evenly over the ( rough ) surface of the concrete and across the full area of the end of the post.

 

[sean oc]

For mine, I had 6m lengths delivered from a local timber yard. They would not be safe on a car roof rack. DIY sheds may not sell long pieces.

You can use gallows brackets to improve support. They also provide triangulation so improve rigidity and reduce wobbling which will loosen and weaken the joints. You can rebate the side of the post so the beam sits on the ledge, and retain with a large coach bolt.

If you do have to use more than one piece per side, overlap them.

4m is very short for a car port. Rain is not vertical. Ensure the middle legs will not obstruct the car doors. You could make it longer and use four posts each side so there is not a middle one. The end posts need not be at the very ends of the roof, it will be a bit more rigid if they are a foot or so inside.

If you put the legs into the ground they will rot.
Concrete pads plus steel supports, or concrete spur posts, will lift the posts out of ground contact. Soak the ends of the posts in spirit-based wood preserver.

Boarding and felting will be heavier than polycarbonate. I think for a boarded roof you will need larger beams. There are tables of beam sizes required per length and load, I do not have a link to hand.

Thanks for the info.

Limited on space due fence and tree the oppsite side, its only in the corner of the garden to house a small classic car for storage mainly (even so it will be a little tight)
Saying that the concrete base is 4x2 m
The gallow brackets looks like a good idea, think ill over lap possibly

Soak the ends of the posts in spirit-based wood preserver.

And / or put a pad of lead between end of post and the concrete pad. This will [a] press into and thus seal the end grain of the timber and create a cushion to spread the wieght of the post evenly over the ( rough ) surface of the concrete and across the full area of the end of the post.

Thanks for info

I will use the gallow brackets they will help, its only due to space my concrete raise base is 4m x 2.5m is only to store a classic car under it it will just about fit with a little room to open the door.

I suppose i could move the posts out a little for some more room, i will be building walls to it eventually ... when i have the funds so its like a small shed/gagrage.

The posts will be in the ground, so i will have to soak them to slow down the rot.

Cheers

 

[sean oc]

Are you thinking of putting these beams flat on top of the posts? They must be vertical because you have to maximise beam depth.

Hi could i not does this?



or would it not be strong enough to carry a boarded roof etc?

If not ill use 100x100mm posts and tops bars also

cheers

 

[JohnD]

not sure I understand your drawing. If the 100x100 is the leg, are you looking at it from above? Or from the end of the carport?

The beam should be running horizontally, on end, so your drawing should show the 100mm width of the leg, with the cutout, and the height, which is much more than your drawing suggests, that's what I had in mind. But cut the leg to the full depth of the beam, and bolt together, will be less able to tip over during construction or strong wind. The depth of the beam is much more important than its width. e.g. you may need 170x44

Somebody will be along with the table of beam depths, I expect.

 

[sean oc]

not sure I understand your drawing. If the 100x100 is the leg, are you looking at it from above? Or from the end of the carport?

The beam should be running horizontally, on end, so your drawing should show the 100mm width of the leg, with the cutout, and the height, which is much more than your drawing suggests, that's what I had in mind. But cut the leg to the full depth of the beam, and bolt together, will be less able to tip over during construction or strong wind. The depth of the beam is much more important than its width. e.g. you may need 170x44

Somebody will be along with the table of beam depths, I expect.

I see, like this full depth of beam, and with the 107x44 you can sink into the beam as such but cutting down 170mm and using some coach bolts to secure it.
Surely this would make a nicer solid fit, than having a 100mmx100mm post stuck on top bolted down?

Thanks for your time replying

 

[JohnD]

yes, that's it.

I would only use one large coach bolt, perhaps with penny washers, in each joint. If you use two screws in outdoor timber it may cause a crack with expansion and contraction from the weather. I am near the coast so I used stainless bolts and screws, not very expensive as you only need a couple of dozen of the big ones.

BTW I used decking timbers for some of my frame, they may have been something like 150x37 and are easily obtainable, pressure treated. Avoid any with big knots.

I am not much good at woodwork so benefitted from advice on here from the old hands.

edit: try this. It is for floor joists but there must be one for flat roofs, if you search.
http://www.easi-timber.co.uk/downloads/BSW_Easi_Span.pdf