Suggested Joints for wooden porch

[twm.bwen]

Hi there, am building a porch similar in basic design to the following

The framework will be timber and I'm currently trying to work out what joints to use where and need help with the following:-

As I cannot seem to find a supplier of a 200x45mm sill I will machine it myself. But cannot work out the corner detail ie how to join the mitred sill parts and join the corner uprights in a strong way. (M&T corner into mitred joint?)

Sill will be frame fixed to dwarf wall and "Wall Upright" will be frame fixed to house wall.
NB Corner upright will be square post not like in sketch.

I will M&T "Glazing uprights" into sill and "wall plate", fine. But how do I join the corner upright to the mitred (and ply biscuited) sill and wall plate.
Also, how do I secure "wall upright" to the Sill and "Wallplate"

"Wall upright" will be bolted to wall

Sorry, if you are as muddled by my description as I am.
So any ideas, any books or websites om framing for a similar porch?

Thanks for your patience,
Tom

 

[^woody^]

First, lets do the window parts!

A frame has a cill at the bottom, the "uprights" are jambs, the "glazing upright" is a mullion, and the top of the frame is the head

The cill would be a common section available from timber merchants. Might be better to buy this, rather than machine one and risk warping and splitting etc.

You should also consider having a corner post (100x100 or 75x75 depending on the frame section sizes) and not joining the two window frames at the corner.

Also your "wall plate" can not be the window head - you need an additional timber across the top of the frames to take the roof load

You can biscuit or spline joint the cill, but if you tenon the corner post into the cill, then this will be a stronger joint

All the frame sections are generally mortice and tenon joints

 

[big-all]

what ever you do do not use ply for a window cill

just buy a cill put a groove in the back with a router/table saw/buiscut joiner and cut the back out of a window board leaving 6 -9mm to fit in the slot
the top of the board is level with the top off the groove with no shoulder so no gap will apear

 

[twm.bwen]

Excellent, Thanks Big All and Woody for your replies.

Glad to know the correct terminology. Had I known I could have saved myself the hassle of doing that damned sketch, so thanks.

I certainly shall be using a 75x75 corner post, it was just easier to draw it as individual elevations.

So I can do a mitred spline joint for the cill (but NOT using ply for the spline) and then cut a mortice into it (say 60x60) for the corner post tenon and that should be strong enough. correct?

If I understand you correctly you mean joints similar to these

With regards the Cill I cannot find a local supplier with 200x45 cill ex stock and to have one machined will be nearly £70 (which sounds a bit steep to me, am I being tight?)

 

[^woody^]

Why do you need a 200mm cill section?

Standard ones are 140/150mm and are common. About £10-15 per metre for softwood , IIRC

Don't have a spline joint cut right to the front of the cill. You only need this in the centre or rear part of the cill

 

[twm.bwen]

Why do you need a 200mm cill section?

The wall is a single skin of sandstone about 140mm wide, I'd like the cill to act as both the interior cill and the 'sole plate' as well.

I want to build this porch as well as I can, my physical carpentry skills for the cutting of the joints is really quite alright but its the lack of knowledge and experience in design and choice of joint that is holding me back.
And i can't find generic detail on joints and design anywhere on the web.
Thanks

 

[morrik27]

If you get a standard cill from your timber merchants it should have a square solt in the back to fit a rebate in the back of the window board to slot into. They will be able to supply the window board as well at the same time if you wish.

These will should also be available in different depths to suit your needs, and the joint will look as though it's all the same piece.

This will also be MUCH cheaper than getting one machined to order.