Help with greenhouse build

[MickCheese]

I have been tasked with replacing our greenhouse that has finally fallen down.

I like the Victorian painted wood style so am thinking of softwood 75mm X 50mm.

It will stand on the existing dwarf walls and is about 8' x 10'.

So firstly have been thinking about the profile of the rails and styles. I have to be able to cut them myself using routers, table saw, band saw etc. I would consider the purchase of a Domino if it would make things much easier, I do have a bench top mortice machine.

Here are a couple of rough sketch-up drawings so you can see my thinking. Not sure I would be able to fabricate these without a spindle moulder though. Don't anyone say cut them by hand, there would just be too many and the margin for error is huge.

Am I on the right track? I've never done anything like this before so welcome some guidance. The joint looks quite complicated to fabricate in my home workshop, am I complicating this too much.

Mick

 

[Phil Pascoe]

I would think for a joint in outdoor softwood the simpler the better. Have you considered W.R.Cedar?

 

[blackrodd]

Looks pretty good to me, As you say, It helps to keep things simple.
If it helps, draw a "skid", a full size of each of the different joints to work from.
I Suggest you make the cill from oak or similar hardwood and let the roof run over the side windows, about 6", fit guttering and capture the rain in the usual water barrels.
Keep us posted if you can, it'll be interesting.
Regards Rodders

 

[MickCheese]

Thanks Rodders.

Just looking at my sketch again I could use my woodrat for most of it providing i Can get the wood between it and the floor but as its on a dwarf wall it may just fit.

Really looking for ideas how to and in what order to cut a joint like that. I will try some test cuts in some 3x2 when I have some time over the weekend.

Mick

 

[RobinBHM]

A greenhouse is an interesting project -and challenging as all the joinery is on show.

I would keep to a single 1/2" tenon.

For marking out purposes, as drawn the tenon is in the moulding, not the rebate.

On the outside you could make the jambs and mullions flat, ie with no rebate and then make flat beads with rebates at the back. That way the beads form both the rebate and glazing bead at the same time. The head of the frames could be made thicker then grooved.

I wouldnt form a rebate at the bottom of the frame whichever way you make it. If using flat beads as above, the glass can be made to stop about half way down the bottom of the frame and stop against plastic clips.

Inside you could make the frame square section and pin on the moulding. For ease, the head of the frame and bottom of the frame could be made out of 100 x 50 section, then plant your moulding onto the jambs and mullions. This means no scribing cuts. Planting on the moulding works really well if it is an ovolo as you can set the piece back by 4mm which forms the quirk.

If you prefer to make with moulding included, then either keep head and frame bottom square, or chamfer and cut the scribe with a sliding mitre saw or table saw with slide.

 

[MMUK]

Why cut complicated double mortise & tenon joints? They won't be seen so why not use a simple single mortise & tenon?

 

[Phil Pascoe]

That's what I was getting at.

 

[MickCheese]

All suggestion gratefully received. The reason I included a double M&T was just the width of the joint in a 3" piece of wood.

I will try a couple of mock ups but was hoping someone with more experience would suggest alternatives, I don't want to re-invent the wheel.

Mick

 

[dickm]

Can't remember for sure, but the softwood greenhouse I had some 30 years ago definitely used single M&T, but with the tenons horizontal. It's easier to make, and possibly less susceptible to water ingress, although the G/H rotted out in only about 10 years, even with some interim painting. If you can afford WRC, then it would be a better reward for all the hard work of building it.

But being a practical sort of gardener, even at my age, I'd go for aluminium!

 

[MickCheese]

All your comments are being assessed so really appreciated. Will WRC paint OK?

You've all convinced me with a single tenon.

I was a little worried about the planted on moulding as it was just another place for water ingress. But have I misunderstood what was being proposed?

Mick

 

[MMUK]

WRC will paint ok but personally I prefer to use a clear stain.

As for plant on mouldings, seal the back of it with a couple of coats of waterproof pva glue and apply a thin bead of clear silicone to the top edge before fitting.

 

[MickCheese]

Thanks for the info.

Actually feel I am getting somewhere now. This is not something I have attempted before and it's a big project so would really like to get things straight in my mind before I start.

Mick