Shed extension.

[benhen31]

Hi all,

I have a shed (this one: Montana Barn in the 12x8 size). I'm going to be making it longer to extend into the dead space currently behind it and add about two meters of length. So I'll be taking the back wall off, extending the sides, floor and roof and then re-attaching the rear wall.

My question is; should I build my new wall and roof panels (Using the same size 38mm x 50mm framing and 16mm shiplap as the original) completely before standing them up and fixing them in place, or should I build the framing upright attached to the existing shed and then clad it once in place?

When the shed was erected it obviously came on the back of a lorry with the panels all prefabricated. The installers simply stood them up in place, screwed them together and then plonked the roof panels on top. Is this a good way to do it or simply done for the convenience of the installation? It was certainly fast. They had the thing done within 40 minutes of arriving!

All the guides I see on youtube have people doing the framing and then cladding in place. However I'm leaning towards prefabbing the panels as that would reduce the amount of time the shed spends with one end exposed to weather (given it's currently full of all my woodworking bits!)

Currently shared space with the motorbike so a few extra metres would allow me to have a workbench that didn't need to fold down constantly!

Does it matter?

 

[artie]

If you are working on your own, you might prefer to frame first and then clad.

If you have help then I can't see it making any difference, except that you could make the panels inside and your time exposed to the weather would be reduced.
Assuming you have somewhere inside to fabricate the panels.

The more important question is how do you intend to extend the roof?

 

[benhen31]

If you are working on your own, you might prefer to frame first and then clad.

If you have help then I can't see it making any difference, except that you could make the panels inside and your time exposed to the weather would be reduced.
Assuming you have somewhere inside to fabricate the panels.

The more important question is how do you intend to extend the roof?

Hmm. I'd kinda thought working on my own it might be easier to build the panels on the ground but yes, I guess manhandling them into position on my own once ready could be a challenge!

For the roof; I'm just planning to copy the existing roof, which is in rectangular panels (two on each side of the peak), screwed into place to create the arch shape - 19mm tongue and groove. Then some felt over the top with some sort of joining gunk to seal the join in felt. Not bothered about looks up there as you can't see the roof really with the position of the shed.

 

[Sachakins]

Wouldn't attempt to join and seal the roofing, best re-felt the entire roof.
I did similar with my shed extension.
I removed the end wall, then boarded up with 3/4 shuttering ply. Then built frame upright and clad after. I ended up leaving the end plywood wall in situ, then cut a door in it for access. So now I have the newer back extension as a separate room. Great for storage, or as a spraying area. Mine house a hobby CNC and laser machine plus work top space on one wall, and 1.8m of steel framed racking at full height on one wall, still plenty of sitting and work space when using cnc and laser, and all wood stored easily. I only use 5-600mm lengths, so stored end on, on each shelf.

 

[Sachakins]

Can't see how much curve on the roof, might be easier to use 9mm ply. Bends easier, and you could stagger the joints, then second layer of 9mm.
You get your 18-19mm thickness, easier to handle and fit especially on your own. Tried roofing mine in full sheets of 18mm ply, it all but killed me trying to get it up there, let alone manoeuvre. . In the end used up the ply on workshop stuff and used 3/4 x 6 tannelised boards and felted over them. But no curve to deal with.

 

[HOJ]

We all have different ways of working, I would make up all the new panels using the same dimension material, and as I call it build off site, you might call it the floor!

Then presuming you have the base sorted/prepped, work on getting the end panel released/out, may not be that easy to be honest if they used ring nails to bang it together.

You've got a Gambrel style roof so 4 panels will work, but I'd use 11mm OSB3 rather than T&G.

 

[benhen31]

We all have different ways of working, I would make up all the new panels using the same dimension material, and as I call it build off site, you might call it the floor!

Then presuming you have the base sorted/prepped, work on getting the end panel released/out, may not be that easy to be honest if they used ring nails to bang it together.

You've got a Gambrel style roof so 4 panels will work, but I'd use 11mm OSB3 rather than T&G.

Yes, that was my initial instinct for the build; using the exact same materials as the original. The current panels are screwed together so once I've emptied all the stuff that's currently on that back wall it should come out relatively simply.

Can't see how much curve on the roof, might be easier to use 9mm ply. Bends easier, and you could stagger the joints, then second layer of 9mm.
You get your 18-19mm thickness, easier to handle and fit especially on your own. Tried roofing mine in full sheets of 18mm ply, it all but killed me trying to get it up there, let alone manoeuvre. . In the end used up the ply on workshop stuff and used 3/4 x 6 tannelised boards and felted over them. But no curve to deal with.

The roof isn't really curved, it's four rectangular panels that are connected at angles to make the slightly angular arch shape. I'm trying to match everything to the existing so that it looks like it was always meant to be that size.

 

[benhen31]

Wouldn't attempt to join and seal the roofing, best re-felt the entire roof.

There'll be a join even if I re-felt it due to the size. It's only a few years old so the current stuff should be fine condition wise.

 

[TomGW]

Do you even have room to clad the new sides if you frame in situ, particularly between the gable wall of the house and shed?
Your first task will be to extend the timber floor, level and on plane with the original. Only then will the new, square, wall panels fit precisely in place.
One advantage of framing and cladding in situ is that everything will be cut to fit and accommodate any deviation in the floor.

 

[benhen31]

Do you even have room to clad the new sides if you frame in situ, particularly between the gable wall of the house and shed?
Your first task will be to extend the timber floor, level and on plane with the original. Only then will the new, square, wall panels fit precisely in place.
One advantage of framing and cladding in situ is that everything will be cut to fit and accommodate any deviation in the floor.

There is space as the area being extended actually goes past the rear of the house so is pretty open.

That's a good point about things being perfectly square though. A small 10mm deviation is no biggie if I'm framing in place but would leave a gap if the panels were all nice and square pre-made. Very good point. This might swing it for me!

 

[TomGW]

There is space as the area being extended actually goes past the rear of the house so is pretty open.

That's a good point about things being perfectly square though. A small 10mm deviation is no biggie if I'm framing in place but would leave a gap if the panels were all nice and square pre-made. Very good point. This might swing it for me!

When you have the room to work around the outside of the shed I think framing in place is the easier method.

I would suggest that you brace the shed internally with a couple of diagonal braces, plus a cross brace at wall plate level and prop the ridge, before you remove the back, in order to prevent racking or collapse. I would be concerned that, with the gable removed, the 4 piece roof panel construction is inherently less rigid than a simple pitched roof. The last thing you need is the whole shed to spread out of shape when you remove the gable end.

Do consider inserting a 'ridge beam' to support the longer roof. The current setup essentially has a double ridge beam in the form of the two, top panels and you are going to break that by extending. There is a good case for keeping an internal partition at this point to support the roof.

Then staple a bit of pvc sheeting across the gable to keep it dry while you extend.

All the best with your project.

 

[benhen31]

When you have the room to work around the outside of the shed I think framing in place is the easier method.

I would suggest that you brace the shed internally with a couple of diagonal braces, plus a cross brace at wall plate level and prop the ridge, before you remove the back, in order to prevent racking or collapse. I would be concerned that, with the gable removed, the 4 piece roof panel construction is inherently less rigid than a simple pitched roof. The last thing you need is the whole shed to spread out of shape when you remove the gable end.

Do consider inserting a 'ridge beam' to support the longer roof. The current setup essentially has a double ridge beam in the form of the two, top panels and you are going to break that by extending. There is a good case for keeping an internal partition at this point to support the roof.

Then staple a bit of pvc sheeting across the gable to keep it dry while you extend.

All the best with your project.

Yep, I'm planning on putting up some temp framing to hold everything in place whilst it's dissasembled. I may add the ridge beam idea though. Don't want an internal wall but I could definitely go with the beam.

All excellent advice, thanks!