Building joined to house, any idea's please.

[Honeybea]

Hi, i'm going to have a shed/outhouse/summer house joined on to the back of my house. I have added a photo so you can get an idea of what it will look like. The area the base is to sit on is concrete and on top of this is decking, so we are going to put a waterproof sheeting down then a proper thick wood floor, then vinyl on top of this. I want it to look like a shed but on the inside I want insulation and then OSB boards so it gives it two walls and then I can paint the walls. I have people to help build ( friends and family) but i'm left to get materials etc and this is where I am stuck. I know I need OSB boards but what thickness should I use, I will be going for the
8 X 4 in size, is this the best size to buy!

On the outside I want it to look like a shed so what is it I need to buy!

I will be getting lots of 2 x 4s, is this all I will need for the supports, roof etc.

On the roof do I just need OSB boards and rolls of waterproofing.

I am not a diy person so I just can't remember all the names for the items I feel I need so do bear with me. The insulation with be the thick things with silver foil looking stuff on the sides. See what I mean about not knowing the names, what is this insulation called.
I am going to try and source as much as I can from free sites and buy the rest. Once I have got it all I have all the help I need to put it up, I just need the brains in knowing what I need.

The shed will be about 8ft by 8ft with a door on one side and I want as many windows as possible. The people building it want to go for double glazed upvc windows but I'm a bit worried about it all holding in the strong winds we now have, has anyone had this sort of shed/summer house built with upvc windows.

I appreciate any replies.

 

[r896neo]

I replied to your first thread about this shed and my concerns especially about the floor are still valid. You are creating a rot and condensation haven in your proposed 'floor' the way you describe it. I honestly think you could throw quite a few quid in materials into this venture and be left with a damp, draughty condensation filled space which will be unusable as anything other than a shed after its first winter. Consider if its more sensible to save up until you can afford a small extension.

If you are going ahead then here is some info. The roof of a shed is normally a single layer of mineral felt as the most basic, next best would be torch on felt (2 layers, a base sheet and a cap sheet) next best would be epdm which would be used on extension flat roofs etc.

Insulation in rigid board form is called PIR boards but most people will refer to it by trade names like kingspan or celotex.

You should use 18mm osb throughout. Many sheds would be made of 12mm but the cost difference is small and the thicker stuff is much stronger. Generally sheds are finished on the ouside with shiplap/ weatherboard cladding but in your case if your putting insulation in the walls you should strongly consider a breather membrane over the studs on the exterior and counterbattens and cladding on the outside of that.

You must securely fasten your building to the house wall both at the roof wall plates and the walls. You should use a ceiling joists to create a truss type shape (triangle) rather than just using rafters as a mono pitch as this will stiffen your building and because you are not building a box but a 3 sided lean too its important to provide some stiffness with the roof structure. You must use a flashing along the joint between roof and house wall, either lead or a lead free alternative like ubiflex. You can use flashband as a cheap alternative but its cheap for a reason.

 

[motorbiking]

Are you ready for the amount of light that will be lost in your house? That.. lets call it an orangery will block quite a lot of light. Having built a man cave at the bottom of my garden.. I'd personally go with:

Double underlay and overlay roofing felt overlapping 50% each sheet, so there are effectively 4 layers.
OSB 18mm for the roof, floor and walls
just under 600mm spacing for the roof joists doubled at the ends, so effectively you have a SIPS type arrangement with a central joist
3 horizontal noggin off-set for ease of installation and rigidity.
70mm celotex all round (I used 100mm, but since you are using 2 x 4, the 100mm wont fit. If you are worried about fire resistance, then maybe rockwool instead.

I'd consider a 2 x 6 for the wall plate, I'd also consider bolting the uprights to the floor in some way. and screw the walls to the floor.

I really think you need to think about some light panels in the roof, maybe you can find some second hand velux windows on ebay.

I'd look at a t&g external cladding, non-treated is a lot cheaper and its fairly easy to treat yourself. (2 coats of preserver and 2 coats of wood stain).

you also need to consider drainage. Unlike the picture in that ebay option, you need some rain water collection at the lower edge ideally in to a soakaway dug in your garden.

Are you sure a conservatory might not work better?

Also don't block any vent bricks (like in the picture) and you definitely want a better job that the design in those pics. A horizontal wall plate beam will give a lot more strength than a few vertical supports.