Building 'lean to' shed against existing wall?

[macleod92]

Hi there,

So I'm planning on building my first shed and the space where I'm planning on having it backs on to an existing wall of a garden room.
There's plenty of information out there about building stand alone sheds, but I've been struggling to find information on building one against an existing wall.

My initial thought was to build a stud wall directly against the existing wall and put flashing around the edges to make sure it's weather sealed. The plan is then to put insulation and plasterboard throughout the inside of the shed.

I've attached pictures which show the garden room (just to provide some context) as well as a picture of the wall I'd like to build against. As you can hopefully see from the pictures (I've also included some from the inside of the garden room) there seems to be some evidence of damp on the wall.

My concern is that if I build a stud wall directly against the other wall then I'm going to run into some issues with damp.

With this in mind, what's the best way to go about doing this?


Thanks in advance for the help, I really appreciate the advice!

[ahfix]

What do you plan to use it for?

If there is any chance of damp then I'd avoid the plasterboard as it'll just start to break up.

I guess what you want to build is a three sided shed with the fourth being the solid wall. In that case you could build attach treated timber as a frame (left, top, right) to the wall and then start to build out your walls from there. It's hard to tell, the ground looks paved so you'll either need a decent base either by digging out a footing or building up from ground level.

When I installed my timber shed i used concrete blocks (leveled and fixed in 6 inch of mortar) which sit 4 inch off the ground at the lowest side with timber bearers running over those.

ah

[macleod92]

Thanks for the response!

The plan is to use it as a workshop space. I live in a very built up area so want it to be a soundproofed (dampened) as possible. Hence the plasterboard as it's dense, but a lot cheaper than other sheet material.
For the base the plan is to dig up what's already there and make a concrete slab. Beyond that my aim is ultimately to have a watertight room.

Regarding whether or not the plan was to have the fourth wall as the solid wall rather than a stud wall; I'd rather it was a stud wall as opposed to just the solid wall. That way I can insulate it and mount things to the stud work rather than drilling lots more holes in the wall itself.
That said I was hoping to find out my options. If it's not going to be possible to build a stud wall coming off that, then I'm not opposed to just going with the solid wall.
I just don't want to cause myself issues as a result.

[ahfix]

If you're not using the brick wall as a shed wall then it's not really a lean to

When you build up against it then you have a high chance of damp ingress from the wall, plus possible splash back from rain hitting the wall or dripping from the coping above. If you're going for a classic "four wall" build then keep the shed 0.5 or so from the wall, this will allow you access around to repaint etc and also avoid the issues above.

ah

[ahfix]

Thanks for the response!
For the base the plan is to dig up what's already there and make a concrete slab. Beyond that my aim is ultimately to have a watertight room.

This is a common method but I really couldn't be bothered for my shed. The previous owner of the house had 'acquired' 3ft long kerb stones and used them for the border of a veg patch. I broke them in half and used them as pad stones to build the shed base on to. I didn't have enough kerb stones so used concrete blocks where I ran short. Shed hasn't moved.

Worth thinking about if it saves you back breaking work digging up and then pouring a base.

ah

[macleod92]

Thanks @ahfix

Sounds like (for the sake of avoid damp issues) I'd be better off building a stand alone shed and making sure to space it away from the wall.

Thanks for the advice!