Re: Shed floor needed on concrete base?
Just seen this one from https://forums.hexus.net/home-garden...new-shed.html:
Quote:
Originally Posted by
Saracen999
I'm not expert, but my approach to a concretebase was to get the shed clear of touching it. A good base, which essentially decent quality (as in outdoor-rated, properly treated base of 2x4, with the 4" side vertical (i.e. givig a 4" ground gap) and then a heavy sheet of watrproof ply (I think it was 3/4" or about 18-20mm,might have even beem a inch thick) provide the base on which the whole shed sits. The actual shed skin was about 1/2" or 15mm (yeah, I know 30mm <> 1 inch) thick, whick pretty much ensures it won't warp/shrink and therefore leak.
So I guess the intention is that the treated 2x4 wood makes contact with the ground and deals with the moisture so the floor and the bottom of the walls do not? And air can flow under the floor (although inside the actual shed it's still as sealed/ventilated as you make it). The wall cladding would then not touch the floor either even if it was slightly proud of the wall frame at the bottom to cover the base (is that a good idea?).
Re: Shed floor needed on concrete base?
It makes sense to me.
I think the bigger issue would be ensuring you have a weatherproof seal all around the sides and roof, as it's right against the house wall. We have a similar entry-way thing* on the side of our house, but whoever built it forgot to include lead cladding over the roof joint!
I like The Carpenter's Daughter site, though. Very good find!
*No idea what it should be called - Wooden house extension in front of the front door, bigger than a porch, it's basically another full-size room with a second room and toilet off to the side. Most fitting term I could find was a barbican!
Re: Shed floor needed on concrete base?
The major thing to think about with a wooden structure is moisture.
If wood surround means the formers used when pouring the concrete slab, which are in contact with the soil and potentially your shed, then they will wick moisture. Placing your shed timber in contact isn't the greatest idea. You can remove those and simply deal with the concrete base.
In the US, timber framing on a concrete slab is the normal method of house construction. Typically there is a purpose designed membrane between the wood and concrete for air, moisture and insect sealing. For a shed, you probably don't need to worry about any of those things.
What you should focus on is thinking about where the water will go. Use overhangs, so that your pressure treated bottom plate doesn't end up sitting in a pool of water. Ideally your sheathing can overhang the edge of the concrete preventing that surface from collecting water.
Re: Shed floor needed on concrete base?
Cheers both.
Yes I've considered the roof to wall join - might need to call in the builder for that one. Not sure I want the cost of lead but after a bit of reading it seems you can just chip out some mortar, feed in the felt and re-mortar on the join. Won't be the prettiest thing in the world but I won't be able to see it!
Re the floor. The wood looks a bit more sturdy than just throw away boards and are round all 4 sides including against the wall. But on two sides it goes down to drainage space so wouldn't want to rely on them for load bearing. One side is level with and butting up against decking and the other is against the garage wall. Will take another look at the two exposed edges and decide whether to keep our remove or just to treat and try and keep the water off.
Aiming for a single slope away from the garage wall for the roof. Will have some overhang all round and is a fairly sheltered space so hopefully all the water will stay away! Guess I could gutter if feeling keen and feed it down into the ditch.
Will try and grab a decent picture on the space on the weekend :)
Re: Shed floor needed on concrete base?
rain splash zone IIRC is typically taken as 150mm above concrete. If you can tolerate a step-up into your shed use driveway paviors/frost resistant bricks to raise the timbers off the ground. This allows under-floor ventilation so the floor panels should last longer too without worries about damp going underneath and not being able to dry out. Set back the supports so the shed overhang shelters the bearings of the shed onto its supports and prevents direct wetting.
Treat all exposed timbers ideally start with pressure treated wood and then give all cut ends with 2x coatings (or a good soaking) of end grain preservative such as ensele (others are available)
After that has dried coat all the wood with decent preservative-finish coat for external use. Some include stains too if you want a particular colour etc. Depending how long you want the thing to last consider only using fixings that are suitable for external use - these will be more expensive. You probably don't need stainless, hot-dip galv is probably sufficient, just be consistent and match the fixing materials to the brackets etc.
NB to allow for mastic joints between the timbers and your brick wall, and use some slotted galv or stainless tie brackets to restrain the panels back to the masonry but allow it to move vertically as the timbers and brickwork will want to expand/contract at different rates. Any roof flashing should similarly be lapped and jointed to allow for movement.
Any panelling you use should ideally be OSB3/OSB4 and ply to BS-EN636-3 to deal with external conditions. Note you still need to add surface treatment to the panels, the specs deal more with the glues used in the panels to make sure they can handle the humidity. The sort of tropical hardwood that could also resist external exposure without treatment generally isn't available (and rarely sustainable ergo illegal if anyone tried to do it).
Re: Shed floor needed on concrete base?
Quote:
Originally Posted by
jimbouk
Aiming for a single slope away from the garage wall for the roof. Will have some overhang all round and is a fairly sheltered space so hopefully all the water will stay away! Guess I could gutter if feeling keen and feed it down into the ditch.
Will try and grab a decent picture on the space on the weekend :)
One thought on water path, and this is not my area of expertise so this is simply a wondering for consideration by someone who actually knows about this stuff:
If the roof slopes down away from the garage wall then having a gutter along the side edge above the fence will stop it gushing water onto the fence and rotting that. =Happier neighbour. Yey! Rather than send it via downpipe into the drainage trench, (does that risk softening the ground locally and affect the garage concrete base/fence base?), why not pipe the gutter into a water butt at one side of the lean-to and get some eco-points for harvesting water to use in the garden/help wash the car or whatever? I can't see any benefit in guttering the two sloping short sides, and I imagine it would look odd too.