Garden/Office floor concrete or wood

[forward]

Offife/Garden room: Would prefer timber joists and floorboards over concrete. internally it would be circa 2.5 mrts squared.

What distance is required between sub soil covered with DPM and joists. I take it some air bricks would be needed?

Although not a big deal what is the kind of price difference between concrete and wood floor?

Thanks

 

[Ivor Windybottom]

Would you use it in winter? Concrete with insulation under won't make your toes go numb, a suspended wooden floor would.

Also how long do you want to stay there? Wood always rots eventually.

Our old shed wasn't actually rotten, but the rats had still chewed a big hole in it and took up residence there. Rats don't chew concrete!

 

[23vc]

If DIYing it, probably not a lot of difference in cost.
I’d go for concrete too, and did on mine. With floating 100mm PIR and flooring on top. But mine was small enough to do it in about 30 belle mixer loads, and not need a readymix delivery
Suspended timber needs ventilation and proper detailing to prevent it getting damp, and still needs foundations of some kind or ground screws etc, all adds up

 

[mrrusty]

Agree with above. Quickest way is to make some formwork (cheap timber and roadpins), get a barrowmix company to fill it with concrete and level, and then build on top. It wants to be high enough that the frame sits on the edge and the cladding goes down over the edge of the base to shed water below the floor. An easy way to create a raised lip around the edge of the slab base is to use concrete lintels. Fill the floor between lintels with DPM, PIR and floating floor inside.

 

[forward]

Sorry for delay in getting back. Thanks for replies. Useable in colder times a must. At 78 I might not be around that long (smiling) but it will be built to last. I Intended to use foundations then semi eng bricks with rafters suspended on joist hangers so should stay dry. Perhaps with insulation under. However will take your comments on board.

 

[mrrusty]

If you are looking at a suspended timber floor, you might want to consider easypads as an alternative - heck of a lot less work (and much less material to dispose of) - dig some holes of an appropriate size and depth, fill with wacked MOT, place easypad, adjust height, place timber frame. You can fill the timber frame with insulation and floor over. https://easypads.co.uk/ https://shedbasekits.com/wp-content/uploads/2018/03/2.EasyPads-How-to-install.pdf

 

[Ivor Windybottom]

Perhaps the seasoned builders can confirm or deny, but I doubt that any house builder is building in suspended wooden ground floors any more. The time and cost involved in insulating under it will be more than building up from the ground and putting a slab of foam under or on top of the concrete. Usually suspended floors are only retro-fitted with insulation where they already exist, i.e. in old houses.

Also wood is very expensive these days.

 

[mrrusty]

Perhaps the seasoned builders can confirm or deny, but I doubt that any house builder is building in suspended wooden ground floors any more. The time and cost involved in insulating under it will be more than building up from the ground and putting a slab of foam under or on top of the concrete. Usually suspended floors are only retro-fitted with insulation where they already exist, i.e. in old houses.

All that is very true, but there is a reason why a timber based garden room rather than concrete is better, and that is a garden room is often in a garden, and peeps don't want (or don't have access) to diggers, mixers, transporting tons of materials into the garden because it makes a mess. Digging a few holes with minimal material to dispose is very mess-free

I recently did a 9 x 3.3 garage on a reinforced concrete pad and materials cost + digger hire was ~£2K. Recent garden room 6.5 x 3.6 on easypads and substantial timber + insulation and floor was ~£2K, so not much in it price wise. (at least as DIY)

 

[Ivor Windybottom]

Yes, there are definitely unexpected costs to building. We now need a new driveway after having trucks, tractors and diggers stomping around the place. It was knackered anyway, but it would have been upsetting if it was all new and lovely.