Trying my hand at a summer house.

[BJM]

Hi guys. I like to try anything and everything. I've done a lot of work around the house from landscaping to converting my attic.

 

I've decided to upgrade my garden shed to something a little more modern, and would like to make a timber frame structure.

 

my house on a hill and my back garden is surrounded on 2 sides with retaining walls 3 metres in height. The retaing walls are backfilled to the top.

I imagine that the walls would have been structural designed and built, and adequate drainage would be installed 

The backfilled soil was slopping from the house down to the bottom of the garden.

I leveled the ground taking the slope out and made a 2 level patio with the lower level being 5 metres wide and 6 metres long.

I left a 4 to 6" gap at the bottom and filled with small stones for drainage.

I used 600 x 600 x 50 slabs and layed them apon stone dust and cement.

 

I am not experienced.  Only what I've recently read about retaining walls, surcharge and drainage.

I have removed the slope and quite alot of soil came out. 30 tonne of material was taken for recycling from the whole project. I put around 10 tonne back in for the patio, steps and wall feature. There must be alot of weight behind the retaining walls. If the back wall is 3 m high and 5 m wide then there's about 15 tonne per metre, but this is less than would have originally been

 

I want to build a timber framed structure at the bottom of the garden 4.8m x 2.7m.

I didn't know at the time of building the patio that I was going to want to build a structure. I don't know if I can use my patio as a base or if I need to make a new concrete pad.

 

I want to know if its structurally safe to do this. with it being a garden backfilled behind a retaining wall.

[MikeSharp01]

Welcome to THE forum for people like us.

 

Probably need some pictures to fully understand what you are saying but are you saying that the retaining walls have soil on your side and nothing on the other side?

[BJM]

Yes that's correct. There is nothing on the other side of the walls. There's soil on my side. A garden on one side and a road on the other side

[Mr Punter]

I doubt is you will easily be able to establish what loadings the retaining wall can support without knowing the build up, including foundations but if it has been there for some years and is not showing any signs of failure you could assume that it will not suddenly deteriorate.

 

I doubt a concrete base and timber framed summerhouse will make much difference to the loadings.  If the wall is going to fail it could do so in any case.  It is not likely to suddenly collapse.

[BJM]

Just want to ask these questions now before I start applying anymore surcharge behind the wall. I doubt I'll ever know the make up of the walls and there load rating. I just want to make sure what ever I do want cause any issues down the road.