Ground Screws

[mrfish]

Many thanks for the superb advice I have received on this site so far. It has been amazing. Has anyone had any experience using ground screws for the foundations of a garden office? Any advice would be greatly appreciated.

[Jeremy Harris]

I looked at a few companies that offered helical pile system, when we were looking to buy a plot where there was a lot of buried archaeology that needed to be protected.  I think that the suppliers we looked at were these:

 

http://www.geologicfoundations.co.uk/design_installation.html/

 

http://www.helicalsystems.co.uk/products/groundscrews

 

and another company (that was very helpful) that used to have a stand at the NSBRC at Swindon, but that I can't remember the name of, and I don't seem to have kept any of the correspondence.

 

All the systems were pretty similar, but there was a difference between the specialisations of the various companies, with some doing mainly things like road signs and gantry foundations, others doing large building foundations and a fair few doing smaller building foundations.

 

Overall I was pretty impressed with the technique, especially as it's been around for 150 years or more, yet seems to not be used as widely as it could be.  The big advantage, apart from the speed and lack of ground work disruption, seems to be that the piles can be driven in quickly and are load-bearing from the moment they are in, so the building ring beam can be bolted on, and construction can start, as soon as all the piles are in and the caps levelled.

Edited June 26, 2017 by JSHarris

[Gone West]

I looked at these when researching for my build. IIRC they were used on a Grand Design where two houses were built on a tight site in London.

 

http://www.screwfast.com/

[ToughButterCup]

8 hours ago, JSHarris said:

[...]

http://www.helicalsystems.co.uk/products/groundscrews

and another company (that was very helpful) that used to have a stand at the NSBRC at Swindon, but that I can't remember the name of, and I don't seem to have kept any of the correspondence.

[...]

 

The company is indeed Helical Systems. Very helpful and prompt when last I contacted them.

[Ashburyselfbuild]

Another one to try is ABC Anchors near Calne Wiltshire http://www.abcanchors.co.uk/

They will also hire the torque motors to drive the screws in if you fancy DIY instllation.

[mrfish]

Many thanks for the replies so far. Would the SIP shed rest directly on the anchors or would I put joists on top and it rest on the joists. Obviously height is a major consideration as I will be losing about 40cm with the sips and the plasterboard inside. 

[Jeremy Harris]

The usual system would be to fit a ring beam to the pile top plates, then the structure on top of that.

 

SIPs panels are fussy about support, and the ring beam must be wide enough to support both the inner and outer skin of the panel, as both are equally load bearing.  Unlike a conventional timber frame, where the compressive load is taken by the vertical studs, with a SIPs panel these loads are taken almost wholly by the two skins, and it's important that both skins share the load evenly.

[Ferdinand]

For a SIPS floor you will also need to take some care with sound management, since a SIP may resonate.

 

Ferdinand

[mrfish]

6 hours ago, JSHarris said:

The usual system would be to fit a ring beam to the pile top plates, then the structure on top of that.

 

SIPs panels are fussy about support, and the ring beam must be wide enough to support both the inner and outer skin of the panel, as both are equally load bearing.  Unlike a conventional timber frame, where the compressive load is taken by the vertical studs, with a SIPs panel these loads are taken almost wholly by the two skins, and it's important that both skins share the load evenly.

I don't suppose you know about centres for the ground screws? If I have to put beams on the screws I might lose too much head height. If was to go the concrete base route how deep would the base need to be?

[PeterW]

6 minutes ago, mrfish said:

I don't suppose you know about centres for the ground screws? If I have to put beams on the screws I might lose too much head height. If was to go the concrete base route how deep would the base need to be?

 

Both of those are related to ground conditions and soil type - what do you have ..??

[mrfish]

10 minutes ago, PeterW said:

 

Both of those are related to ground conditions and soil type - what do you have ..??

If you hit ground it will be sand but for most of it, it will be Victorian brick as a WWII bomb took out the Vic terrace house that was there and they just collapsed the foundations into the basement so if you scratch the topsoil off it is just brick, but, it will extend beyond the old base of the Vic house onto sand. There is about 30cm of clay before the sand.

Edited June 27, 2017 by mrfish
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