01
What size ground screws do I need?
Ground screw size depends on the weight and layout of the building, the ground, the screw shape and how the frame will fix to it. The building footprint alone is not enough to choose a structural screw.
Ground screw size guide
Size and depth,
without guesswork.
Length is only one part of the answer. The building weight, ground, screw diameter and shape, installation depth and fixings all affect the right size.
Quick answer
What determines ground screw size?
01
Building load
How much weight and uplift reaches each support point.
02
Ground conditions
Soft, hard, filled or obstructed ground can change the screw size and depth.
03
Screw shape
Length, diameter, wall thickness and the lower screw shape all affect performance.
04
Fixings & installation
The head or bracket must suit the building, and the screw needs to be installed correctly.
Size vs depth
Longer is not automatically better.
Ground screw length is often the first number people compare, but it cannot be separated from the rest of the system. Two screws of the same length can have different shaft, wall, helix, tip and head configurations.
Installation depth should not be copied from a generic table. The right depth depends on the screw, the load and the ground found on site.
For structural work, use the product data and calculations for the actual job rather than a rule of thumb.
By application
The application changes the question.
Decking
Deck size, beam and joist spans, finished level, expected use and ground conditions all affect the screw layout and size.
Application guideSheds & cabins
The base-frame layout, building weight and floor support strategy matter more than the label “shed” or “log cabin”.
Application guideGarden rooms
Frame layout, floor spans, openings, roof weight and the ground should be considered together before choosing the screws.
Application guideExtensions & larger structures
Larger buildings normally need more detailed load calculations, Building Control information and connection details.
Application guide01
Work out the loads
Understand what the building puts onto each support point.
02
Check the site
Look at the ground, levels, services and machinery access.
03
Choose the screw
Select the size, depth and fixings using the product data and job information.
Size & depth FAQs
Ground screw sizing questions, answered.
Direct answers on length, depth, diameter, capacity and why the building footprint alone cannot select the screw.
02
How deep do ground screws need to be?
There is no single depth that works for every job. The depth depends on the screw type, the load it needs to carry and what the ground is like. The final depth should be based on the actual project and site.
03
Does a longer ground screw hold more weight?
Not automatically. Length is only one part of the system. Shaft diameter, helix or tip geometry, wall thickness, ground conditions, installation and load direction all affect foundation performance.
Understand load capacity04
What diameter ground screw do I need?
A larger diameter can change how much load a screw can carry, but diameter is only one part of the design. Length, wall thickness, lower screw shape, ground conditions and the building loads all matter too.
See specification factors05
Can I choose ground screw size from a garden room or deck size?
The building dimensions are useful, but they do not tell you how much weight reaches each support, how far beams span or what the ground is like. Work out where the building needs support before choosing the screw size.
See how support loads are assessedNeed help choosing?
Start with the building and the site.
Send the project details and we can help work out the right screw size and foundation layout.