Garden Sheds in Borehamwood

Yes, your shed does need a base. This is to give it a solid, level foundation. Open soil will not help with the longevity of the shed itself or the contents within. The best materials to use to make your shed base are concrete, natural stone or wood.

1. How to build a shed base out of paving slabs
   • Mix sand and cement together to make mortar or use a pre-mixed one
   • Use a trowel to lay mortar for 1 slab at a time on the sub-base and lift a damp-sided slab onto the mortar, using a piece of timber and club hammer to tap the slab into position carefully. Continue to lay the first row of slabs
   • Make equally-sized spacers in all the joints in the slabs to ensure they’re the same size, checking it’s level as you go along
   • Next lay slabs along the two adjacent outer edges, filling in the central area row by row
   • Leave the mortar to set according to the instructions or for at least 48 hours before filling in the joints with mortar or paving grout
2. Building a shed base from concrete
   • Create a wooden frame around your shed base area (also called formwork) to stop the concrete from spreading
   • Mix pre-mixed concrete with water or use 1 part cement to 5 parts ballast
   • Wet the sub-base using a watering can with a rose on the end
   • Pour the concrete onto the framed base starting in one corner
   • Push the blade of a shovel up and down in the edges of the concrete to get rid of air bubbles
   • Use a rake to spread the concrete, leaving it around 18mm higher than the top of the frame. Work in sections of around 1-1.m²
   • Compact the concrete using a straight piece of timber that’s longer than the width of the base. Move the timber along the site, hitting it along at about half of its thickness at a time until the surface is evenly ridged
   • Remove excess concrete and level the surface by sliding the timber back and forwards from the edge that you started. Fill in any depressions and repeat until even
   • Run an edging trowel along the frame to round off exposed edges of the concrete and prevent chipping
   • Cover the concrete with a plastic sheet raised on wooden supports to allow slow drying. Weigh it down with bricks
   • Once the concrete is set, you can install your shed and remove the wooden frame with a crowbar

1. Plan your shed base You must have a sturdy base for your shed, otherwise the frame won’t stand properly and could stop the door from opening. Decide whether you’re going to have:
   • A concrete base laid on hardcore
   • Concrete slabs on sharp sand
   • Treated wood beams on hardcore or shingle
   • An interlocking plastic system
   All bases should be laid on firm, level ground as far as possible.
2. Treat wood with preservative To help your shed last as long as possible, you should coat all the wooden parts with timber preservative before you put it together.
3. Put the shed floor together Some will need more assembly than others, but you need to make sure that the floor panel is attached to the joists; follow the manufacturer’s instructions for the correct spacing.
4. Put up the shed walls
   • Mark the centre point of each wall on its bottom edge, then do the same for the shed floor so you can line them up together.
   • Stand the gable end on the base and line it up. Check that it’s vertical with a spirit level – you might need someone to support the panel while you do this. Use a temporary holding batten to keep it in place.
   • Fix a side panel to the gable end panel with countersunk screws, then add the second side panel in the same way.
   Don’t attach the panels to the floor until you’ve fitted your shed roof.
5. Fit the roof
   • If the shed comes with a support bar, put this in position before you put the roof panels in.
   • Nail the roof panels in place, ensuring there’s a parallel and equal overlap at each end.
   • Roll out some roofing felt from front to back, leaving a 50mm overlap at each side. Secure it with clout-headed felt tacks at 100mm intervals.
   • Apply mastic sealant to the outside corners, then fix each corner trim with 30mm nails.
   • Add the fascias and finials, predrilling 2mm holes to avoid splitting the wood. Nail them through the felt into the shed using 40mm nails.
6. Add the shed windows
   • Slide each windowsill into the tongue and groove cut out, then put the window cover strip in position, fixing it to the vertical framing.
   • From inside the shed, put the glazing sheets into the window rebates, making sure the bottom edge of the glazing sheets sit on the outside of the sill.
   • Fix the window beading on the top and sides with 25mm nails.
7. Fix the walls to the floor Before you do anything, make sure you check that the centre marks on the walls line up with the marks on the shed floor. Then fix the wall panels to the floor with 50mm screws, aligning them with the joists.
And that’s it! But if you’re not confident in building a shed yourself, there are plenty of professionals available who will be happy to help.