Laying Flag Paving Slabs

In the latest of our Paving Done Simply series, we're looking at laying flag paving slabs - a simple yet versatile paving option that's available in a wide variety of hues and colours to set the right tone for your landscaping project.

Site Preparation

Let's get started.

  1. Make sure your paving firm, level and well-drained. This base will ensure your patio will last for years to come.
  2. Remove all vegetation and topsoil to an approximate depth of 200mm across the paving area.
  3. Mark out this area with pegs or retaining boards and adjust their height to the required finished surface levels. Remember to allow for water drainage as required.
  4. Make sure that the finished paving surface level is at least 150mm below the level of any damp proof course.
  5. When you're done, rake the surface level for an even depth, before compacting the whole area using a garden roller or tamper.
  6. It's almost time to lay the paving slabs. It's best to start with the full flags laid adjacent to a fixed point. You could use the house or boundary wall as a starting point and to work towards an edge. If that's not possible, just start from a corner on the longest straight edge.
  7. If you are laying more than one size of paving – especially if in a random pattern, or if you are laying a circle or other feature – make sure to you dry lay the flags first the paving slabs fit and match the pattern you're after.
  8. Even if you're just using the one size it's best to pave from number of open packs at once, for a consistent appearance to the finished patio.

Natural Stone Paving – 12 steps to patio perfection

  1. First, dig out the area to a depth of at least 200mm.
  2. When dug out, back fill the area with 150mm of MoT/crusher run, compacted to 100mm.Once the area is prepared, it's time to lay the paving slabs.
  3. The actual mortar bed needs to be individually prepared for each flag dependent on its thickness.
  4. The bed will consist of a semi-dry mortar mix, using 4 parts sharp sand to 1 part cement. Do not use spot bedding for natural stone paving – the flag will not be supported sufficiently.
  5. Are you planning to use mortar joints? To do this, butter the mortar into the receiving edges of already laid flags before pressing a new one. This should form a well filled joint, that can be topped up when pointing. Buttering will also help ensure a consistent joint width.
  6. Once in place, consolidate each flag by tapping them down either with a rubber mallet or placing a piece of softwood between a hammer and the flag. Check the levels as you go.
  7. Lay sandstone / limestone paving onto the full bed of semi-dry mortar, with the chamfered side down, leaving the side with the largest surface area facing upwards.
  8. The hand-dressed edge detail on sandstone and limestone paving has a taper or undercut running towards the back face. The will leave dovetail or reverse wedge-shapes when laid with suitable pointing gaps, which will considerably help keying in the mortar.
  9. Leave the mortar mix to go off for at least 24 hours before pointing.
  10. Point with a wet mortar mix of 4:1 (building sand is more workable), ensuring the gaps between the flags are completely filled. The strength of the pointing is extremely important. Do not let the joints be the weakest part of the paved area.
  11. Take care not to stain the paving surface with any excess mortar. This will be difficult to remove.
  12. A plasticiser can be added to the mortar mix to improve its workability and eliminate air pockets. Cement dyes can also be added to the mix to change the final colouration of your pointing mortar.

Simply Paving offer a jointing compound suitable for use with natural stone flags. For a stress-free process of laying flag paving slabs, just get in touch.

Concrete Paving – is it different from natural stone?

It's similar for the most part, but there are a few differences you need to know.

  1. For concrete paving, the preparation of the site should be carried out using the same methods as when laying natural stone. As they're manmade, thickness won't generally vary for these paving slabs, and the underside will be more consistent.
  2. You can use the same mortar bed composition. However, for light use patios, a screed bed of a sharp sand and cement mix (a ratio of 6:1 is more than adequate) is a simpler alternative.
  3. Concrete paving slabs can also be pointed with a wet mortar mix. Again, be extremely careful not to leave any on the surface of the flag, as this will be almost impossible to remove when set.
  4. For pointing, you can either use a dry mix of sharp sand and cement brushed into the joints or a specifically designed jointing compound.
  5. If pointing with a dry mix, a ratio of 6 parts sharp sand to 1 part cement is recommended.
  6. Lightly water the surface of the flags rather than the pointed joint itself. This will trickle into the joints and hydrate the cement, rather than splash the dry mix over the surface of the flag.

For a simple choice with a vast number of options, flag paving slabs are a solid choice. It allows complete control of the landscaping project – your patio, your way.

We want your landscaping project to be perfect. For advice, assistance, or inspiration, Simply Paving is here to support you at every stage. Give us a call on 0800 032 6306. We would love to hear from you.