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By Cara Mackay on 11 Jun 2019

What kind of base do you need for a Summerhouse?

So, let’s get right to it then… here’s everything you need to know about prepping the base for your Summerhouse.

“Hang on? What?

You need a base for a Summerhouse? What’s that all about then?

Surely a Summerhouse has a floor, right? So can’t you just plonk it in the garden and have your pals round for wine time?”

Easy there Janice, not quite. It’s really important that you have a base installed BEFORE your Summerhouse arrives, and here’s why…

Please note: We highly advise you obtain landscaper quotes for base work before ordering your Gillies and Mackay building to obtain a full and clear picture of project costs.

Why do I need a base for my Summerhouse?

Summerhouses typically weigh around 1 – 2 tonnes, depending on what you want to put in them. And all that hefty body needs a solid base to keep it steady. If we don’t prepare a proper base for her then she’ll sink, subside and generally get a bit grumpy about the whole thing. And nobody wants a grumpy Summerhouse!

A solid Summerhouse base also ensures the building remains level, this stops any carry on with the doors falling out of square. I tell you, the number of times I’ve had to send Grant out to adjust a contracted door and he gets there and it has nothing to do with contraction, it’s because their base isn’t substantial enough.

Luckily Grant’s really nice and shims it up for them. However, it will save everyone’s time if we get it right from the start. So…

How do I build a Summerhouse Base?

Well, let’s have a wee think about what’s already there.

Typically, you’ll have an area in your garden that makes you think… “Ooh, that would be just spot on for our Summerhouse, that bit there!”.

If you’re lucky you’ll be looking at a nice flat lawn, meaning it’s an easy, straightforward process, starting with a little excavation…

Step 1: Dig down to firm ground

what kind of base do i need for a summerhouse pic 01
Dig down to firm ground

Isn’t she pretty?

What I really love about this particular site, is that the base layer (J.R. Evans) has taken the measurements of the Summerhouse alone and marked out the maximum area that is required.

It’s really important that the Summerhouse base is seen as just that. A base for the Summerhouse and not as part of the overall landscaping of the Garden.

Making sure you prepare a base to the measurements required will ensure that the slabs remain underneath the Summerhouse and DO NOT exceed the perimeter of the Summerhouse.

In doing this you allow all the water that comes off the roof of the Summerhouse to run clear of the base and doesn’t invite the water to lay logged on the slabs.

Don’t fret if you would like slabs around or leading up to your Summerhouse, I will talk about that later.

Once you have marked out your size, you need to dig down to solid ground. This basically means past the topsoil/turf and to the point where the ground is really firm. Usually about 6”/150 mm.

Making sure you keep your basic level, as you don’t want it slopping before you’ve even started.

Step 2: Fill and compact Type 1 Hardcore.

Lay Type 1 Compact Hardcore* – this provides the stability and hold required for the slabs and Summerhouse itself. You should expect to fill up the excavated area by 4”/100 mm or so with the hardcore.

You’ll need a whacker to get it level:

what kind of base do i need for a summerhouse pic 02
Fill with Type 1 Hardcore and compact down to level

Looking good!!

*Type 1 Hardcore: stone/rock blended material used as a sub-base. Specifically used for creating an even surface when building driveways, roads, footpaths or bases.

Step 3: Laying the slabs

So your base area has compacted T1 Hardcore in it and it’s ready for the next stage, laying the slabs.

Slab laying isn’t rocket science but if you’re not persistent with the level then it can get tricky quickly.

Ideally, you want to use building sand to allow the slabs a tight compact surface to rest upon.

The cornerstones to your Summerhouse slabbed base would definitely benefit from being concreted in place. It just keeps everything neat and in square, so start with them okay.

You may also need to play around with them a little as you maintain your level, but eventually, it’ll look something like this…

A Pristine Summerhouse Base

what kind of base do i need for a summerhouse pic 03
Summerhouse base done right ♥️


This is a pristine slabbed area, perfect for a 12’ x 10’ Rannoch Summerhouse to sit flush on top.

Do you like what the base layer has done with the gravel surround? Do you know WHY he has done this?

Well. When the water runs off the Summerhouse we want it to go as far away as possible from the Summerhouse. What the gravel surround does is, it acts as a soakaway for all the rain. Pure brilliant!

We recommend you leave a neat 6”/150 mm gap between the summerhouse base and any other continuing landscape (deck, decorative slabs, grass, etc.).

what kind of base do i need for a summerhouse pic 04
150mm Gravel Gap around Summerhouse

You can see in this picture there are steps leading to the Summerhouse, gravel, then the slabbed base tucked neatly underneath the Summerhouse.

It’s important to say also, that the area between the slabs and the bottom of the doors is made up of bearers, then floor joists, then flooring. This allows the cross structure to continue supporting the Summerhouse for bearing weight and also allows the Summerhouse floor to breathe.

I’m really glad we’ve had this chat you know. It’s possible you won’t want to do all this work yourself though. You’ll likely employ a highly skilled landscaper, like Homescape, to do it all for you. But at least you now know why your Summerhouse needs a base and how to do it.

All good?


All my Shed Love,

Natty x

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