Our Big Bug House – Part 2

Welcome back for part 2, if you missed part one you can see it by clicking here.

In part one of this series, we looked at the beneficial species that bug houses help to attract to the garden, where to site it and the materials we used to build the project.

In this post, we will look at constructing the foundation and creating a habitat for frogs, other amphibians and beetles.

Making the foundation
Whilst it’s perfectly valid to just build your bug house straight on the ground, this allows ground moisture into the structure, which in turn causes the wood to rot – excellent for bugs, fungi and biodiversity, less good if you want something to last more than three or four years and remain safe especially if you have small people running around.

Anything other than the smallest bug house needs a good level foundation to support it, keep it level and make sure it’s not going to topple over. For this reason, and because we wanted our grand design to last a good number of years, we decided to put in some concrete and brick foundations to raise the wood off the ground. This limits the amount of moisture rising into the woodwork and has the added benefit of creating a void under the bug house that can be used to create a habitat for amphibians. To simplify the casting of the concrete portion of the foundation we made a temporary frame work out of old pallet wood and other scraps we had lying around. This allowed us to get everything square and level before we dug holes or mixed concrete.

We marked out the location for the holes using the frame work as a guide and ground marking paint this allowed us to check we had got the position right – Measure twice dig once!

The framework was positioned and levelled with the bottom of the holes filled with broken floor tiles, brick and stone. Basically anything that would take up a bit of volume whilst allowing the frame to be levelled. Finally the concrete was mixed and poured into each void. The easiest way of making the concrete is to use pre prepared ‘post fix’ which has everything needed dry mixed in one bag. All you need to do is add water and mix thoroughly. We used a scrap piece of wood to level off the top surface of the concrete on each void.

The concrete was left to set for several days before the framework was removed and the gaps back filled with soil.

Once the concrete had fully set up (we left it until the following weekend) we mortared the block paving stones in place on top. These are really the only bit that will be visible once the ground settles in and the wild plants grow back.

We left the mortar to dry for another week prior to adding weight on top of it.

Creating an environment from slugs and toads
Between the concrete pillars, we created a loose, open pile of stone, broken terracotta pots, slate and dead rotting wood and leaves to make a habitat for beetles and amphibians.  Make sure you leave some routes in and out, as well as some chambers for frogs and toads to live in.

Building the stack

Once we were happy that the foundation concrete and mortar had cured well enough to bear weight, we started building the stack of pallets by placing the first one in situ and stuffing with straw.

Each pallet was assembled in turn and for safety reasons, we decided to screw the pallets together as we went to prevent any chance they would slip or topple. Each pallet was backfilled with straw to provide insulation and plenty of habitat for any bugs or other small creatures that made their way into the centre.

We used a pallet with more slats on the top to provide a firm base for the roof structure.

Building the roof
We wanted a green roof (roof planted with living plants) on the bug house. Typically these would be made with a flat gently sloping roof to prevent the soil washing off in heavy rain. We didn’t like that style and wanted to try a peaked roof for aesthetic reasons so we had to play with the angles to find a good compromise between the ‘look’ and the angle to allow the soil to stay in place. We used a stack of bricks and batten wood to try out various angles and settled on the one shown in the photo below.

A central roof support was screwed into position. This was made long enough to have an overhang at the front and rear of the bug house.

We then cut battens to the right length to provide a good overhang to allow water to run clear of the sides, to avoid rotting the habitats and the pallets.

These were also screwed in place. We prefilled the void under the roof with bug friendly objects including broken roof tiles, pine cones, and dried grasses and more straw to provide insulation. This was a lot easier between the rafters rather than trying to pack it from the ends after the roof boards are put on.

The roof boards were cut from OSB (Oriented Strand Board) and were screwed to the rafters. Because of the angles of the roof the edges didn’t naturally butt together well. A plane was handy here to get everything neat and tidy so as the roof felt didn’t get damaged by sharp edges.

To waterproof the roof, we added roofing felt and nailed this on with a special flat head nail designed for the purpose, called a clout nail. Using a heat gun to soften the edges of the felt allows a nice tight corner to be achieved without splitting the roofing felt.

That’s it for now, I’ll see you next week for the final step in the process of our Big Bug House. Remember to let us see your projects for beneficial habitats.