Monday 3 July 2017

Entrances made by cutting bricks

We no longer recommend that people make an entrance to an internal nest box by cutting bricks, unless you know what you are doing. This is because of a number of experiences of getting the wrong size, both too small and too big. Here is an example of how to do it properly.

The tolerences for the smaller dimension of a Swift entrance are rather tight. Too big will let Starlings in and too small will make it difficult for Swifts. The longer dimension of the entrance is not critical. Perhaps a minimum of 50mm, often set at 65mm and bigger than this is OK.

Starlings can squeeze into 30mm. The smallest dimension that a Swift can squeeze into is ~25mm. So we recommend 28mm ± 1mm

In Kev Gray's own words:

"... I ended up cutting a very accurate slot to your dimensions into the top face of a matching house brick. I used a stone cutter in my 9 inch grinder, it didn't take many minutes, I bonded a slate lid over the top of the cut out and fitted the whole brick. If one uses mortar to fashion the 4th side of the entrance, there is much scope for getting it wrong. Prefabricating the entrance ensures the correct size.

First we cut the brick out of the wall, we used a battery powered masonry drill and bit and just drilled a series of holes all the way around the brick and it came out quite easily.

The hole was then tidied up with a bolster chisel and the swift brick fitted.

A long masonry bit was positioned in the centre of the Swift slot from the outside of the wall and guide hole was then drilled through the inner wall, the wall on the other side of the cavity, this is usually breeze block and drills very easily.

From inside the loft.

The guide hole previously drilled in the breeze block is then used to guide a large diameter masonry hole cutter, if it's breeze block it cuts quite easily, if you don't have access to a hole cutter you could use drill a series of small holes drilled in a circle and chisel the middle out.

When the hole is finished measure from the internal face of the breeze block back to the inside face of the Swift brick to establish the length of soil pipe required.

The pipe is just ordinary 110mm soil pipe, anything similar would do, you can get it from most DIY stores., I can be cut with a hand saw and positioned into the hole so that it butts up to the new swift brick, take care if the mortar is still soft as you may dislodge the swift brick, it's better to leave it time to set. When the pipe is in position use some mortar to fill in any gaps and holes that may be in the swift brick to make a nice smooth passage without any sharp edges. Also it's a good idea to put a bed of mortar along the bottom run of the soil pipe as this will help the Swifts have a bit more grip onto what would otherwise be a very slippery surface. In fact it's a good idea to give the inside of the soil pipe a good roughing out with some course sandpaper before putting it into position as this will help the mortar stick.

As mentioned earlier, I made up a couple of boxes from some spare 18mm chipboard floorboard because that what I had handy, but you could use something much thinner maybe some plywood. Bill Murrells recommend internal dimensions of W 200 x L 300 x H 150 for the box and that is what I went with.

Removing a brick
Components of the entrance brick, before cutting
Relative positioning of soil pipe and entrance brick
The completed entrance
A view from the inside

No comments:

Post a Comment