A Visit to the Timber Roof Construction Company

Introduction

We had visited Holzbau Hess Company that work with timber for roof construction at prosperita in Windhoek, on Thursday the 28th February 2019.The reason is for us students to learn different construction methods, materials that are used to construct roof structure etc. In term of safety the company is well organized which means housekeeping is well maintained and all machinery are operated by a competent person. Holzbau Hess foreman stated that they are importing timber from Europe (Russia).

Timber as a Construction Materials

Sawn timber are used in construction industry used to make framed structure for residential and form of roof trusses. Holzbau Hess manufacture Glulam timber as per European standards for both residential and commercial development. The foreman stated that Glulam timber are used almost in every kind of construction such as roofs, doors, windows, beams, columns, rafters and also staircase. The foreman stated that they can use Glulam timber to manufacture beams that can be 28 meters maximum in the length and 2.40m in the height and 480mm or 0.48 meters in thickness and curved around with three axes to the minimum radius of 2 meters. Below are some pictures that illustrated how timbers are used in the construction industry. As I observed from the site and what the foreman stated is that Glulam timber are of size of 45cm thicknessx130cm width and 5400cm long, as seen from the above picture and they are getting them from Russia than to Germany than shipped from Walvis bay,

The above picture show the roof structure workshop of Holzbau Hess, whereby they use a Girder trusses made of laminated timber and it has a top weight with compression and the bottom weight where tension occur and there is a diagonal pieces of timber that support the top chord and bottom chord to be stronger and to be not moved from position. There is steel plate at connection of the timber to form connection strong and they also used nails. There is purlins running across fixed to the top chord of Girders by means trusses hangers and the roof sheeting fixed to the purlins and some purlins are running at the bottom of the girders to add some strength. The Girders are run across the shortest length of the workshop and connected to the concrete beam or wall by means of angle plate with bolts and nuts. There is a gap between wall and girder to allow the expansion and contraction of timber.

The how the roof structure of Holzbau Hess workshop whereby they used timber beams and rafters of 228mm in depth and fixed or connected on the same plane and purlins are connected to rafters with trusses hangers where the roof sheeting fixed. There is a timber column which support the beam with two knee brace of timber on an angle connected on the middle of timber column and to the top of beam with a nail plate. There is a short columns with one knee brace fixed to the wall by means of bolts and nuts and such columns support beams and is where the beams connected. Both beams, columns and rafters well-spaced to the particular distance.

Timber Connection Details

The foreman stated that Glulam timber are jointed together by means of finger joint to get it longer and the thickness of finger joint is 12cm to 13cm long. The foreman also stated that some of the timber are used for floor, paneling and ceiling. Timber used for tongue and groove have 12 to 13cm long for jointing purposes. Furthermore the foreman also explained different connection or joint of timber such as, splice connection and use of screws. 30mm long biggest stapled, mortise and tenon joint used together with a wedge to connect timber together, gang nail plate which used where timber meet to add the strength on the joint and knee brace joint which used in connection with screw, mouth joint which additional support to help the knee brace not to jump out or to be in position. We also evaluated the roof trusses of Holzbau Hess workshop how were constructed with timber. The trusses for Holzbau Hess is made up girder trusses that connected to brickwork wall or concrete beam with angle metal plate which is connected to walls in terms of bolts and nuts. On top of girder trusses there is purlins which running horizontal across and fixed to the girder by means of angle plates and is where the roof sheeting connected or fixed with nails.

The foreman highlighted that SA pine has a lot of knot which reducing the strength of timber and they are usually cut out the knot and put a finger joint of 12cm or 13cm with a plate or dowel joint in between and they are usually using them on the inside of the building for ceiling and floors purposes. See some pictures below for the jointing details.

Laminated Timber Manufacturing Process

The foreman stated that Glulam timber have to go through a timber machine to get its square ness and get plained at all four sides before laminated. He further stated that 32mm x 32mm timber have to go through machine to be plained on top and this timber are usually brandering etc. All timber are cutted rectangular before they plained. Laminated timber which are used for rafter purposes are 8cmx120cm. In the workshop for Holzbau Hess there is a working place area where there is clamping for laminating of timber together. The foreman said timber are glued together up in layers and the ideal is to get thickness of timber you require. Air pressure is used during the clamping together of timber. The foreman said they are usually plain them and sanding them off, with the sanding machine. They are also doing practical experiment of calculating the bedding moment of timber to carries the load.

Timber Finishing

Once the timber well plained, they will than sanded off with the sand machine or wood sand paper to get smoothness. The timber are than finished off with the clear paint or wood coat paint, which have to be applied on surface.

Tools and Machinery Used for Laminated Timber Manufacture

In such workshops there is different machine used during laminating of timber, plain and cutting of timber which are used for different purposes. Please find attached pictures of machines.

General

However in such workshop there is a place where they are storing their nails or screw. According to my observations at such place there is rafter hanger’s angle, metal plate for connection of timber together, washer which used in the conjunction with bolts and nuts, different size of nails screw. In addition the foreman stated that they are usually approached by different client. As we found them busy with a frame structure for church in katutura and such frame were treated with wood coat on its surface. The foreman said they have standard grading of timber, C24 and C32 grading. The foreman added that timber has technically moisture content of 10% to 15%.The foreman also added that they are also using timber to make staircase as they are usually requested by the client.

Conclusion

To sum up, construction process is not an easy thing that you can know one day or hours. According to the site visit that we have done it clearly show me that, I need to learn more in terms of timber materials and tools that are used plus the construction methods. The construction have different stage of completion which means all the activities need to follow each other according to the sequence.